1996 AUDI A4 warning

24-1


Motronic Multiport Fuel
Injection (MFI) system,
servicing

Safety precautions


Observe following precautions if test and
measuring instruments are required during a
road test:

WARNING!

During a road test in an airbag equipped
vehicle, test equipment must always be
fastened to and operated from the rear seat
by a second technician.
When driving or riding in an airbag equipped
vehicle, NEVER hold the scan tool or other
test equipment in your hands or lap while in
motion. Objects between you and and the
airbag increase the risk of injury in an
accident.

To prevent injuries to persons and/or damage
to the fuel injection and ignition system, the
following must be noted:
Always switch off the ignition before
connecting or disconnecting injection or
ignition system wiring or tester cables.
Pa
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port Fuel In
jection
(MFI
) system, servicin
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11/22/2002 htt
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pair&id=AUDI.B5.FU04.24.1

24-6


Repair Manual, Fuel Supply System, Repair
Group 20, Components of EVAP system servicing
F - Electronic Power Control (EPC)
warning light
In instrument cluster (Significance of light
Page 24
-139
)
G - Leak Detection Pump (LDP) -V144
Below left rear wheelhousing liner
H - Oxygen Sensor (O2S) Behind Three
Way Catalytic Converter (TWC) -G130
with Heater for Lambda-probe 1 -Z29
This oxygen sensor is accessible from
below when vehicle is lifted
I - Oxygen Sensor (O2S) 2 Behind Three
Way Catalytic Converter (TWC) -G131
with Heater for Lambda-probe 2 -Z30 This oxygen sensor is accessible from
below when vehicle is lifted
Pa
ge 8 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
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11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
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e=re
pair&id=AUDI.B5.FU04.24.1

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
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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
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11/22/2002 htt
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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
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11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
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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
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11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
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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