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

Fire hazard! Do not smoke, work near
heaters or open flame, or have anything
nearby that could ignite fuel. 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 opening the
connection.
Pa
ge 2 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
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Technical data

Engine identification

APB
Idling speed
Not adjustable - controlled by Idle Air Control (IAT)

750 - 850 RPM
Engine speed (RPM) limitation
via fuel injector shut-off approx: 6800 RPM
Fuel pressure at idle speed Vacuum hose
connected
approx. 3.5 bar positive pressure

Vacuum hose
disconnected
approx. 4.0 bar positive pressure
Residual pressure after 10 minutes at least 2.5 bar positive pressure
Fuel Injectors Spray pattern Multi-hole nozzle (same on all injectors)

Injection qty. (30 secs.) 135 - 165 ml

Resistance
(room temperature)
1)
13.5 - 15.5
1) When the engine is at operating temperature the resistance is increased by approx. 4 - 6 .
Pa
ge 6 of 90 Motronic Multi
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jection
(MFI
) system, servicin
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12 -
Recirculating valve for turbocharger -
N249
13 -
Fuel pressure regulator
14 -
Camshaft Position (CMP) Sensor 2 -G163
Cylinder bank 2Previously identified as Camshaft Position
(CMP) Sensor 2 -G40
15 -
Secondary Air Injection (AIR) Pump Relay
-J299 Only on vehicles with automatic
transmission
16 -
Motronic Engine Control Module (ECM) -
J220
17 -
3-pin harness connector For Engine Speed (RPM) Sensor -G28grey
18 -
3-pin harness connector For Knock Sensor (KS) 2 -G66
19 -
Harness connector for Heated Oxygen
Sensor (HO2S) 2 -G108 and Oxygen
Sensor (O2S) Heater -Z28 4-pin black
Pa
ge 11 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
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24-10


20 -
Valve -2- for camshaft adjustment -N208
21 -
Throttle Valve Control Module -J338
With Throttle drive (power accelerator
actuation) -G186, Angle sensor -1- for
throttle drive (power accelerator actuation)
-G187 and Angle sensor -2- for throttle
drive (power accelerator actuation) -G188
22 -
Charge Air Pressure Sensor -G31 In rubber below before Throttle Valve
Control Module
23 -
Camshaft Position (CMP) Sensor 1 -G40 Cylinder bank 1Previously identified as Camshaft Position
(CMP) Sensor 1 -G163
24 -
Power output stage -N192 For ignition coils cylinder bank 2
25 -
Power output stage -N122 For ignition coils cylinder bank 1
Pa
ge 12 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
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Repair Manual, 2.7 Liter V6 5V BiTurbo Engine
Mechanical, Engine Code(s): APB, Repair Group 15
9 -
Disconnect harness connector at Throttle
Valve Control Module -J338.
10 -
Disconnect harness connector at Charge
Air Pressure Sensor -G31.
11 -
Remove indicated pressure hoses 12 -
Loosen indicated hose, this hose leads to
bypass valve.
13 -
Disconnect harness connector at Intake
Air Temperature (IAT) Sensor -G42.
14 -
Loosen indicated hose, (crankcase
ventilation hose).
Pa
ge 20 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
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24-27

Idle speed, checking


Test conditions

No leaks in exhaust system
Coolant temperature at least 80 C

Electrical consumers switched off (radiator
fan must not run during the check)
A/C switched off
Pressure gauge not connected
Selector lever in position P or N (vehicles
with automatic transmission)

Checking idle speed

Notes:
The idle speed cannot be adjusted.
The idle speed is tested during the basic setting
of the engine.
Pa
ge 31 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
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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
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11/22/2002 htt
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Testing system pressure

Note:
If fuel flows out at the vacuum connection on the fuel pressure regulator
during the following pressure test, fit a new fuel pressure regulator. - Connect pressure gauge VAG 1318 to supply pipe using adapters
1318/7, 1318/8 (pressure hose) and 1318/15.
- Disconnect vacuum hose between fuel pressure regulator and intake
manifold at fuel pressure regulator end; seal off end of hose.
- Start engine and run at idling speed.
- Measure fuel pressure.
Specified value: approx. 3.8...4.2 bar
- If fuel pressure does not match specification, install a new fuel
pressure regulator for test purposes and repeat pressure test.
- If fuel pressure still does not match specification, check fuel pump and
supply pipe for damage (e.g. pinching) and replace if necessary.
Pa
ge 39 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
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11/22/2002 htt
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- If pressure is higher than specification, check
return pipe for damage (e.g. pinching) and
renew if necessary.

Note:
During the following test, do not allow the engine
to run for too long with the vacuum hose
disconnected, otherwise the increased fuel
pressure will enrich the air/fuel mixture and may
cause the lambda control limits to be exceeded.
This would be stored as a fault in the fault
memory.

- Start the engine and run at idling speed.

- Switch off electrical consumers (air conditioner
etc.).

- Re-connect vacuum hose to fuel pressure
regulator and observe drop in pressure on
pressure gauge.
Pa
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port Fuel In
jection
(MFI
) system, servicin
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- When the vacuum hose is re-connected the fuel
pressure should drop by around 0.5 bar.

If the pressure does not change as specified,
carry out the following tests:


Check vacuum hose for cracks and other
damage.

Test vacuum hose for blockages at intake
manifold. To do this, disconnect hose at fuel
pressure regulator and blow into it.

- If there are no leaks and no blockages in the
vacuum hose, install new fuel pressure
regulator.

- Replace hose clamp that secures vacuum hose
to the fuel pressure regulator and make sure
that new clamp is properly installed.

Checking residual fuel pressure

- Residual pressure 10 minutes after switching off
engine (minimum pressure)

With engine cold: at least 2.2 bar
Pa
ge 41 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