1999 AUDI A8 fuel pressure

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.
Pa
ge 130 of 135 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.1

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:
Pa
ge 131 of 135 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.1

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.
Pa
ge 132 of 135 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/19/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU02.24.1