1999 AUDI A8 fuel

24-43

Fuel injectors, removing and installing


- Remove engine cover (arrows).
- Remove intake air hose between Mass Air Flow (MAF) sensor and
intake air elbow.
- Remove all harness connectors to injectors.
- Disconnect vacuum hose from fuel pressure regulator.
- Expose wires at fuel distributor.

WARNING!
Fuel system is under pressure! Place a cloth around the connection
point before opening system. Then release pressure by carefully
loosening connection point. - Unscrew fuel distributor from intake manifold (arrows) .
- Remove fuel distributor with injectors from intake manifold
simultaneously upward and set aside in rear of engine compartment on
a clean cloth.
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24-44

- Disengage retaining clip and remove fuel
injector.

Note:
Fuel lines must be disconnected before replacing
fuel distributor.
Installation is reverse of removal, noting the
following:

Remove O-rings at all opened connections.
(Never remove plastic cap from valve head
to replace front O-ring - pry O-ring off over
plastic cap).
Lightly lubricate O-rings with clean engine
oil.
Make sure fuel injectors are in place and
seated correctly
Check clip for unobstructed fitting.
Place fuel rail with secured fuel injectors
onto intake manifold, and apply uniform
pressure to press it in.

Tightening torque
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Component

Nm
Fuel distributor at intake manifold 10
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24-45


Injection quantity, proper seal and spray
pattern of fuel injectors, checking

Special Tools and Equipment

VAG1348/3A with VAG1348/3-2
VAG1594A
VAG1598/31
VAG1602
VAS5051 with VAG5051/1
- or
VAG1551 with VAG1551/3B
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24-46

Test requirement:

Fuel pressure OK, checking Page 24
-30
.

Test sequence

- Remove fuel distributor including fuel injectors
from intake manifold Page 24
-43
. Fuel lines
remain connected.

- Connect VAG1598/31 test box at wiring harness
to ECM, do not connect ECM Page 24
-17
.

- Bridge terminals 1 and 65 at test box using
adapter cables from VAG1594A connector test
kit (this step supplies Ground -GND- to one side
of relay coil for Fuel Pump -FP- relay).

Note:
Fuel Pump (FP) relay is supplied with B+ via the
central electric (terminal 30). Fuel Pump (FP)
relay receives minus via the cable bridge in test
box. The Fuel Pump (FP) is now running
constantly.
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24-47

Checking Proper Seal

- Check proper seal of fuel injectors (visual
inspection). With Fuel Pump (FP) running, only 1
to 2 drops per minute may drip out per injector.

- If fuel loss is greater, stop Fuel Pump (FP) from
running (disconnect cable bridge) and replace
faulty fuel injector Page 24
-43
.

Checking Injection Quantity

- Insert fuel injector to be tested in a measuring glass from VAG1602
injection quantity test device.

- Connect one terminal of fuel injector to engine Ground (GND) using an
adapter cable and an alligator clip from VAG1594A connector test kit.
- Connect the second terminal of fuel injector to B+ using VAG1348/3A
remote control, VAG1348/3-2 adapter cable and assisting cable.
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24-48

- Bridge terminals 1 and 65 at test box using wires
from VAG1594A adapter test kit.


Fuel Pump (FP) must run.

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

- After all three fuel injectors of one cylinder row
have been activated, place measuring glasses
on an even surface.

Specified value for each fuel injector: 90 to
125 ml.

- If measured value of one or more fuel injectors
is outside of specified range, switch Fuel Pump
(FP) off (disconnect cable bridge) and replace
faulty fuel injector Page 24
-43
.

- Repeat test at fuel injectors of second cylinder
row.

- If the measured values of all fuel injectors are
outside the specified range, check fuel pressure
Page 24
-30
.

Note:
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Also check spray pattern when checking injection
quantity. Spray pattern must be the same for all
injectors

- Install fuel injectors together with fuel distributor
Page 24
-44
.
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