AUDI A6 1995 C5 / 2.G AHA Engine Multiport Fuel Injection And Ignition System Workshop Manual

- Slide injectors (vertically) into position in fuel rail
and secure injectors with retaining clips.

- Place fuel rail together with secured injectors on
manifold and press fuel rail and secured
injectors in evenly.
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Fuel pressure, fuel pressure regulator
and residual fuel pressure, checking

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

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.

Required special tools and test equipment

Pressure tester VAG1318
Adapter 1318/7
Adapter 1318/10
Adapter 1318/13

Test requirements
Fuel pump delivery rate OK; checking:
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Repair Manual, Fuel Supply System, Repair
Group 20.

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Checking

Note:
Shut-off valve of pressure tester must be open (lever parallel to direction
of flow).
Note:
For the following test, do not let the engine run unnecessarily with the
vacuum hose removed, since the higher fuel pressure causes enrichment
of the fuel air mixture. The richer mixture could exceed the O2S control
limits and therefore cause a DTC to be stored.
Note:
If, during the following pressure test, fuel leaks from the vacuum
connection of the fuel pressure regulator, replace the fuel pressure
regulator. - Connect pressure tester VAG1318 between fuel supply line and fuel
rail using adapters 1318/7, 1318/10 and 1318/13.
- Remove vacuum line from fuel pressure regulator (to intake manifold)
and block line (using VW 3093).
- Switch off all electrical consumers (rear defrost, A/C etc.).
- Start engine and let idle.
- Measure fuel pressure.
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Specified value: approx. 3.8-4.2 bar (55.1-60.9 psi)
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If the specified value is not attained:

- Replace fuel pressure regulator and repeat
pressure test.
If the specified value is still not obtained:

- Check fuel pump or supply line for damage (e.g.
pinched locations); replace if necessary.
If the specified value is exceeded:

- Check return line for damage (e.g. pinch
locations); replace if necessary.

- Install vacuum hose on fuel pressure regulator
and check for pressure drop on gauge.

Specification: when vacuum hose is installed,
fuel pressure must drop by about 0.5 bar (7 psi).
If pressure does not change, the following tests
should be conducted:

- Check vacuum line for leaks (cracks,
damage).

-
Check vacuum line at intake hose for
obstruction; remove hose at fuel pressure
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regulator and blow into it.
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If there is no leak and vacuum connection has no
obstruction:

- Replace fuel pressure regulator.

Checking residual pressure

- Check residual pressure 10 minutes after
shutting off engine.


Cold engine (min.): approx. 2.2 bar (31.9
psi)

Warm engine (min.): approx. 3.0 bar (43.5
psi)

Note:
The higher pressure with a warm engine, caused
by fuel expansion, is normal.
If the specified value is not attained:

- Start engine and, after fuel pressure has
increased, switch ignition off.

- Close shut off valve on VAG1318 pressure
tester.
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If the residual pressure drops (is lower than
spec.) again, the following malfunctions are
possible.

Connections for the pressure gauge and fuel
lines leaking
Pre-feed line on fuel reservoir leaking
Check valve in the electric fuel pump
malfunctioning

Repair Manual, Fuel Supply System, Repair
Group 20, Checking fuel pump check valve

If retaining pressure does not drop, the following
malfunctions are possible:

Malfunctioning fuel pressure regulator
Injectors leaking
Connections for the pressure gauge leaking
behind shut-off valve

Note:
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To remove the pressure gauge, close the shut-off
valve, loosen the connection on the VAG1318/12
adapter and drain excess fuel by opening the
shut-off valve into collector container.
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