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Automotive Technology, Fourth EditionJames Halderman
DIESEL ENGINE OPERATION AND
DIAGNOSIS
19
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
ObjectivesObjectives• The student should be able to:
– Prepare for ASE Engine Performance (A8) certification test content area “C” (Fuel, Air Induction, and Exhaust Systems Diagnosis and Repair).
– Explain how a diesel engine works.– Describe the difference between direct
injection (DI) and indirect injection (IDI) diesel engines.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
ObjectivesObjectives• The student should be able to:
– List the parts of the typical diesel engine fuel system.
– Explain how glow plugs work. – List the advantages and disadvantages of a
diesel engine.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
DIESEL ENGINESDIESEL ENGINES
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
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Diesel EnginesDiesel Engines• Fundamentals
– Rudolf Diesel perfected the compression ignition engine in 1892
– Heat created by compression ignites the fuel
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Diesel EnginesDiesel Engines• Fundamentals
– Requires compression ratios of 16:1 and higher
– Heat of compression: incoming air is compressed until its temperature reaches about 1,000 。 F (540 。 C)
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
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Diesel EnginesDiesel Engines• Fundamentals
– Fuel is injected into the cylinder and ignited by hot air
– Fuel produces power as it burns
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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© 2011 Pearson Education, Inc.All Rights Reserved
Diesel EnginesDiesel Engines• Fundamentals
– Heavier and stronger than the same size gasoline-powered engine
– Fuel system with a precision injection pump and individual fuel injectors
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Diesel EnginesDiesel Engines• Fundamentals
– Pump delivers fuel to injectors at a high pressure and at timed intervals
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
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Diesel EnginesDiesel Engines• Fundamentals
– Each injector sprays fuel into the combustion chamber at the precise moment required for efficient combustion
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Figure 19-1 Diesel combustion occurs when fuel is injected into the hot, highly compressed air in the cylinder.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Figure 19-2 A typical injector pump type of automotive diesel fuel–injection system.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Diesel EnginesDiesel Engines• Advantages and Disadvantages
– Advantages include:• More torque output• Greater fuel economy• Long service life
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Diesel EnginesDiesel Engines• Advantages and Disadvantages
– Disadvantages include:• Engine noise• Exhaust smell• Cold weather startability
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
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Diesel EnginesDiesel Engines• Advantages and Disadvantages
– Disadvantages include:• Vacuum pump • Heavier than a gasoline engine
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
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Diesel EnginesDiesel Engines• Advantages and Disadvantages
– Disadvantages include:• Fuel availability• Extra cost compared to a gasoline engine
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
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Diesel EnginesDiesel Engines• Construction
– Constructed heavier than gasoline engines because of the tremendous pressures that are created in the cylinders during operation
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel EnginesDiesel Engines• Construction
– Torque output is often double or more than the same size gasoline-powered engines
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Chart 19-1 Comparison between a typical gasoline and a diesel engine.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Figure 19-3 A Cummins diesel engine as found in a Dodge pickup truck. A high-pressure pump (up to 30,000 PSI) is used to supply diesel fuel to this common rail, which has tubes running to each injector. Note the thick cylinder walls and heavy-duty construction.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Figure 19-4 A rod/piston assembly from a 5.9 liter Cummins diesel engine used in a Dodge pickup truck.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel EnginesDiesel Engines• Air-Fuel Ratios
– Air-fuel mixture of a diesel can vary from as lean as 85:1 at idle to as rich as 20:1 at full load
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Diesel EnginesDiesel Engines• Air-Fuel Ratios
– Higher air-fuel ratio and the increased compression pressures make the diesel more fuel efficient than a gasoline engine
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Diesel EnginesDiesel Engines• Air-Fuel Ratios
– Speed and power are not controlled by the amount of air entering the cylinders, so the engine always has enough oxygen to burn the fuel in the cylinder and will increase speed (and power) when additional fuel is supplied
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel EnginesDiesel Engines• NOTE: Many newer diesel engines are
equipped with a throttle valve. This valve is used by the emission control system and is not designed to control the speed of the engine.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel EnginesDiesel Engines• Indirect and Direct Injection
– Indirect injection (abbreviated IDI) diesel engine
• Fuel is injected into a small prechamber connected to the cylinder
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel EnginesDiesel Engines• Indirect and Direct Injection
– Indirect injection (abbreviated IDI) diesel engine
• Initial combustion takes place in the prechamber
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel EnginesDiesel Engines• Indirect and Direct Injection
– Indirect injection (abbreviated IDI) diesel engine
• Slowed rate of combustion tends to reduce noise
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel EnginesDiesel Engines• Indirect and Direct Injection
– Direct injection (abbreviated DI) diesel engine
• Fuel is injected directly into the cylinder
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel EnginesDiesel Engines• Indirect and Direct Injection
– Direct injection (abbreviated DI) diesel engine
• The piston incorporates a depression where initial combustion takes place
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel EnginesDiesel Engines• Indirect and Direct Injection
– Direct injection (abbreviated DI) diesel engine
• Generally more efficient than indirect injection engines
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel EnginesDiesel Engines• Indirect and Direct Injection
– Direct injection (abbreviated DI) diesel engine
• Tend to produce greater amounts of noise
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Figure 19-5 An indirect injection diesel engine uses a prechamber and a glow plug.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Figure 19-6 A direct injection diesel engine injects the fuel directly into the combustion chamber. Many designs do not use a glow plug.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel EnginesDiesel Engines• Diesel Fuel Ignition
– Fuel is injected into the air charge heated by compression to a temperature greater than the ignition point of the fuel or about 1,000°F (538°C)
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel EnginesDiesel Engines• Diesel Fuel Ignition
– Expanded gases force the piston to rotate the crankshaft
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel EnginesDiesel Engines• Diesel Fuel Ignition
– A four-stroke diesel engine requires two rotations of the crankshaft to complete one cycle
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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THREE PHASESTHREE PHASESOF COMBUSTIONOF COMBUSTION
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Three Phases of CombustionThree Phases of Combustion• Ignition delay• Rapid combustion• Controlled combustion
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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FUEL TANKFUEL TANKAND LIFT PUMPAND LIFT PUMP
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
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Fuel Tank and Lift PumpFuel Tank and Lift Pump• Parts Involved
– Fuel tank on a vehicle with a diesel engine differs from gasoline engine in the following ways:
• Filler neck is larger for diesel fuel
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Fuel Tank and Lift PumpFuel Tank and Lift Pump• Parts Involved
– Fuel tank on a vehicle with a diesel engine differs from gasoline engine in the following ways:
• Nozzle size is 15/16 in. (24 mm) instead of 13/16 in. (21 mm) for gasoline filler necks
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Fuel Tank and Lift PumpFuel Tank and Lift Pump• Parts Involved
– Fuel tank on a vehicle with a diesel engine differs from gasoline engine in the following ways:
• No evaporative emission control devices or a charcoal (carbon) canister
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Fuel Tank and Lift PumpFuel Tank and Lift Pump• Parts Involved
– Fuel tank on a vehicle with a diesel engine differs from gasoline engine in the following ways:
• Diesel fuel is not as volatile as gasoline
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Fuel Tank and Lift PumpFuel Tank and Lift Pump• Parts Involved
– Fuel tank on a vehicle with a diesel engine differs from gasoline engine in the following ways:
• Diesel vehicles do not have evaporative emission control devices
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Fuel Tank and Lift PumpFuel Tank and Lift Pump• Parts Involved
– Diesel fuel is usually drawn from the fuel tank by a lift pump
– Lift pump delivers fuel to the injection pump
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Fuel Tank and Lift PumpFuel Tank and Lift Pump• Parts Involved
– Between the fuel tank and the lift pump is a water-fuel separator
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Fuel Tank and Lift PumpFuel Tank and Lift Pump• Parts Involved
– Float inside the separator is connected to a warning light on the dash that lights if the water level is too high
– Separator is often part of the fuel filter assembly
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Fuel Tank and Lift PumpFuel Tank and Lift Pump• NOTE: Water can cause corrosive
damage and wear to diesel engine parts because it is not a good lubricant. Water cannot be atomized by a diesel fuel injector nozzle and will often “blow out” the nozzle tip.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Figure 19-7 A fuel temperature sensor is being tested using an ice bath.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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INJECTION PUMPINJECTION PUMP
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Injection PumpInjection Pump• Need for High-Pressure Fuel Pump
– Injection pump used to increase pressure of the fuel
– Lift pump is a low-pressure, high-volume pump
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Automotive Technology, Fourth EditionJames Halderman
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Injection PumpInjection Pump• Need for High-Pressure Fuel Pump
– High-pressure injection pump is a high-pressure, low-volume pump
– Injection pumps are usually driven by a gear off the camshaft at front of engine
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Injection PumpInjection Pump• Need for High-Pressure Fuel Pump
– Fuel is fed from fill port to high-pressure chamber
– If distributor type injection pump is used, fuel is forced out of the injection port to the injector nozzle through the high-pressure line
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Injection PumpInjection Pump• NOTE: Because of the very tight
tolerances in a diesel engine, the smallest amount of dirt can cause excessive damage to the engine and to the fuel-injection system.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Figure 19-8 A typical distributor-type diesel injection pump showing the pump, lines, and fuel filter.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Injection PumpInjection Pump• Distributer Injection Pump
– High-pressure pump assembly with lines leading to each individual injector
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Injection PumpInjection Pump• Distributer Injection Pump
– High-pressure lines between distributor and injectors must be the exact same length
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Injection PumpInjection Pump• Distributer Injection Pump
– High-pressure fuel causes injectors to open– The injection pump itself creates the
injection advance needed for engine speeds above idle, then the fuel is discharged into the lines
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Injection PumpInjection Pump• NOTE: The lines expand some during an
injection event. This is how timing checks are performed. The pulsing of the injector line is picked up by a probe used to detect the injection event similar to a timing light used to detect a spark on a gasoline engine.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Figure 19-9 A schematic of Standadyne diesel fuel–injection pump assembly showing all of the related components.
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Injection PumpInjection Pump• High-Pressure Common Rail (HPCR)
– Diesel fuel under high pressure is applied to the injectors
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Injection PumpInjection Pump• High-Pressure Common Rail (HPCR)
– Injectors are opened by a computer controlled solenoid
– Combustion process can be precisely controlled to provide maximum engine efficiency with the lowest possible noise and exhaust emissions
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Figure 19-10 Overview of a computer-controlled high-pressure common rail V-8 diesel engine.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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HEUI SYSTEMHEUI SYSTEM
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Heui SystemHeui System• Principles of Operation
– Ford 7.3 and 6.0 liter (and Navistar) diesels use a hydraulic electronic unit injection (HEUI) system
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Heui SystemHeui System• Principles of Operation
– Components include:• High-pressure engine oil pump and reservoir
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Heui SystemHeui System• Principles of Operation
– Components include:• Pressure regulator for the engine oil
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Heui SystemHeui System• Principles of Operation
– Components include:• Passages in the cylinder head for flow of fuel
to the injectors
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Heui System Heui System • Operation
– The system functions as follows:• Fuel is drawn from the tank by the tandem
fuel pump and circulated at low pressure through the fuel filter/water separator/fuel heater bowl, then directed back to the fuel pump where fuel is pumped at high pressure into the cylinder head fuel galleries
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Heui System Heui System • Operation
– The system functions as follows:• Injectors hydraulically actuated by engine oil
pressure from the high-pressure oil pump are fired by the powertrain control module (PCM). The PCM is the control system for the fuel injectors and the injectors are fired based on sensor inputs received by the PCM.
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Figure 19-11 A HEUI injector from a Ford PowerStroke diesel engine. The O-ring grooves indicate the location of the O-rings that seal the fuel section of the injector from coolant and from the engine oil.
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Heui System Heui System • Operation
– Five O-rings keep fuel and oil from mixing or escaping
– Three external O-rings should be replaced if they fail
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Heui System Heui System • Operation
– Injectors must be replaced if the two internal O-rings fail
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Heui System Heui System • Operation
– The most common symptoms of injector O-ring trouble include:
• Oil getting in the fuel• Fuel filter element turning black
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Heui System Heui System • Operation
– The most common symptoms of injector O-ring trouble include:
• Long cranking times before starting• Sluggish performance
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Heui System Heui System • Operation
– The most common symptoms of injector O-ring trouble include:
• Reduction in power• Increased oil consumption
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DIESEL INJECTOR DIESEL INJECTOR NOZZLESNOZZLES
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Diesel Injector NozzlesDiesel Injector Nozzles• Parts Involved
– Parts of a diesel injector nozzle include:• Heat shield• Injector body
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Diesel Injector NozzlesDiesel Injector Nozzles• Parts Involved
– Parts of a diesel injector nozzle include:• Diesel injector needle valve• Injector pressure chamber
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Diesel Injector NozzlesDiesel Injector Nozzles• Diesel Injector Nozzle Operation
– Electric solenoid on the nozzle is computer controlled and opens to allow fuel to flow into the injector pressure chamber
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Diesel Injector NozzlesDiesel Injector Nozzles• Diesel Injector Nozzle Operation
– Fuel flows down a fuel passage in the injector body and into the pressure chamber
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Diesel Injector NozzlesDiesel Injector Nozzles• Diesel Injector Nozzle Operation
– High fuel pressure forces the needle valve upward, compressing the needle valve return spring and forcing the needle valve open
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Diesel Injector NozzlesDiesel Injector Nozzles• Diesel Injector Nozzle Operation
– Fuel is discharged into the combustion chamber in a hollow cone spray pattern
– Fuel that leaks past the needle valve returns to the fuel tank
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Figure 19-12 Typical computer-controlled diesel engine fuel injectors.
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Figure 19-13 A Duramax injector showing all the internal parts.
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GLOW PLUGSGLOW PLUGS
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Glow PlugsGlow Plugs• Purpose and Function
– Heating element that uses 12 volts from the battery and aids in the starting of a cold engine by providing heat to help the fuel to ignite
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Figure 19-14 A glow plug assortment showing the various types and sizes of glow plugs used. Always use the specified glow plugs.
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Glow PlugsGlow Plugs• Operation
– Glow plugs are controlled by the powertrain control module
– Glow plugs are turned on or pulsed on or off depending on engine temperature
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Glow PlugsGlow Plugs• Operation
– The PCM keeps the glow plug turned on after the engine starts, to reduce white exhaust smoke and to improve idle quality after starting
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Glow PlugsGlow Plugs• Operation
– “Wait to start” lamp (if equipped) will light when the engine and the outside temperatures are low to allow time for the glow plugs to get hot
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Figure 19-15 A schematic of a typical glow plug circuit. Notice that the glow plug relay and intake air heater relay are both computer controlled.
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Glow PlugsGlow Plugs• Heated Inlet Air
– Some diesel engines use an electrical heater wire to warm the intake air to help in cold weather starting and running
?
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Figure 19-16 A wire-wound electric heater is used to warm the intake air on some diesel engines.
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ENGINE-DRIVENENGINE-DRIVENVACUUM PUMPVACUUM PUMP
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Engine-Driven Vacuum PumpEngine-Driven Vacuum Pump• Most diesels in cars and light trucks are
equipped with an engine-driven vacuum pump to supply the vacuum components such as:– Exhaust gas recirculation (EGR) valve
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Engine-Driven Vacuum PumpEngine-Driven Vacuum Pump• Most diesels in cars and light trucks are
equipped with an engine-driven vacuum pump to supply the vacuum components such as:– Heating and ventilation blend– Air doors
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DIESEL FUEL HEATERSDIESEL FUEL HEATERS
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Diesel Fuel HeatersDiesel Fuel Heaters• Help prevent power loss and stalling in
cold weather• Placed in the fuel line between the tank
and the primary filter
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ACCELERATOR PEDALACCELERATOR PEDALPOSITION SENSORPOSITION SENSOR
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Accelerator Pedal Position Sensor Accelerator Pedal Position Sensor • A throttle-by-wire system uses an
accelerator pedal position (APP) sensor• To ensure safety, it consists of three
separate sensors that change in voltage as the accelerator pedal is depressed
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Accelerator Pedal Position Sensor Accelerator Pedal Position Sensor • Voltage output of each sensor is
compared to a standard voltage to check for errors
• Engine and vehicle speeds are often reduced if errors are found
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Figure 19-17 A typical accelerator pedal position (APP) sensor uses three different sensors in one package with each creating a different voltage as the accelerator is moved.
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DIESEL ENGINEDIESEL ENGINETURBOCHARGERSTURBOCHARGERS
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Diesel Engine TurbochargersDiesel Engine Turbochargers• Turbocharged Diesels
– Greatly increases engine power – The turbine wheel spins as exhaust gas
flows out of the engine and drives the turbine blades
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Diesel Engine TurbochargersDiesel Engine Turbochargers• Turbocharged Diesels
– The turbine spins the compressor wheel at the opposite end of the turbine shaft, pumping air into the intake system
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Figure 19-18 A Cummins diesel turbocharger is used to increase the power and torque of the engine.
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Diesel Engine TurbochargersDiesel Engine Turbochargers• Air Charge Cooler
– Cools compressed air to further raise the air density
– More power can be produced by the engine
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Figure 19-19 An air charge cooler is used to cool the compressed air.
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Diesel Engine TurbochargersDiesel Engine Turbochargers• Variable Turbocharger
– Used for boost control– Boost pressure is controlled independent of
engine speed and a wastegate is not needed
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Diesel Engine TurbochargersDiesel Engine Turbochargers• Variable Turbocharger
– Adjustable vanes– Vane position control solenoid valve
advances the unison ring’s relationship to the turbine and thereby articulate the vanes
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Diesel Engine TurbochargersDiesel Engine Turbochargers• Variable Turbocharger
– Solenoid actuates a spool valve that applies oil pressure to either side of a piston
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Diesel Engine TurbochargersDiesel Engine Turbochargers• Variable Turbocharger
– Oil flow has three modes:• Apply moves the vanes toward a closed
position
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Diesel Engine TurbochargersDiesel Engine Turbochargers• Variable Turbocharger
– Oil flow has three modes:• Hold maintains the vanes in a fixed position
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel Engine TurbochargersDiesel Engine Turbochargers• Variable Turbocharger
– Oil flow has three modes:• Release moves the vanes toward the open
position
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Figure 19-20 A variable vane turbocharger allows the boost to be controlled without the need of a wastegate.
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EXHAUST GASEXHAUST GASRECIRCULATIONRECIRCULATION
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Exhaust Gas RecirculationExhaust Gas Recirculation• The EGR system recycles exhaust gas
back into the intake stream to cool combustion
• Oxides of nitrogen (NOx) emissions are reduced
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Exhaust Gas RecirculationExhaust Gas Recirculation• The EGR System includes:
– Plumbing that carries exhaust gas from the turbocharger exhaust inlet to the intake ports
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Exhaust Gas RecirculationExhaust Gas Recirculation• The EGR System includes:
– EGR control valve– Stainless steel cooling element used to cool
the exhaust gases
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Exhaust Gas RecirculationExhaust Gas Recirculation• The EGR valve is PCM controlled and
often uses a DC stepper motor and worm gear to move the valve stem open
• Return spring force closes the valve
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Exhaust Gas RecirculationExhaust Gas Recirculation• EGR valve and sensor assembly is a
five-wire design
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Figure 19-21 A cutaway showing the exhaust cooler. The cooler the exhaust is, the more effective it is in controlling NOx emissions.
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DIESEL PARTICULATEDIESEL PARTICULATEMATTERMATTER
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel Particulate Matter Diesel Particulate Matter • Particulate Matter Standards
– Particulate matter (PM) is also called soot– Tiny particles of solid or semisolid material
in the atmosphere
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Diesel Particulate Matter Diesel Particulate Matter • Particulate Matter Standards
– Particulates are generally categorized as follows:
• Total suspended particulate (TSP)• PM10, PM2.5
?
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Figure 19-22 Relative size of particulate matter to a human hair.
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Diesel Particulate Matter Diesel Particulate Matter • Soot Categories
– Fine– Ultrafine
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DIESEL OXIDATIONDIESEL OXIDATIONCATALYSTCATALYST
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel Oxidation CatalystDiesel Oxidation Catalyst• Purpose and Function
– Used in all light-duty diesel engines since 2007
– Main function of the Diesel Oxidation Catalyst (DOC) is to start a regeneration event by converting the fuel-rich exhaust gases to heat
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Diesel Oxidation CatalystDiesel Oxidation Catalyst• Purpose and Function
– The DOC also reduces:• Carbon monoxide (CO)• Hydrocarbons (HC)
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Diesel Oxidation CatalystDiesel Oxidation Catalyst• Purpose and Function
– The DOC also reduces:• Odor-causing compounds such as aldehydes
and sulfur
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Figure 19-23 Chemical reaction within the DOC.
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DIESEL EXHAUSTDIESEL EXHAUSTPARTICULATE FILTERPARTICULATE FILTER
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Diesel Exhaust Particulate FilterDiesel Exhaust Particulate Filter• Purpose and Function
– Used in all light-duty diesel vehicles since 2007 to meet the exhaust emissions standards
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Figure 19-24 Aftertreatment of diesel exhaust is handled by the DOC and DPF.
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Diesel Exhaust Particulate FilterDiesel Exhaust Particulate Filter• Operation
– Soot particulates in the gas are trapped on the Diesel Exhaust Particulate Filter (DPF) channel walls
– Filter must be purged to remove soot particles (regeneration)
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Figure 19-25 The soot is trapped in the passages of the DPF. The exhaust has to flow through the sides of the trap and exit.
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Diesel Exhaust Particulate FilterDiesel Exhaust Particulate Filter• Exhaust Gas Temperature Settings
– Two exhaust gas temperature sensors are used to help the PCM control the DPF
• EGT sensor 1 and EGT sensor 2
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Figure 19-26 EGT 1 and EGT 2 are used by the PCM to help control after treatment.
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Diesel Exhaust Particulate FilterDiesel Exhaust Particulate Filter• DPF Differential Pressure Sensor
– Two pressure sample lines:• One is attached before the DPF
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Diesel Exhaust Particulate FilterDiesel Exhaust Particulate Filter• DPF Differential Pressure Sensor
– Two pressure sample lines:• The other is located after the DPF
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Diesel Exhaust Particulate FilterDiesel Exhaust Particulate Filter• DPF Differential Pressure Sensor
– The exact location varies by type of vehicle
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Diesel Exhaust Particulate FilterDiesel Exhaust Particulate Filter• Diesel Particulate Filter Regeneration
– Several factors can trigger the diesel PCM to perform regeneration, including:
• Distance since last DPF regeneration
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Diesel Exhaust Particulate FilterDiesel Exhaust Particulate Filter• Diesel Particulate Filter Regeneration
– Several factors can trigger the diesel PCM to perform regeneration, including:
• Fuel used since last DPF regeneration
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Diesel Exhaust Particulate FilterDiesel Exhaust Particulate Filter• Diesel Particulate Filter Regeneration
– Several factors can trigger the diesel PCM to perform regeneration, including:
• Engine run time since last DPF regeneration
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Diesel Exhaust Particulate FilterDiesel Exhaust Particulate Filter• Diesel Particulate Filter Regeneration
– Several factors can trigger the diesel PCM to perform regeneration, including:
• Exhaust differential pressure across the DPF
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Diesel Exhaust Particulate Filter Diesel Exhaust Particulate Filter • DPF Regeneration Process
– PCM controls that impact DPF regeneration include late post injections, engine speed, and adjusting fuel pressure
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Diesel Exhaust Particulate Filter Diesel Exhaust Particulate Filter • DPF Regeneration Process
– Late post injection pulses provide the engine with additional fuel to be oxidized in the DOC
?
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Diesel Exhaust Particulate Filter Diesel Exhaust Particulate Filter • DPF Regeneration Process
– The intake air valve acts as a restrictor that reduces air entry to the engine
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Diesel Exhaust Particulate Filter Diesel Exhaust Particulate Filter • DPF Regeneration Process
– The intake air heater may also be activated to warm intake air during regeneration
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Figure 19-27 Regeneration burns the soot and renews the DPF.
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Diesel Exhaust Particulate Filter Diesel Exhaust Particulate Filter • Types of DPF Regeneration
– Passive regeneration– Active regeneration
?
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Diesel Exhaust Particulate FilterDiesel Exhaust Particulate Filter• Ash Loading
– Ash is a noncombustible by-product from normal oil consumption
– Ash accumulation causes a restriction in the particulate filter
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Diesel Exhaust Particulate FilterDiesel Exhaust Particulate Filter• Ash Loading
– The DPF will need to be removed and cleaned or replaced
– Low ash content engine oil (API CJ-4) is required for vehicles with the DPF system
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SELECTIVE CATALYTICSELECTIVE CATALYTICREDUCTIONREDUCTION
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
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Selective Catalytic ReductionSelective Catalytic Reduction• Purpose and Function
– Method used to reduce NOx emissions– Selective Catalytic Reduction (SCR) system
uses a urea (nitrogen fertilizer)
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Selective Catalytic ReductionSelective Catalytic Reduction• Purpose and Function
– Urea is called diesel exhaust fluid (DEF) in North America and AdBlue in Europe
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Figure 19-30 Diesel exhaust fluid costs $3 to $4 a gallon and is housed in a separate container that holds from 5 to 10 gallons, or enough to last until the next scheduled oil change in most diesel vehicles that use SCR.
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Selective Catalytic ReductionSelective Catalytic Reduction• Purpose and Function
– Chemical reaction converts nitrogen oxides (NOx) into nitrogen (N2) and water (H2O)
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Selective Catalytic ReductionSelective Catalytic Reduction• Purpose and Function
– Urea storage tank needs to be refilled at each scheduled oil change or every 7,500 miles (12,000 km)
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Figure 19-31 Urea (diesel exhaust fluid) injection is used to reduce NOx exhaust emissions. It is injected after the diesel oxidation catalyst (DOC) and before the diesel particulate filter (DPF) on this 6.7 liter Ford diesel engine.
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Selective Catalytic ReductionSelective Catalytic Reduction• Advantages of SCR
– Potential higher engine power output for the same size engine
– Reduced NOx emissions up to 90%
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Selective Catalytic ReductionSelective Catalytic Reduction• Advantages of SCR
– Reduced HC and CO emissions up to 50%– Reduced particulate matter (PM) by 50%
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Selective Catalytic ReductionSelective Catalytic Reduction• Disadvantages of SCR
– Onboard storage tank required for the urea– Difficult to find local sources of urea
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Selective Catalytic ReductionSelective Catalytic Reduction• Disadvantages of SCR
– Increased costs to the vehicle owner due to having to refill the urea storage tank
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DIESEL EXHAUSTDIESEL EXHAUSTSMOKE DIAGNOSISSMOKE DIAGNOSIS
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Diesel Exhaust Smoke DiagnosisDiesel Exhaust Smoke Diagnosis• Black Smoke
– Caused by incomplete combustion– Items that should be checked include the
following:• Fuel specific gravity (API gravity)
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Diesel Exhaust Smoke DiagnosisDiesel Exhaust Smoke Diagnosis• Black Smoke
– Items that should be checked include the following:
• Injector balance test to locate faulty injectors using a scan tool
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Diesel Exhaust Smoke DiagnosisDiesel Exhaust Smoke Diagnosis• Black Smoke
– Items that should be checked include the following:
• Proper operation of the engine coolant temperature (ECT) sensor
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Diesel Exhaust Smoke DiagnosisDiesel Exhaust Smoke Diagnosis• Black Smoke
– Items that should be checked include the following:
• Proper operation of the fuel rail pressure (FRP) sensor
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Diesel Exhaust Smoke DiagnosisDiesel Exhaust Smoke Diagnosis• Black Smoke
– Items that should be checked include the following:
• Restrictions in the intake or turbocharger• Engine oil usage
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Diesel Exhaust Smoke DiagnosisDiesel Exhaust Smoke Diagnosis• White Smoke
– Occurs most often during cold engine starts– The most common causes of white exhaust
smoke include:• Inoperative glow plugs
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Diesel Exhaust Smoke DiagnosisDiesel Exhaust Smoke Diagnosis• White Smoke
– The most common causes of white exhaust smoke include:
• Low engine compression
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Diesel Exhaust Smoke DiagnosisDiesel Exhaust Smoke Diagnosis• White Smoke
– The most common causes of white exhaust smoke include:
• Incorrect injector spray pattern
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Diesel Exhaust Smoke DiagnosisDiesel Exhaust Smoke Diagnosis• White Smoke
– The most common causes of white exhaust smoke include:
• Coolant leak into the combustion chamber
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Diesel Exhaust Smoke DiagnosisDiesel Exhaust Smoke Diagnosis• Gray or Blue Smoke
– Blue exhaust smoke is usually due to oil consumption caused by worn piston rings, scored cylinder walls, or defective valve stem seals
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Diesel Exhaust Smoke DiagnosisDiesel Exhaust Smoke Diagnosis• Gray or Blue Smoke
– Gray or blue smoke can also be caused by a defective injector(s)
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DIESEL PERFORMANCEDIESEL PERFORMANCEDIAGNOSISDIAGNOSIS
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Diesel Performance DiagnosisDiesel Performance Diagnosis• Diesel engines can be diagnosed using
a scan tool in most cases• Common faults include:
– Hard starting
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Diesel Performance DiagnosisDiesel Performance Diagnosis• Common faults include:
– No start– Extended cranking – Low power
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Diesel Performance DiagnosisDiesel Performance Diagnosis• Using a scan tool, check the sensor
values in Chart 19-2 to help find the source of the problem
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Chart 19-2 The values can be obtained by using a scan tool and basic test equipment. Always follow the vehicle manufacturer’s recommended procedures.
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Chart 19-2 (continued) The values can be obtained by using a scan tool and basic test equipment. Always follow the vehicle manufacturer’s recommended procedures.
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Figure 19-32 A pressure gauge checking the fuel pressure from the lift pump on a Cummins 6.7 liter diesel.
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COMPRESSION COMPRESSION TESTINGTESTING
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Compression TestingCompression Testing• Used to determine the mechanical
condition of a diesel engine• Testing includes the following:
– Remove the glow plug (if equipped) or the injector
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Compression TestingCompression Testing• Testing includes the following:
– Use a diesel compression gauge• A diesel engine should produce at least
300 PSI (2,068 kPa) of compression pressure
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Compression TestingCompression Testing• Cylinders should be within 50 PSI (345
kPa) of each other
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Figure 19-33 A compression gauge that is designed for the higher compression rate of a diesel engine should be used when checking the compression.
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GLOW PLUG GLOW PLUG RESISTANCERESISTANCE
BALANCE TESTBALANCE TEST
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Glow Plug Resistance Balance TestGlow Plug Resistance Balance Test• To test for even cylinder balance using
glow plug resistance, perform the following on a warm engine– Unplug, measure, and record the resistance
of all glow plugs
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Glow Plug Resistance Balance TestGlow Plug Resistance Balance Test• To test for even cylinder balance using
glow plug resistance, perform the following on a warm engine– With the wires still removed from the glow
plugs, start the engine
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Glow Plug Resistance Balance TestGlow Plug Resistance Balance Test• To test for even cylinder balance using
glow plug resistance, perform the following on a warm engine– Allow the engine to run for several minutes
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Glow Plug Resistance Balance TestGlow Plug Resistance Balance Test• To test for even cylinder balance using
glow plug resistance, perform the following on a warm engine– Measure the plugs and record the
resistance of all glow plugs
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Glow Plug Resistance Balance TestGlow Plug Resistance Balance Test• To test for even cylinder balance using
glow plug resistance, perform the following on a warm engine– Another test is to measure exhaust
manifold temperature at each exhaust port using an infrared thermometer or a pyrometer
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INJECTOR POP TESTINGINJECTOR POP TESTING
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Injector Pop TestingInjector Pop Testing• To test for even cylinder balance using
glow plug resistance, perform the following on a warm engine– Pop tester - device used for checking a
diesel injector nozzle for proper spray pattern
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Injector Pop TestingInjector Pop Testing• To test for even cylinder balance using
glow plug resistance, perform the following on a warm engine– Spray pattern should be a hollow cone, but
can vary
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Injector Pop TestingInjector Pop Testing• To test for even cylinder balance using
glow plug resistance, perform the following on a warm engine– Test nozzle for leakage
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Injector Pop TestingInjector Pop Testing• To test for even cylinder balance using
glow plug resistance, perform the following on a warm engine– Cleaning, repairing, or replacing the
injector nozzle may be necessary
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Figure 19-34 A typical pop tester used to check the spray pattern of a diesel engine injector.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Figure 19-35 The letters on the side of this injector on a Cummins 6.7 liter diesel indicate the calibration number for the injector.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
DIESEL EMISSION DIESEL EMISSION TESTINGTESTING
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Diesel Emissions TestingDiesel Emissions Testing• Opacity Test
– Most common test– Opacity means the percentage of light that
is blocked by the exhaust smoke
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Diesel Emissions TestingDiesel Emissions Testing• Opacity Test
– Opacity means the percentage of light that is blocked by the exhaust smoke
• 0% opacity - exhaust has no visible smoke and does not block light from a beam projected through the exhaust smoke
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Diesel Emissions TestingDiesel Emissions Testing• Opacity Test
– Opacity means the percentage of light that is blocked by the exhaust smoke
• 100% opacity - exhaust is so dark that it completely blocks light from a beam projected through the exhaust smoke
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Diesel Emissions TestingDiesel Emissions Testing• Opacity Test
– Opacity means the percentage of light that is blocked by the exhaust smoke
• 50% opacity - exhaust blocks half of the light from a beam projected through the exhaust smoke
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Chart 19-3 An opacity test is sometimes used during a state emission test on diesel engines.
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Diesel Emissions TestingDiesel Emissions Testing• Snap Acceleration Test
– Vehicle is held stationary– Wheel chocks are in place
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Diesel Emissions TestingDiesel Emissions Testing• Snap Acceleration Test
– Brakes released– Engine rapidly accelerated to high idle with
transmission in neutral
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Diesel Emissions TestingDiesel Emissions Testing• Snap Acceleration Test
– Conducted a minimum of six times – Three most consistent measurements are
averaged for final score
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Diesel Emissions TestingDiesel Emissions Testing• Rolling Acceleration Test
– Manual transmission vehicles– Rapidly accelerated in low gear from an
idle speed to a maximum governed RPM
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Diesel Emissions TestingDiesel Emissions Testing• Stall Acceleration
– Automatic transmission vehicles held stationary
– Parking and service brakes applied
19 DIESEL ENGINE OPERATION AND DIAGNOSIS
Automotive Technology, Fourth EditionJames Halderman
© 2011 Pearson Education, Inc.All Rights Reserved
Diesel Emissions TestingDiesel Emissions Testing• Stall Acceleration
– Transmission in "drive"– Accelerator pressed and held momentarily