Diesel Injector

Isi Kandungan

Bil Kandungan Muka Surat1. Penghargaan2. What Is Diesel Injector?3. How Do Diesel Fuel Injectors Work?4. Types of Diesel Fuel Injection5. Diesel Injection Pump Specifications6. Diesel Injection Pump Repair7. Injection Pump Problems8. How to Tell if a Diesel Pump is Good

What Is Diesel Injector?

When signalled by the engine control unit the fuel injector opens and sprays the

pressurised fuel into the engine. The duration that the injector is open (called the pulse width)

is proportional to the amount of fuel delivered. Depending on the system design, the timing

of when injector opens is either relative each individual cylinder (for a sequential fuel

injection system), or injectors for multiple cylinders may be signalled to open at the same

time (in a batch fire system).

Fuel injection is a system for admitting fuel into an internal combustion engine. It has

become the primary fuel delivery system used in automotive engines, having replaced

carburetors during the 1980s and 1990s. A variety of injection systems have existed since the

earliest usage of the internal combustion engine.

The primary difference between carburetors and fuel injection is that fuel injection

atomizes the fuel by forcibly pumping it through a small nozzle under high pressure, while a

carburetor relies on suction created by intake air accelerated through a Venturi tube to draw

the fuel into the airstream.

Modern fuel injection systems are designed specifically for the type of fuel being

used. Some systems are designed for multiple grades of fuel (using sensors to adapt the

tuning for the fuel currently used). Most fuel injection systems are for gasoline or diesel

applications.

How Do Diesel Fuel Injectors Work?

Mechanics of Diesel Fuel Injectors

Basic diesel fuel injectors contain a fuel supply line, an intake valve, an exhaust valve

and the fuel injection apparatus. Each cylinder is attached to its own fuel supply line, all of

which run from the fuel tank to the engine. Fuel is transferred through these fuel supply lines

to the fuel injector device attached to each cylinder. Along the way, the fuel passes through a

filter that removes residue and impurities.

When the diesel fuel reaches the injector device, it becomes highly pressurized. The

fuel injector is attached to a small pump, which forces air into the injector and pressurizes the

diesel fuel. The injector then sprays the diesel fuel through a small nozzle into the cylinder's

combustion chamber. The nozzle contains a series of small holes, which ensure even

distribution of the diesel fuel into the cylinder's combustion chamber.

An air intake valve sucks air into the chamber, which mixes with the vaporized diesel

fuel and intensifies the combustion. An exhaust valve removes the resulting emissions from

the combustion chamber, and a return fuel line removes any excess fuel from the combustion

chamber and returns it to the fuel tank.

Advancements in Diesel Fuel Injectors

Diesel fuel injectors have become increasingly sophisticated and efficient in recent

years. Modern diesel fuel injectors are regulated by computers, which monitor the amount of

air entering the engine and regulate the amount of diesel fuel that is sprayed into the

combustion chamber. Fuel injectors have also been modified slightly to accommodate the use

of biodiesel fuel, which is diesel fuel made from plant and animal oils rather than from

petroleum.

Biodiesels are not as powerful as petroleum-based diesel fuel, so more biodiesel fuel

is required to run an engine. Hence, diesel fuel injector pumps have become more powerful

and more closely integrated with the system's computer in order to ensure that the appropriate

amount of fuel is delivered to the combustion cylinder.

Types of Diesel Fuel Injection

Fuel injector pumps deliver an exact, measured amount of diesel to the injector under high

pressure and at a specified time. Diesel engines require the delivery of the fuel by the injector

directly into the cylinder or a prechamber serving the cylinder. This differs from gasoline

engines. Diesel engines may be classified by types of pumps as well as delivery method and

delivery location of the fuel by the injector.

Fuel Injector Requirements

A fine spray is necessary so that the diesel fuel vapor mixes quickly with air. This process is

enhanced by the proper placement of the injector in the cylinder head. This placement

requires precision in location and angle. Since the spray is consists of hot compressed air, the

injection must take place late in the compression cycle of the piston just before it reaches top

dead center. To achieve this function, the injector must deliver pressures as high as 29,000

psi.

Direct Injection Systems

Direct injection fuel systems (DI) introduce the fuel directly into the cylinder with improved

performance and lower compression ratios. This makes the use of DI possible in passenger

vehicles and light-duty trucks. Types of DI systems are the common rail system, radial

distributor injector system and the unit-pump system and unit-injector system. The common

rail system uses an independent pump and is not reliant upon engine speed. The distributor

injection systems are the most common on lighter vehicles and can be controlled

mechanically or electronically. Newer versions of the common rail system have reduced

emissions and are being utilized in passenger vehicles.

Indirect Injection

Indirect Injection Systems (IDI) operate at a higher compression ratio. This results in a more

rapid mixing of air and fuel. However, these systems suffer from greater heat loss than DI

systems. This is why IDI systems must have a high compression to reach the necessary

temperatures. This can result in lower fuel economy. The IDI systems are usually more

difficult to start and require glow plugs in the pre-chamber to provide necessary heat.

Turbocharging

Noise reduction, improved fuel economy and increased power are goals of diesel engine

manufacturers. A method to address these issues has been the use of turbochargers. One

configuration has been dual stage turbo charging. This employs two turbochargers that

operate during different ranges of engine performance. The added expense of a second

turbocharger has limited this technique to primarily high end diesel engines. Alloy pistons

and variable geometry turbochargers are being used in an attempt to address this issue.

Diesel Injection Pump Specifications

Diesel engines require a precisely metered amount of fuel, under high pressure and at

the right time, delivered to the injector. Unlike their gasoline-powered counterparts, diesel

engines require fuel injected indirectly into the cylinder---the job of a diesel injection pump.

Diesel injection pumps are not serviceable except by a few diesel experts. Mechanical diesel

injection pumps have begun to give way to alternative injection systems, such as common rail

diesel systems and electronic unit direct injection systems, which comply with international

emissions standards.

VE Type Injection Pump

VE stands for "Verteiler," German for "distributor" or "divider." The Verteiler

injection pump, used in Volkswagen diesels and other small diesel engines, has one fuel

metering plunger connected to a distributor that delivers the metered fuel to the correct

cylinder.

Inline Injection Pumps

Inline diesel injection pumps do without the distributor by having one fuel metering

plunger for each cylinder. The advantage of the VE pump lies in the fact that it has fewer

moving parts, but the moving parts of inline injection pumps are less complex and less

expensive to repair.

Common Rail Direct Fuel Injection

-pressure fuel pumps have given way to high-pressure alternatives, such as common

rail direct fuel injection systems, which can deliver pressures of up to 26,000 lbs. per square

inch. Both diesel and gasoline engines make use of common rail technology. Most

manufacturers under their own brand of this technology; for instance Fiat has the JTD, GM

the CDTi, Honda the i-CTDi and Ford the TDCi, to mention a few.

Diesel Injection Pump Repair

A diesel injection pump refers to a device used to pump or send fuel into the diesel

engine's cylinders. Diesel injection pumps can malfunction for numerous reasons; some basic

troubleshooting techniques usually resolve the problem.

Air in Fuel Lines

A loss of pressure results when air gets in the fuel lines of a diesel injection pump,

causing engine starting or stalling problems. Bleeding the fuel system of air and checking for

any leaks in the lines -- and replacing any lines as needed -- typically corrects the pump

problem.

Injector Clogging

Diesel injectors clog over time due to fuel sediment buildup in the nozzles. Perform

an injector overhaul every 100,000 to 150,000 miles, or as needed, to restore proper diesel

injection pump function.

Clogged Filter

A clogged fuel filter can keep a diesel injection pump from gaining access to the fuel

necessary to keep the engine running. The fuel filter should be regularly cleaned of any dirt

or sediment and replaced.

Injection Pump Problems

Injection pumps refer to devices used to pump fuel into diesel engine cylinders.

Injection pumps require precise timing, a high pressure environment and the synchronization

of numerous components. Issues involving any of these factors can lead to injection pump

problems.

Rotor Seizing

The injection pump rotor, or pump component that connects to the crankshaft in the

distributor section, can seize or lock up due to lack of pump lubrication. This lubrication

shortage often results from a clog in the pump. Under such circumstances, the pump and fuel

filters should be checked for clogs and lubrication should be added.

Ruptured Diaphragm

The diesel lift pump contains a diaphragm which fills with oil. A ruptured diaphragm

causes the pistons to vibrate and ultimately wear down. This results in fuel bypassing the

injection pump altogether, causing low or nonexistent fuel pressure. Replacing the diaphragm

and any worn pistons is necessary to restore proper injection pump function.

Excess Air

Air entering the fuel lines due to cracks, leaks or other entry points results in excess

air being pumped by the injection pump. This leads to fuel pressure loss, which can cause an

engine to stall or not start altogether.

How to Troubleshoot a Diesel Fuel Injection

With the complexity of today's diesel engines, the sheer number of things that can go

wrong in such a system is maddening. The diesel fuel injection system is the component of

the diesel engine that pumps the fuel into the engine. If this component is in some manner

malfunctioning, it can reduce the performance of your engine, cause unnecessary wear, or

even prevent your engine from starting. It is possible to troubleshoot a number of these

problems by yourself.

Instructions

1. Check for and clear any clogs in the distributor section of the fuel pump. These

clogs can cause the rotor to seize. These systems use the diesel fuel itself as a lubricant.

2. Check for air in the fuel lines if you are experiencing problems either with

starting the engine or you experience stalling. If air gets into the lines it results in a loss of

fuel pressure in the system, thus leading to problems such as the inability to start the engine

or stalling.

3. Check for corrosion on the circuit board responsible for the regulation of fuel

flow into the system. Check the bottom of your injection pump for the connections. If you

find significant corrosion, you may need to replace the unit. This problem results from the

nature of the technology itself, with the designs on which the injection system is based being

older than, and not meant for, the computer that controls it.

4. Check your fuel filter(s) for clogging. Change them if necessary. This type of

routine maintenance is generally performed every 100000 to 150000 miles.

5. Check for water in the fuel system. If you find water, you will need to replace

or repair the sylinator unit, which functions to remove water. Common symptoms of water in

the fuel system include stalling, poor performance, and not being able to start the engine.

6. Check for a rupture of the diesel lift pump diaphragm. Signs of a rupture

include wearing of the piston. Symptoms of such a rupture include a lack of fuel pressure or

low pressure.

7. Check the calibration of the injection unit. If you suspect the calibration is off,

recalibration is usually accomplished at a manufacturer's service center. This type of issue is

usually found in new systems.

How to Tell if a Diesel Pump is Good

In both diesel engines and in gasoline engines, the fuel is injected into the cylinders

by a fuel pump. The pump is obviously a very important part of the engine, since without it,

the cylinders would not receive any diesel fuel. If you recently purchased a diesel vehicle, or

if you just have a sneaking suspicion that the pump in your diesel is going bad, there are a

few ways that you can determine if the problem really is the pump. If you eliminate the

problems, your fuel pump is most likely fine.

Instructions

1.Listen for any moments of silence when your engine is running. Normally, you can

hear a study hum of the engine running. If this sound seems to stop intermittently, the

problem may be the diesel fuel pump. If your engine runs steadily, this indicates that fuel

pump is running well.

2.Try to start your engine. There are different sounds that an engine makes when

it is having certain problems. If the engine "cranks" -- sounds like it's trying to start, but does

not -- this indicates a problem with the fuel pump. If the engine starts normally, the fuel

pump is most likely good.

3. Focus on how the car runs when you are on the highway. If the vehicle

responds well to your gas and break pedal, your fuel pump is functioning well. If you notice

that the car slows down even when you haven't let off the gas, your fuel pump may need to be

replaced.

4. Examine the fuel pump while the engine is moving. Check to make sure it is

running smoothly and that there are no obvious signs of rust or mutilation.