A4 Sedan L4-1.8L Turbo (AEB) (1997)
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Start engine and let run at idle.
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Measure fuel pressure.
Specified value: approx. 3.5 bar (50 psi)
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Disconnect vacuum hose (arrow) for fuel pressure regulator.
Fuel pressure must increase to approximately 4.0 bar (58 psi)
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Reconnect vacuum hose.
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Switch ignition off.
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Check for residual fuel pressure by monitoring decrease in pressure on gauge. Specified value:
After 10 minutes: at least 2.5 bar (36 psi)
If residual pressure drops below 2.5 bar (36 psi):
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Start engine and let run at idle.
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After pressure has built up, at the same time:
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Switch ignition off.
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Close valve on pressure tester VAG 1318-lever in OFF position (arrow).
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Monitor decrease in pressure on gauge.
If residual pressure still drops below 2.5 bar (36 psi), possible malfunctions are:
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Leaking connection between pressure tester and fuel line
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Leaking connection between fuel supply line and fuel rail
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Faulty check valve in fuel pump; removing and installing:
If residual pressure no longer drops below 2.5 bar (36 psi), the possible malfunctions are:
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Leaking fuel pressure tester connections after shut-off valve.
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Faulty fuel pressure regulator
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Leaking fuel injectors
NOTE: When disconnecting the pressure tester, close the shut-off valve, disconnect adapter VAG 1328/12, then catch excess fuel in a container by
opening the shut-off valve.