1999 AUDI A4 fuel cap

24-19


WARNING!
Fire hazard! DO NOT smoke or work near
heaters of have anything in the area that can
ignite fuel. The fuel system is pressurized.
Before loosening hose connections or opening
the test connection), place a cloth around the
connection.
Install intake manifold in reverse order. (Tightening
torque of bolts: 10 Nm) 15 -
Loosen indicated hose. This hose leads to
the suction side of turbocharger bank 1.
16 -
Loosen fuel return line from fuel rail
(catch escaping fuel with clean rag).
17 -
Loosen fuel supply line from fuel rail.
18 -
Loosen indicated hose at EVAP valve.
- Unbolt intake manifold from cylinder
heads and carefuly lift intake manifold
from cylinder heads.
Pa
ge 21 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1

24-33

Fuel pressure regulator and residual
fuel pressure, checking


Requirements

Fuel pump relay OK
Fuel pump OK
Fuel filter OK
Battery voltage at least 11 V

Note:
The fuel pressure regulator regulates the fuel
pressure according to intake manifold pressure.
This ensures that the drop in pressure at the
injectors remains the same throughout all engine
speed and engine load ranges.

WARNING!

Fire hazard! The fuel system is pressurized.
Before loosening hose connections or
opening the test connection (to measure fuel
pressure), place a cloth around the
connection. Then release pressure by
carefully pulling off the hose or cap.
Pa
ge 38 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1

24-43

Fuel injection volume, fuel injector
leakage and spray pattern of injectors,
checking


WARNING!

Fire hazard! The fuel system is pressurized.
Before loosening hose connections or
opening the test connection (to measure fuel
pressure), place a cloth around the
connection. Then release pressure by
carefully pulling off the hose or cap.

Test conditions

Fuel pressure OK; testing Page 24
-33
.
To reach the fuel rail, the following steps must be
performed on vehicles with manual transmission
(without secondary air injection). On vehicles
with automatic transmission (with secondary air
injection) are minor differences in the work
procedure.

Several hoses must now be disconnected: - Unscrew bolts on air duct at points indicated (arrows) and remove air
duct.
- Absolute cleanliness must be maintained.
Pa
ge 51 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1

24-46


WARNING!
Fire hazard! The fuel system is pressurized.
Before loosening hose connections or opening
the test connection, place a cloth around the
connection. Then release pressure by carefully
pulling off the hose or cap. 10 -
Briefly open screw connection on fuel rail
(supply hose) to release pressure. Use
clean cloth to catch any fuel that leaks
out. Then tighten screw connection again.
11 -
Unbolt fuel rail from intake manifold at the
points indicated (see arrows).
Tightening torque bolts: 10 Nm
Pa
ge 55 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1

24-48

Checking for leaks

- Bridge sockets 1 and 65 on the test box using
test leads from VAG1594 A connector test kit.
(This creates an Ground (GND) connection to
one side of the fuel pump relay coil.)

Note:
Once the socket are bridged the fuel pump runs
continuously, even if the engine is not running.
This is because the fuel pump relay receives its
positive voltage supply via the central electrics.
The negative voltage supply for the fuel pump
relay comes via the cable bridge on the test box.

WARNING!

Fire hazard. DO NOT smoke or work near
heaters or have anything in the area that can
ignite fuel!

- Check injectors fuel for leaks (visual check).
When fuel pump is running, only 1 or 2 drops
should escape per minute from each injector.

- If fuel loss is greater, switch off fuel pump
(remove bridge) and replace faulty injector
Page 24
-53
, also observe notes on Page 24
-
53
.
Pa
ge 57 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1

24-51

- Repeat test for fuel injectors from second bank
of cylinders.

- If measured values for all fuel injectors are
outside tolerance range (specification), check
fuel pressure Page 24
-33
.

Note:
When checking the injection quantity, also check
the spray pattern. The spray pattern should be
the same for all the injectors.
Installation of the fuel rail together with injectors
is performed in the reverse sequence. The
following points should be noted when installing:

Replace O-rings at all opened connections.
(When replacing the front O-ring, make sure
not to remove the plastic cap from the
injector head. The O-ring must be pulled off
over the plastic cap.)
Moisten O-rings with clean engine oil.
Pa
ge 61 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1