fuel pressure AUDI A8 1999 D2 / 1.G AEB Engine Motronic MFI And Ignition System

24-2


1 -
Heated Oxygen Sensor (HO2S) -G39- with
Oxygen Sensor (O2S) heater -Z19-
2 -
Engine Coolant Temperature (ECT) sensor
-G62-
4-pin connector
3 -
Harness connector for: Heated Oxygen Sensor (HO2S) -G39- and
Oxygen Sensor (O2S) heater -Z19- (4-pin,
brown) Oxygen Sensor (O2S) behind Three Way
Catalytic Converter (TWC) -G130- with
Oxygen Sensor (O2S) heater -Z29- (4-pin,
black) Engine speed (RPM) sensor -G28- (3-pin,
gray) Knock sensor (KS) 1 -G61 (3-pin, green)Knock sensor (KS) 2 -G66- (3-pin, blue)
4 -
Electronics box (E-box) with: Motronic Engine Control Module (ECM) -
J220- Barometric Pressure (BARO) sensor -F96-
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24-5

Safety precautions


WARNING!

Fire hazard! Do not smoke, work near heaters
or open flame, or have anything nearby that
could ignite fuel. The fuel system is under
pressure. Before opening, cover connections
with a rag, and open carefully to release
pressure. Be alert when working on or near
the engine and ignition wires. High secondary
ignition voltage can cause serious personal
injury and damage vehicle components.

DO NOT touch or disconnect ignition system
wires when the engine is running or being
cranked at starting RPM.
DO NOT operate starter if fuel injectors are
removed.

Be sure the ignition is switched OFF, when:
Disconnecting or connecting the battery,
ignition wires, or test equipment leads
Disconnecting fuel injection system wiring
Washing the engine or engine
compartment.
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24-8
Technical data

Engine code
AEB

Engine idle speed:
not adjustable, maintained by Idle Air Control (IAC) 820-900 RPM
Engine speed (RPM) upper limit:
actuated by switching off fuel injectors approx. 6500 RPM
Fuel system pressure at idle Vacuum hose for pressure regulator connected: approx. 3.5 bar
(50 psi)

Vacuum hose for pressure regulator disconnected: approx. 4.0 bar
(58 psi)

Residual fuel pressure after 10 minutes at least 2.5 bar
Fuel injectors Spray pattern: approx. the same for all fuel injectors

Resistance
1)
:
11-13 ohm
1) Engine at room temperature; with the engine at normal operating temperature the resistance increases by approx. 4-6
ohms.
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24-22
Evaluation of display group 32 Display group:
32


Display fields: 1
+ 2
Possible cause
Corrective action
O2S control
learning value:
-26.0 to -8.0 %
Engine oil dilution (when partial load learning value
is normal, display field 2)
- Change engine oil, or carry out extensive road
test and check again.


Fuel pressure too high- Check fuel pressure regulator Page 24
-93


Fuel injector leaking- Check fuel injectors Page 24
-87


Oxygen Sensor (O2S) heater malfunction- Check O2S heater Page 24
-27
O2S control
learning value:
8.0-26.0 %
Intake air leaks ("false air") or exhaust manifold
leaks (when partial load learning value is normal,
display field 2)
Repair Manual, 1.8 Liter 4
-Cyl. 5V Turbo
Engine Mechanical, Engine Code(s): AEB, ATW, Repair Group 26
- Check intake air system for leaks Page 24
-
97

- Check exhaust system for leaks:


Fuel pressure too low- Check fuel pressure regulator Page 24
-93


Oxygen Sensor (O2S) heater malfunction- Check O2S heater Page 24
-27
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24-91

Fuel injectors, checking for leakage


WARNING!

The fuel system is under pressure! Before
loosening hoses or opening the test
connection, cover the connection with a rag.
Only then, open carefully to slowly release
pressure.

Required special tools and test equipment

VW 1594 connector test kit
VAG 1630 digital potentiometer
VAG 1602 fuel analyzer

Checking

- Disconnect harness connector for Camshaft
Position (CMP) sensor -G40-.

- Disconnect vacuum hose from fuel pressure
regulator.

- Remove fuel rail together with fuel injectors.

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24-93

Fuel pressure regulator and residual
pressure, checking

The fuel pressure regulator controls the fuel
pressure depending on intake manifold
pressure.

Required special tools and test equipment

Pressure tester VAG 1318
Adapter 1318/11
Adapter 1318/12
Adapter 1318/13

Test requirements
Fuel pump delivery rate must be OK;
checking:

Repair Manual, Fuel Supply System, Repair
Group 20.


Checking
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WARNING!

The fuel system is under pressure! Before
loosening hoses or opening the test
connection, cover the connection with a rag.
Only then, open carefully to slowly release
pressure.
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24-94

- Open fuel filler cap briefly (release pressure).

- Cover the fuel supply line connection (arrow) to protect against fuel
spray.
- Slowly open connection and catch leaking fuel.

Note:
The valve on the pressure tester must be open (lever pointing in direction
of flow). - Connect pressure tester VAG 1318 to fuel rail using adapters VAG
1318/11, VAG 1318/12 and VAG 1318/13.
- Start engine and let run at idle.
- Measure fuel pressure.
Specified value: approx. 3.5 bar (50 psi)
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24-95


If residual pressure drops below 2.5 bar (36 psi): - Disconnect vacuum hose (arrow) for fuel pressure regulator.
Fuel pressure must increase to approximately 4.0 bar (58 psi)
- Reconnect vacuum hose.
- Switch ignition off.
- Check for residual fuel pressure by monitoring decrease in pressure on
gauge. Specified value:
After 10 minutes: at least 2.5 bar (36 psi)
- Start engine and let run at idle.
- After pressure has built up, at the same time:
- Switch ignition off.
- Close valve on pressure tester VAG 1318-lever in OFF position
(arrow).
- Monitor decrease in pressure on gauge.
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24-96
If residual pressure still drops below 2.5 bar (36
psi), possible malfunctions are:

Leaking connection between pressure tester
and fuel line
Leaking connection between fuel supply line
and fuel rail
Faulty check valve in fuel pump; removing and
installing:

Repair Manual, Fuel Supply System, Repair
Group 20

If residual pressure no longer drops below 2.5
bar (36 psi), the possible malfunctions are:

Leaking fuel pressure tester connections after
shut-off valve.
Faulty fuel pressure regulator
Leaking fuel injectors

Note:
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11/19/2002 htt
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yp
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