A6 Sedan V6-2.8L (AHA) (1998)
If the specified value is exceeded:
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Check return line for damage (e.g. pinch locations); replace if necessary.
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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:
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Check vacuum line for leaks (cracks, damage).
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Check vacuum line at intake hose for obstruction; remove hose at fuel pressure regulator and blow into it.
If there is no leak and vacuum connection has no obstruction:
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Replace fuel pressure regulator.
Checking residual pressure
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Check residual pressure 10 minutes after shutting off engine.
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Cold engine (min.): approx. 2.2 bar (31.9 psi)
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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:
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Start engine and, after fuel pressure has increased, switch ignition off.
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Close shut off valve on VAG 1318 pressure tester.
If the residual pressure does not drop, the following malfunctions are possible.
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Connections between pressure gauge and fuel lines leaking
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Pre-feed line on fuel reservoir leaking
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Check valve in the electric fuel pump malfunctioning
If the residual pressure drops, the following malfunctions are possible:
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Malfunctioning fuel pressure regulator
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Injectors leaking
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Connections for the pressure gauge leaking behind shut-off valve
NOTE: To remove the pressure gauge, close the shut-off valve, loosen the connection on the VAG 1318/7 adapter and drain excess fuel by opening the
shut-off valve into collector container.