fuel pressure AUDI A4 1995 B5 / 1.G AHA Engine Multiport Fuel Injection And Ignition System Workshop Manual

24-6


16 -
EVAP canister purge regulator valve -N80-
17 -
Engine Coolant Temperature (ECT) sensor
-G62-
4-pin connectorIn coolant pipe behind right cylinder head
(Bank 1)
18 -
Throttle valve control module -J338-
Includes:Throttle drive -G186-Angle sensor 1 for throttle drive -G187-Throttle Position (TP) sensor -G69-Closed Throttle Position (CTP) switch -
F60-
19 -
Intake Manifold Tuning (IMT) valve -N156-
(change-over valve)
20 -
Fuel pressure regulator
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24-9

Safety precautions


WARNING!

Fire hazard! Do not smoke, work near
heaters or open flame, or have anything
nearby that could ignite fuel. The fuel system
is under pressure. Before opening, cover
connections with a rag, and open carefully to
release pressure.
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 the airbag
increase the risk of injury in an accident.
During a test drive in an airbag-equipped
vehicle, test equipment must always be
fastened to and operated from the rear seat
by a second technician.
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24-13
Technical data

Engine code
AHA
Engine idle speed (with consumers
switched off)
not adjustable, maintained by Idle Air
Control (IAC) All-wheel drive vehicles 620-740 RPM
Front-wheel drive vehicles 740-860 RPM
Engine speed (RPM) upper limit
actuated by switching off fuel injectors approx. 6500 RPM
Fuel system pressure at idle With pressure regulator vacuum hose
connected approx. 3.2-3.8 bar
(46-55 psi)
With pressure regulator vacuum hose
disconnected approx. 3.8-4.2 bar
(55-61 psi)
Residual fuel pressure after 10 minutes Cold engine approx. 2.2 bar
(32 psi)
Warm engine approx. 3.0 bar
(44 psi)
Fuel injectors Spray pattern approx. the same for all fuel
injectors
Resistance 1)
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24-27
Evaluation of display group 32 Display group:
32


Display fields:
1-4
Possible malfunction cause
Corrective action
O2S control
learning value:
-25.0 to -10.0
%
Engine oil dilution (when part load learning value is
normal display fields 2 and 4)
- Change engine oil, or carry out extensive
road test and check again


Fuel pressure too high- Check fuel pressure regulator page 24
-
111



Fuel injector leaking- Check fuel injectors page 24
-102


Oxygen Sensor (O2S) heater malfunction- Check O2S heater page 24
-34
O2S control
learning value:
10.0 to 25.0 %
Intake air leaks ("false air") or exhaust manifold leaks
(when partial load learning value is normal display
fields 2 and 4)
- Check intake air system for leaks page 24
-126

- Check exhaust system for leaks Repair
Manual, 2.8 Liter V6 5V General, Engine,
Repair Group 26


Fuel pressure too low- Check fuel pressure regulator page 24
-
111



Oxygen Sensor (O2S) heater malfunction- Check O2S heater page 24
-34
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24-102

Fuel injectors, checking


WARNING!

Fire hazard! Do not smoke, work near heaters
or open flame, or have anything nearby that
could ignite fuel. The fuel system is under
pressure. Before opening, cover connections
with a rag, and open carefully to release
pressure.
Activating fuel injectors via output Diagnostic
Test Mode (DTM) page 01-51


Required special tools and test equipment

VAG1598/22 test box
Multimeter US1119 (Fluke 83 or equivalent)
VAG1527B LED voltage tester
VW1594 connector test kit
Wiring diagram

Test requirements

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24-106

Fuel injectors, checking for leakage


WARNING!

Fire hazard! Do not smoke, work near heaters
or open flame, or have anything nearby that
could ignite fuel. The fuel system is under
pressure. Before opening, cover connections
with a rag, and open carefully to release
pressure.

Required special tools and test equipment

VW1594 connector test kit
VAG1348/3A remote control connection
VAG1348/3-2 adapter cable
VAG1602 fuel analyzer

Test requirement
Fuel pressure regulator OK page 24
-111

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24-107

Checking

- Remove intake air hose between MAF sensor
and intake air noise muffler.

- Remove vacuum hose from Intake Manifold
Tuning (IMT) valve -N156- (change-over valve).

- Remove 5-pin connector from ignition coils, 2-
pin connector from valve for camshaft
adjustment -N208- (bank 2) and 2-pin connector
from camshaft position sensor -G163- (bank 1).

- Disconnect wiring harness from clips on fuel
rail.

- Disconnect fuel rail from intake manifold and remove fuel lines together
with injectors.
- Remove vacuum hose from fuel pressure regulator.
- Remove harness connectors from all injectors.
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24-109

- Operate remote VAG1348/3A 30 seconds.

Note:
The spray pattern must be the same for all
valves.
Once all three injectors in a single bank have
been checked:

- Place three measuring glasses on even surface
and check volume.

Specified volume per injector: 90-125 ml
If the measured volume of one or more injectors
is below or above the specified volume:

- Replace malfunctioning injector

- Repeat test to injectors in second bank of
cylinders.
If the measured volumes for all injectors are
under or over the specified volume:

- Check fuel pressure page 24
-111
.
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24-111

Fuel pressure, fuel pressure regulator
and residual fuel pressure, checking

The fuel pressure regulator controls the fuel
pressure depending on intake manifold
pressure.

WARNING!

Fire hazard! Do not smoke, work near heaters
or open flame, or have anything nearby that
could ignite fuel. The fuel system is under
pressure. Before opening, cover connections
with a rag, and open carefully to release
pressure.

Required special tools and test equipment

Pressure tester VAG1318
Adapter 1318/7
Adapter 1318/10
Adapter 1318/13

Test requirements
Fuel pump delivery rate OK; checking:
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24-112

Checking

Note:
Shut-off valve of pressure tester must be open (lever parallel to direction
of flow).
Note:
For the following test, do not let the engine run unnecessarily with the
vacuum hose removed, since the higher fuel pressure causes enrichment
of the fuel air mixture. The richer mixture could exceed the O2S control
limits and therefore cause a DTC to be stored.
Note:
If, during the following pressure test, fuel leaks from the vacuum
connection of the fuel pressure regulator, replace the fuel pressure
regulator. - Connect pressure tester VAG1318 between fuel supply line and fuel
rail using adapters 1318/7, 1318/10 and 1318/13.
- Remove vacuum line from fuel pressure regulator (to intake manifold)
and block line (using VW 3093).
- Switch off all electrical consumers (rear defrost, A/C etc.).
- Start engine and let idle.
- Measure fuel pressure.
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