1995 AUDI A4 fuel

24-32

System pressure, fuel pressure
regulator and residual pressure,
checking


Note:
Fuel pressure regulator regulates fuel pressure
according to intake manifold pressure. This
ensures that the pressure drop at the fuel
injectors remains the same for each speed and
load range of the engine.

Special Tools and Equipment

Test requirements:
Repair Manual, Fuel Supply System, Repair Group 20

VAG1318V.A.G 1318 with V.A.G 1318/11 adapter, V.A.G 1318/12 pressure
hose with connectors and V.A.G 1318/13 adapter Fuel Pump (FP) relay OK; checking Page 24
-52
.
Fuel Pump (FP) OK, checking: Fuel filter OK Battery voltage at least 12.7 V Vehicles with automatic transmission Selector lever in P or N.
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24-33

Checking system pressure

- Open fuel filler flap briefly (pressure release).

WARNING!
Fuel system is under pressure! Before opening system, place rags
around the connection point. Then release pressure by carefully
loosening connection. - Remove engine cover (arrows).

- Open threaded connection (arrow) and catch exiting fuel using a rag.
- Connect VAG1318 pressure gauge in supply line using adapters
1318/11, 1318/12 and 1318/13.
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24-34


- Open shut-off valve of pressure gauge. The lever points in the direction
of flow.
- Start engine and let run at idle.
- Measure fuel pressure.

Specification: about 3.5 bar positive pressure

- Disconnect vacuum hose at fuel pressure regulator.

Fuel pressure must rise to about 4.0 bar positive pressure.
- Switch ignition off.
- Check for proper seal and residual pressure by observing pressure
drop on pressure gauge.
After 10 minutes, there must be at least 2.5 bar positive pressure
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24-35
If residual pressure sinks below 2.5 bar positive
pressure:

- Start engine and let run at idle.

If pressure does not drop now:
If pressure drops again:
If pressure does not drop now: - Wait until pressure has dropped, and then switch off ignition.
Simultaneously close shut-off valve of VAG1318 pressure gauge (lever
perpendicular to direction of flow -arrow-).
- Observe pressure drop on pressure gauge.
- Test check-valve on Fuel Pump (FP).
- Open shut-off valve of pressure gauge. The lever points in the direction
of flow.
- Start engine and let run at idle.
- Wait until pressure has dropped, and then switch off ignition.
Simultaneously clamp return line (with blue marking) completely
closed.
- Replace fuel pressure regulator
Pa
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24-36
If pressure drops again:

- Check wire connections, O-rings at fuel
distributor and fuel injectors for proper seal.

- Check whether pressure gauge is properly
sealed.

Note:
Before disconnecting pressure gauge, release
pressure by opening shut-off valve. Hold a
container in front of connection for this.
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24-37


Fuel injectors, checking

Special Tools and Equipment

VAG1526A
VAG1527B
VAG1594A
VAG1598/31
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24-38

Checking internal resistance

- Remove engine cover (arrows).
- Disconnect connector at the fuel injector to be tested.

If specified value is not obtained:
If specified value is obtained: - Connect multimeter at valve for resistance measurement.

Specification: 12 to 13 (at room temperature)
- Replace fuel injector.
- Check voltage supply
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24-39

Checking voltage supply

Test requirements:

Fuse for fuel injectors OK

Electrical Wiring Diagrams, Troubleshooting &
Component Locations

Fuel Pump (FP) relay OK; checking Page 24
-52
.

- Disconnect harness connector at the fuel
injector to be tested.

If LED does not light up: - Connect VAG1527B voltage tester as follows:Harness connector
Terminal
Measure to
1 Engine Ground (GND)
- Switch ignition on.

LED must light up.
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jection s
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