AUDI A4 1998 B5 / 1.G APB Engine Motronic Multiport Fuel Injection System Servising Repair Manual

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.
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- After completing test, use new hose clamps and make sure they are
installed properly.
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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.
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port Fuel In
jection
(MFI
) system, servicin
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11/22/2002 htt
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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).
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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

24-46


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
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port Fuel In
jection
(MFI
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11/22/2002 htt
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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
.
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jection
(MFI
) system, servicin
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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
.
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jection
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Checking injection quantity

- Place fuel injector which is to be tested into measuring glass from
injection quantity tester VAG1602.
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jection
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24-49


WARNING!
Make sure test box is inside of passenger compartment.
The fuel pump should run. - Connect one fuel injector terminal to engine Ground (GND) using test
cable and crocodile clamp from VAG1594 connector test kit.
- Connect second fuel injector terminal to B+ using remote control
VAG1348/3 A, adapter cable VAG1348/3-2 and auxiliary cable.
- 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.)
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jection
(MFI
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24-50

- Activate remote control VAG1348/3 A for 30
seconds.

- When all three fuel injectors from the first bank
of cylinders have been activated, place the three
measuring glasses on a level surface.

Specified value for each fuel injector: 135 ... 165
ml

- If measured value for one or more of fuel
injectors is outside tolerance range, switch off
fuel pump (switch ignition off) and replace faulty
fuel injector Page 24
-53
, also observe notes
on Page 24
-53
.
Pa
ge 60 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