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For the first time in theOCTAVIA, Skoda is offeringa modern turbodiesel engine
with direct injection.
This engine has an intelligentengine management systemto provide high output andlow fuel consumption!
... high output,
low fuel
consumption!
SP 16-1
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Technical Data 4
The TDI Engine 5
Highlights 8
System Architecture 12
Position of Components 14
System Overview 16
Sensors 18
Actuators 29
Fuel Metering Control 38
Commencement of Injection Control 40
Exhaust Gas Recirculation 42
Charge Pressure Control 44
Auxiliary Heater System 46
Glow Plug System 47
Emission Characteristics 48
Function Diagram 50
Self-Diagnosis 52
You can find information regarding inspection
and maintenance, setting and repair instructions
in the Workshop Manual
.
Contents
Service Service Service Service ServiceService
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Technical Data
Engine data:
Engine code: AGR
Type: 4-cylinder in-lineturbodiesel
Displacement: 1896 cm3
Bore: 79.5 mm
Stroke: 95.5 mm
Compression ratio: 19.5 : 1
Rated output: 66 kW (90 ch) at4000 rpm
Max. torque: 202 Nm at1900 rpm
Mixture formation: Direct injection with elec-tronically controlled distri-butor injection pump
Emission control: Exhaust gas recirculationand oxidation catalytic
convert
The 1.9-ltr. TDI engine achieves its maximumoutput of 66 kW (90 HP) at 4000 rpm.
The engine is characterized by a particularlygood torque curve. Maximum torque of 202 Nmis already available at 1900 rpm.These engine data reflect the excellent pulling
power of the engine.
SP 16-2
SP 16-3
P = OutputM = Torquen = Engine speed
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Special features of the
1.9-ltr. TDI engine
Electronic control
The quantity of fuel injected and the injection timingare controlled with the aid of the electronics to meetthe high demands in terms of fuel consumption andemissions.
This task is carried out by theE
lectronic D
iesel C
ontrol (
EDC
).It determines the quantity of fuel and the com-mencement of injection of the distributor injectionpump, controls charge pressure, exhaust gas recir-culation and glow period.
Bosch distributor injection pump VP 37 EDC with 800bar pump pressure. The distributor injection pump ispreset. The flange is pressed onto the drive shaft and
must not be removed.
Inlet port designed as swirl port. Sets the inducted airin a swirl motion, which ensures intensive swirling ofthe air in the combustion chamber.
Specially shaped piston bowl (main combustionchamber).
Injectors with two-stage fuel injection.
Charge pressure control.
Coolant pump installed in cylinder block.
Coolant thermostat installed in cylinder block.
Coolant preheated by electric auxiliary heater.
Alternator freewheeling.
Exhaust gas recirculation valve in intake manifold.
Plastic-coated injection pipes as a protection againstcorrosion.
Valve cover gasket vulcanized in place.
Oil pan with silicone sealant.
Replaceable oil filter designed as paper cartridge.
Vacuum pump driven by the camshaft.
Diesel direct injection system control unit
J248
The TDI Engine
SP 16-4
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Crankshaft
toothed belt pulley
The TDI Engine
The toothed belt drives the Camshaft Distributor injection pump Coolant pump
The required belt arc is achieved by two guide pul-leys, the tension by the semi-automatic toothed belttensioning pulley.
Brief description of mechanical components of the TDI
Setting distributor injection pump and toothed belt
Camshaft positionThe correct position is fixed by a new settinggauge. The exact middle position should bedetermined with feeler gauges.The exact camshaft position is of majorimportance for precise timing when fitting on thetoothed belt.
Injection pump gearThe position of the injection pump is fixed withthe locking drift. The injection pump gear is splitin two. A precision adjustment can be made by
slackening the 3 bolts - arrows -.
The exact procedure is described in the Workshop Manual
for the 1.9-ltr. turbodiesel engine
Camshaft gear
Injection
pump gearCoolant pump
Guide pulley
Semi-
automatic
tensioning
pulley
Locking drift
MP1-301
SP 16-5
SP 16-6
SP 16-7
Note:On no account slacken the nut for the hub of theinjection pump.If this is done, the basic setting of the injectionpump will be altered and cannot be correctly setagain with workshop tools.
Toothed belt settingAppropriate markings are provided for setting the
timing (crankshaft, camshaft, injection pump posi-tion).
Crankshaft positionMarking - top dead centre of cylinder 1 - is visibleon the flywheel through the inspection hole of thegearbox.
Note:When carrying service or repair work on the too-thed belt with the engine removed, align the mar-king on the ribbed V-belt pulley of the crankshaftwith the marking on the toothed belt cover.
Guide pulley
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The charge air cooler
The charge air cooler cools the inducted air before itenters the intake manifold. The charge air cooler isinstalled between the bumper and right wing and isforce-cooled by the airstream.
Why is the charge air cooler required?The turbocharger of the TDI engine heats the induc-ted air, which results in a loss of power of theengine.This loss of power is avoided by cooling the inductedair in the charge air cooler. The density of the airrises as the air temperature drops. The cylinders are
filled with colder and denser air which is richer inoxygen, and this in turn results in a further boost inengine output.
The cylinder head gasket is made of metal, which is why it is resistant to hig-her temperatures and pressures.The gasket can also be used in other engines of the 1.9-ltr. diesel enginerange.
SP 16-8
SP 16-9
Cylinder head gasket
Note:Take into account the differencein thickness.
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Injection nozzles
Stroke 1 +
Stroke 2
Stroke 2
Stroke 1
Spring 1
Spring 2
Nozzle needle
Two-spring nozzle holder
A gentle rise in pressure in the combustion chamber is required for minimisingcombustion noises and reducing the mechanical stresses. In addition, the fuelshould be injected not suddenly, but continuously over a lengthy period.
A two-spring nozzle holder has been developed for the 1.9-ltr. TDI engine withthe aim of achieving soft combustion. This nozzle holder injects the fuel in twostages.
Highlights
Function1st (prestroke)The nozzle holder contains two springs of different thickness. These are matchedto each other in such a way that the nozzle needle is raised only against the forceof spring 1 at the commencement of injection. As a result of the gap produced bystroke 1, only a small quantity of fuel is pre-injected at a low pressure
(p = 190 bar).This results in a gentle rise in the combustion pressure and creates the conditionsnecessary for igniting the main quantity of fuel.
2nd stage (total stroke)The injection pump constantly supplies more fuel. This results in a pressure rise inthe injection nozzle because the quantity of fuel supplied by the pump is not able toflow off through the small gap. As a result of this pressure rise, the force of spring 2is overcome and the nozzle needle raised by stroke 2 to the total stroke. As aresult of the enlarged gap, main injection occurs with the remaining quantity of fuelat a higher injection pressure (p = 300 bar).
SP 16-10
Nozzle holder
Prestroke Total stroke
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Magnetic coil
Thrust pin
Needle lift sender G80
The injection nozzle of the 3rd cylinder is equipped with a needle lift sender G80 for
detecting the commencement of injection.The sender monitors the actual moment of opening of the injection nozzle and thesignal is passed to the EDC control unit.The electronic control unit compares the incoming signal with the map for the com-mencement of injection and analyses the difference
.
Function
The needle lift sender G80 consists of amagnetic coil which is supplied with a con-stant current by the control unit. This cur-rent creates the magnetic field in the coil.
A thrust pin is located in the inside of themagnetic coil, as an extension of thenozzle needle. The movement of the thrustpin causes a change in the induced voltage
in the magnetic coil.
The moment of induction of the voltage inthe coil is compared by the control unit withthe top dead centre signal.The actual commencement of injection iscalculated from this difference. Followingthis, the "actual" value for the commence-ment of injection is compared with the "set"value, and commencement of injection iscorrected accordingly if differences exist.
Substitute function
If the needle lift sender fails, an emergencyrunning programme is activated. The com-mencement of injection is controlled withthis programme on the basis of a storedinjection map.In addition, the quantity of fuel injected isreduced.
SP 16-11
Nozzle holder
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Return-flow restrictor
Highlights
The return-flow restrictor is located in the deliveryvalve of the injection pump which controls the flowin the injection pipe to the pump. The purpose of thereturn-flow restrictor is to prevent fuel dripping outsubsequently at the injection nozzle and the forma-tion of vapour bubbles in the injection pipe.
Valve plate
Compression
spring
Restrictor drilling
Return flow
During the return flow the force ofthe compression spring acts on thevalve plate and shuts off the mainpassage. The fuel flows onlythrough the restrictor drilling. Thiscushions any pressure wave whichmay exist.
SP 16-13
Valve plate
Compression
spring
SP 16-14
Fuel delivery
During fuel delivery the valve plate islifted off by the fuel pressure and therestrictor drilling is inoperative. Thefuel flows through the main passage.
SP 16-12
Delivery valve
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Vacuum pump
The vacuum pump which is required additionally on a die-
sel engine for producing vacuum is driven directly by thecamshaft. The vacuum pump consists of a rotor and avane. The vane is made of plastic and is able to move on itsmountings.
Expansion of space
During a rotary movement of the rotor, the vane is pushedto the outside and the space is expanded. The space is fil-led with air, as a result of which a vacuum is produced atthe air inlet. The vacuum which is produced in the pump is
used by the brake servo unit and the EGR valve.
Vane
Rotor
Air inlet
(Vacuum connection
)
SP 16-16
Contraction of space
As the rotor and the vane continue to rotate, the space
produced again contracts. As a result of this, the inductedair is compressed and blown off through the air outlet tothe cylinder head. At the same time, a space is producedagain at the top.
Air outlet
VaneRotor
SP 16-17
SP 16-15
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System Architecture
The 1.9-ltr. TDI engine is equipped with an electronic engine control unit. All the control
systems of the engine are combined in the control unit.As a result of the electronic injected quantity control, it is possible to correct the quantity offuel injected in line with the air pressure, the air temperature, the coolant temperature andthe fuel temperature. In the past, using mechanical control systems, it was not possible toallow for these parameters.Use of the electronic control unit makes it possible to achieve demanding targets such asreducing fuel consumption and pollutant emissions while at the same time ensuring a highdegree of accuracy over long periods. At the same time, the system is able to react morerapidly to stresses which may occur at higher engine outputs.
N108
N109N146
G70G71 + G72
N18
AGR
G62
G28
G81 G149
N75 G80
Q6
VP
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Servicing of the engine is greatly simpli-fied and the number of operations invol-ved at an inspection is reduced as aresult of eliminating the need to set theinjection pump.
Any faults which occur can be rapidlydetected and easily rectified as a resultof the complete self-diagnosis system.
Control functions
Injected quantity control Calculating the quantity of fuel to be injected from
performance curves Start quantity control Fuel shut-off on overrun Limiting quantity injected if black exhaust is produ-
ced Controlling idling speed and limit speed of engine Controlling quantity injected for enhancing smooth
running
Injection advance Basic setting of commencement of injection accor-
ding to injection maps Correction in warming-up phase
Controlling the moment of injection when enginestarted
EGR exhaust gas recirculation Map-controlled
Charge pressure limit Map control of charge pressure Controlled in line with operating state
Auxiliary heater for coolant Map control of heating
Glow period Map monitoring of glow period After-glowing
Self-diagnosis Monitoring of sensors and actuators Fault memory Basic setting Diagnosis of actuators Emergency functions Reading results of measurements with fault reader
V.A.G 1551 or vehicle system tester V.A.G 1552.
SP 16-18
Note:You will find an explanation of the abbre-viated designations of the components inthe chapters on sensors and actuators.
J248
J366
T16
K29
F/F47 F36 G79
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J248
G80
N108N109
Q6
G71 + G72
AGR
N18
Position of Components
EGR EGR valve
G71 Intake manifold pressure sender
G72 Intake manifold temperature sender
G80 Needle lift sender
J248 EDC control unit
N18 EGR valve
N108 Commencement of injection valve
N109 Fuel cut-off valve
Q6 Glow plugs (engine)
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N75
J360J359
G70
Q7
G28 G62
G28 Engine speed sender
G62 Coolant temperature sender
G70 Air mass meter
J359 Low heating output relay
J360 High heating output relay
N75 Charge pressure control solenoid valve
Q7 Heating elements (coolant)
SP 16-19
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System Overview
The diesel direct injection system control unit J248 makes use of maps and characteristic curves in
order to ensure that the engine is operating optimally in terms of torque development, fuel con-sumption and emission characteristics in every operating situation.
System overview of electronic control of the TDI
Needle lift sender G80
Engine speed sender G28
Coolant temperature sender G62
Air mass meter G70
Intake manifold temperature sender G72
+ Intake manifold pressure sender G71
Brake light/brake pedal switch F/F47
Clutch pedal switch F36
Accelerator pedal position sender G79
+ Idling switch F60
+ Kickdown switch F8
Modulating piston movement sender G149
Fuel temperature sender G81
Additional signals
Sensors
Air conditioning
Terminal DF
DURC
HFLUSS
074906
461
FLOW
7 .18221.01GER
MANY
PIERBUR
G>PBT
-GF/M
40
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Glow plugs (engine) Q6
Glow plug relay J52
Heating element (coolant) Q7
Low heating capacity relay J359
Heating elements (coolant) Q7
High heating capacity relay J360
EGR valve N18
Charge pressure control solenoidvalve N75
Glow period warning lamp
K29
Commencement of injection
valve N108
Additional signals
Actuators
Fuel cut-off valve N109
Engine speed signal
Fuel consumption signal
Air conditioning
Diesel direct injection sy-
stem control unit J248
with altitude sender F96
Diagnostic connection
Quantity adjuster N146
SSP 16-20
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Sensors
Shaft
Potentiometer
Spiral spring
Accelerator pedal position senderG79
The determining factor for calculating the requiredquantity of fuel to be injected is the position of theaccelerator pedal - the driver input. This is detectedby a sender. The accelerator pedal position senderG79 is a potentiometer which is installed in thepedal mounting.It is operated by means of a short cable. The poten-tiometer passes the respective angle of rotation tothe electronic control unit.A spiral spring in the sender housing produces arestoring force which provides the driver with theimpression that he is operating a mechanical acce-
lerator pedal.In addition to the potentiometer, the sender alsoaccommodates the idling switch F60 and the kick-down switch F8.
Analysis of signalThe electronic control unit calculates the quantity offuel to be injected and the commencement of injec-tion from the signal supplied by the sender. In addi-tion, these signals are used for controlling thecharge pressure and for operating the exhaust gas
recirculation.
Substitute functionIf the sender is faulty, the engine runs at a fastidling speed of about 1300 rpm.This therefore enables the customer to drive to thenearest workshop. The accelerator pedal positionsender G79 does not operate in such a case.
Self-diagnosisThe fact that the sender signal is not plausible is
stored in the electronic control unit. This signal canbe checked in function "08", Reading measuredvalue block, display group "002". The figure for theaccelerator pedal position appears in the secondfield of the display as a %.
SP 16-21
SP 16-22
6
12 8
G79F60 8/F
24 11 23
248J
4 5 1 2 3
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Note:If, in addition, no signal is supplied by theneedle lift sender, the engine stops.
Engine speed sender G28
The engine speed is one of the most important
parameters for calculating the quantity of fuel to beinjected and the commencement of injection.The inductive sender for engine speed G28 moni-tors the angle position of the crankshaft. The sen-der rotor (a disc with four recesses) is mounted onthe crankshaft. The correct position is fixed by adowel pin. The distance between two successivepulses is measured in the electronic control unit.The momentary value of the position of the cranks-haft is calculated by analysing the four pulses.
SP 16-23
Analysis of signalThe signal is used for calculating the quantity offuel to be injected and the commencement of injec-tion. The signal supplied by the engine speed sen-der is analysed for performing the functions ofexhaust gas recirculation, preheating of the glowplug and the signal for the glow period warninglamp.
Substitute functionIf the engine speed sender develops a fault, theelectronic control unit switches over to the emer-gency mode.
The signal supplied by the needle lift sender G80 isused as a substitute signal. The commencement ofinjection is controlled according to the injectionmaps while charge pressure and quantity of fuelinjected are reduced. The idling speed monitor, thefuel shut-off on overrun and the air conditioning areswitched off, as a result of which engine speed isreduced slightly during brake applications. All in all,this fault is noticeable from an increase in idlingspeed.
SP 16-24
69 67
248J
1 2
G28
71
3
Self-diagnosisTwo possible causes of faults are stored in electro-nic control unit:
- Signal not plausible- No signal
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FLOW
7.18221.01
GERMANY
PIERB
URG>P
BT-GF/M40PBT-GF/M40PB
T-GF/M40