2000 AUDI A8 AHA Engine Multiport Fuel Injection And Ignition System Workshop Manual

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.
Pa
ge 9 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

24-10

WARNING!

Be alert when working on or near the engine
and ignition wires. High secondary ignition
voltage can cause serious personal injury
and damage vehicle components.

DO NOT touch or disconnect ignition system
wires when the engine is running or being
cranked at starting RPM.
DO NOT operate the starter if fuel injectors
are removed.

Be sure the ignition is switched OFF, when:
Disconnecting or connecting the battery,
ignition wires, or test equipment leads
Disconnecting fuel injection system wiring
Washing the engine or engine
compartment.

BEFORE cranking the engine at starting RPM
(e.g. for compression testing) disable ignition
and fuel injection systems:
Disconnect connector for ignition coil power
Pa
ge 10 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

output stage, and fuse for fuel pump.
Disconnect harness connectors from all fuel
injectors.
Afterward, erase Diagnostic Trouble Code
(DTC) memory.
Pa
ge 11 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

24-11

CAUTION!

BEFORE disconnecting the battery:

Stop the engine.
Be sure the ignition is switched OFF (also
applies when connecting the battery). Failure
to do so may damage the Engine Control
Module (ECM).
Be sure of the proper radio code (for vehicles
equipped with coded anti-theft radio).

Be sure the battery negative (-) cable is
disconnected, when:
Working on the electrical system
Resistance (spot) welding or electric arc
welding anywhere on the vehicle.

When connecting and disconnecting
electrical test equipment (LED voltage tester,
multimeter, etc.):
Be sure the ignition is switched OFF.
Use correct adapters from the VW1594
Pa
ge 12 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

connector test kit.

For any work affecting the Engine Control
Module (ECM):
BEFORE disconnecting the ECM harness
connector, switch the ignition OFF and WAIT
at least 20 seconds. Failure to do so may
damage the ECM.
DO NOT connect any outside voltage source
to stimulate an output signal at the ECM.
Pa
ge 13 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

24-12

Rules of cleanliness


CAUTION!

Whenever carrying out work on the fuel
supply and fuel injection systems, carefully
observe the following rules of cleanliness.

- Thoroughly clean fuel system line and hose
connections and the surrounding area before
disconnecting.

- Place removed components on a clean surface
and cover. Use plastic sheeting or paper. Do not
use fluffy rags that could leave lint!

- Carefully cover over or seal any components
that have been opened if repairs are not carried
out immediately.

- Install only clean parts:


Do not remove replacement parts from the
packaging until immediately before they are
to be installed.

Do not use parts that have been stored
without packaging (e.g. in toolboxes, etc.).
Pa
ge 14 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

- When the fuel system is opened:


Avoid working with compressed air
whenever possible.

Avoid moving the vehicle if possible.
Pa
ge 15 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1

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)
Pa
ge 16 of 166 Motronic Multi
port Fuel In
jection
(MFI
) and i
gnition s
ystem
11/23/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU03.24.1