1999 AUDI A4 fuel

impulses from the engine control unit (rather than going out completely)
and become much brighter when receiving an impulse.
Pa
ge 49 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

24-42
If the diode test lamp does not flash:

- Connect test box VAG 1598/31 to wiring
harness for engine control unit. Do not connect
to the engine control unit itself. Page 24
-20
.

- Test for open circuit or short to B+ in wiring between engine control
module and contact 2 on harness connector for fuel injector being
tested.
Contact 2 on
connector for injector,
Cylinder No. Test box VAG 1598/31, socket
1 96
2 112
3 88
4 97
5 113
6 89
- Rectify short circuit or open circuit if necessary.
- If wiring is OK, install a new engine control module Page 24
-24
.
Pa
ge 50 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

- After completing test, use new hose clamps and make sure they are
installed properly.
Pa
ge 52 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

24-44


1 -
Detach Wastegate Bypass Regulator
Valve -N75 from fuel rail. The hoses must
remain connected.
2 -
Disconnect harness connector from EVAP
Canister Purge Regulator Valve -N80.
3 -
Disconnect harness connector from
Recirculating valve for turbocharger -
N249.
4 -
Open hose clamps shown in the
illustration and detach hoses from air
recirculating valve.
5 -
Open hose clamp on fuel pressure
regulator and detach hose.
6 -
Disconnect harness connectors from
injectors on cylinder banks 1 and 2.
Pa
ge 53 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

24-45


7 -
Open hose clamp and detach hose
(vacuum hose for applying vacuum to the
mechanical air recirculating (Bypass)
valves when required).
8 -
Open hose clamps shown in the
illustration and detach hoses. (The hoses
lead to the intake (suction) sides of the
turbochargers for cylinder banks 1 and 2).
9 -
Open hose clamp shown in the illustration
and detach hose. (The hose supplies fuel
vapor to the intake manifold).
Pa
ge 54 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

24-47

- Lift fuel rail off intake manifold together with fuel
injectors and support the fuel rail.

Note:

After lifting off the fuel rail, check to make sure
that the injectors are properly secured to the
fuel rail.
It is possible that some of the fuel injectors will
become detached from the fuel rail and remain
in the intake manifold when the fuel rail is
removed. If this happens, install the fuel
injectors back onto the fuel rail Page 24
-53
.

WARNING!
Make sure test box is inside of passenger compartment. - Connect test box VAG 1598/31 to wiring harness for engine control
unit. Do not connect to the engine control module itself Page 24
-20
.
Pa
ge 56 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