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Fuel Injection I
The PWG potentiometers provide DC voltage signals as in-
put to the ME 7.2 control module for throttle and idle control
functions. Potentiometer signal
1 is the primary signal, poten-
tiometer 2 is used for a plausibility cross-check.
1. Potentiometer 1 ground
2. Potentiometer
1 power
3. Potentiometer 2 ground
4. Potentiometer 2 power
5. Potentiometer 1 signal to ECM
6. Potentiometer 2 signal to ECM
If errors are detected between potentiometer
1 and 2, the
ECM calculates the engine intake air mass (from
MAFsensor
signal) and only utilizes the potentiometer signal that closely
matches the detected
intake air mass. The ECM control mod-
ule uses the air mass signal for a comparative source to pro-
vide fail-safe operation.
If the ECM cannot calculate a
plausible conclusion from the monitored potentiometerthe
EDK motor is switched off and fuel injection cut-out is activat-
ed (no fail-safe operation possible).
EDK is continuously monitored during all phases of engine
operation. If faults are detected, the EDK motor is switched off
and fuel injection cut off is activated. The engine continues to
run extremely roughly at idle speed.
EDK adaptation
When the EDK throttle assembly is replaced, the adaptation
values of the previous EDK must be cleared from the ME 7.2
ECM using the BMW service testeroran equivalentscan tool.
Once the old adaptation values have been cleared, the new
EDK assembly should be installed and adapted as follows:
0 Switch ignition OFF for 10 seconds.
* Switch ignition ON. Afler approximately 30 seconds, the
EDK is briefly activated indicating that the replacement unit
is now adapted to the ME 7.2 system.
NOTE-
This EDK adaptation procedure is also necessary after re-
placing the
ME 7.2 engine control module. However, the ad-
aptation values do not require clearing since they have not
yet been established.
ECM relay, testing
The engine control module (ECM) relay is energized via the
ECM and supplies battery positive
(B+) power to many of the
engine management components and subsystems. If this re-
lay is faulty, the engine will not start.
NOTE-
The ECM relay is also referred to as the DME main relay
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130-70
Fuel Injection
ECM relay
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CAUTION-
Relay positions can vary Be sure to confirm relay position by
identifying the wiring in the
socl(et using the wiring diagrams
in ELE Electrical Wiring Diagrams.
Working in right rear of engine compartment:
Release interior ventilation filter cover latch
(A) and re-
move cover.
Release plastic locking tab
(B).
Rotate duct inward (arrow) to unlock from bulk head and
remove duct.
Release spring
loclt (C) to remove lower filter housing.
Slide filter housing away from inner fender to remove.
- Remove electrical box (E-box) cover fasteners and remove
cover.
4 With ignition off, remove main relay (arrow) in electronics
box (E-box) at right rear of engine compartment.
NOTE-
Relay locations can vary Confirm relay identification by
matching wiring colors and terminal numbers.
4 Check for voltage at terminal 6 of main relay socket (30-red
wire).
If battery voltage is present, continue testing.
If battery voltage is not present, check large red wire in re-
lay socltet. See ELE Electrical Wiring Diagrams.
- Reinstall relay and turn ignition on. Gain access to underside
of relay socket and check for ground at terminal
4 (85-brown
wire).
If ground is present, continue testing.
If ground is not present, switched ground signal from ECM
is missing. Check wire between ECM and relay.
- With ignition on and relay installed, check for battery voltage
at terminal
2 (87-redlwhite wire).
If battery voltage is present, relay has energized and is
functioning correctly.
If battery voltage is not present and all earlier tests are OK.
relay is faulty and should be replaced.
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130-72
Fuel Injection
I Oxygen sensors, replacing
4 Four Bosch oxygen sensors (2 precatalytic converter sen-
sors and
2 post-catalytic converter sensors) provide a vary-
ing voltage signal
[0.2 vdc (max. lean) to 0.8 vdc (max. rich)]
to the ME
7.2 ECM representing oxygen content in the ex-
haust gas.
WARNING-
Exhaust manifolds and pipes can be hot enough to cause se-
rious burns. Wear suitable heavy gloves and other appropri-
ate protection.
- Using a special oxygen sensor socltet, remove the threaded
sensors from the exhaust system.
- If not already applied, coat the new oxygen sensor threads
with an anti-seize compound before installation. Do not get
compound on the sensor tip.
Tightening torque
Oxygen sensor to exhaust system
50 Nm (37 ft-lb)
Fuel injectors, removing and installing
The ME 7.2 system uses ball seat type fuel injectors. This de-
sign
prov:des precise seal'ng when the iniector is closed
therebv eiminalinq raw HC (unb~rned fue ) formalion in tne
intake.-~he fuel inkctors areswitched on and off by the ECM
at the ground side.
- Remove plastic cover from above fuel rail. See100 Engine
Removal and Installation.
- Disconnected battery negative (-) cable.
CAUTION-
Prior to disconnecting the battea read the battery discon-
nection cautions given at the front of this manual. See 001
General Warnings and Cautions.
- Remove both ignition coil covers.
Disconnect ignition coil connectors.
Remove left and right ignition coil ground wires,
4 Remove fuel injector loom boxes.
Loosen mounting fasteners
(A).
Disconnect electrical plugs (B and D).
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Fuel Tank and Fuel Pump
Warnings and cautions
Observe the following warnings and cautions when servicing
the fuel system.
WARNING-
* The fuel system is designed to retain pressure even when
the ignition is off. When working with the fuelsystem, loos-
en the fuel lines slowly to allow residual
fuel pressure to
dissipate. Avoid spraying fuel. Use shop rags to capture
leaking fuel.
Before beginning any work on the fuel system, place a
fire extinguisher in the vicinity of the work area.
Fuel is highly flammable. When working around fuel, do
not disconnect any wires that could cause electrical
sparks. Do not smoke or worknearheaters or other fire
hazards.
* Always unscrew the fuel tank cap to release pressure
in the
tanlc before working on the tank or lines.
When disconnecting a fuel hose, wrap shop rag around
end of hose to prevent spray of fuel under pressure.
Do not use a work light with an incandescent bulb near
any fuel. Fuel may spray on the hot bulb causing a fire.
0 Make sure the worlc area is properly ventilated.
CAUTION-
- Prior to disconnecting the battery, read the battery discon-
nection cautions given in
001 General Cautions an4
Warnings.
Before
making any electrical tests with the ignition
turned on, disable the ignition system as described in
120 Ignition System. Be sure the battery is discon-
nected when replacing components.
To prevent damage to the ignition system or other DME
components, including the engine control module
(ECM), always connect and disconnect wires and test
equipment with the ignition off.
Cleanliness is essential when
worl~ing with the fuel sys-
tem. Thoroughly clean the fuel line unions before dis-
connecting any of the lines.
Use only clean tools. Keep removed parts clean and
sealed or covered with a clean, lint-free cloth, especial-
ly if completion of the repair is delayed.
Do not move the car while the fuel system is open.
Avoid using high pressure compressed air to blow out
lines and components. High pressure can rupture inter-
nal seals and gaskets.
Always replace seals, O-rings and hose clamps.
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160-8
I Fuel Tank and Fuel Pump
4 Disconnect harness connector from tank sending unit by
sliding connection lock to release connector.
Connect voltmeter between fuel pump terminals on
connector.
NOTE-
Fuel pump power (+) is supplied through the white/blue wire
Ground
(-) is supplied by the brown wire.
With jumper wire connected in place of fuel pump relay as
described above, check for battery voltage at fuel pump
harness connector terminals.
If voltage and ground are present, fuel pump is probably
faulty. If there is no voltage, check wiring between fuel pump
and relay.
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Fuel Tank and Fuel purnpl
Fuel pump power consumption, testing
To achieve accurate test results, the battery voltage at the
fuel pump connector should be
12.6 volts. Charge the battery
as necessary.
A higher than normal power consumption may indicate a
worn fuel pump, which may cause intermittent fuel starvation
due to pump overheating and seizure. The only remedy is
pump replacement.
A lower than normal power consumption
may indicate a blockage. Be sure to check that the return line
and the pump pickup are not obstructed before replacing the
pump.
- Expose right side access cover:
Peel forward lip of carpet.
Release rubber grommet from center of access cover insu-
lation.
Peel back insulation at perforations to expose fuel tank ac-
cess cover.
Remove right side cover to expose electrical harness con-
nector.
Disconnect harness connector from tank sending unit by slid-
ing lock back. Lift off connector.
Test fuel pump for current draw by attaching digital ammeter
between pump and harness (terminal
2, whitelblue wire) and
connect a jumper wire between pump and harness (terminal
1, brown wire) as shown.
CAUTION-
Do not allow the test leads to short to ground.
NOTE-
See 600 Electrical Systern-General for information on elec-
trical tests
using a digital multirneter.
Run pump as described in Operating fuel pump for tests.
- Compare ammeter reading with specification listed in ac-
companying table.
Fuel
pump current
Current consumption (average) 9.5 amps
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err- .- Fuel Tank and Fuel Pump
FUELPUMP AND FUELLEVELSENDER
E39 models use a two-lobed fuel tank. Each lobe of the tank
has its own fuel level sending unit. Each sender has a float
connected to a variable resistance wipercontact. To equalize
fuel level between the two
tank lobes, a siphon pump is in-
stalled in the left lobe.
When replacing asender or fuel pump, always replace hose
clamps,
gasltets and O-rings.
WARNING
-
When removing the fuel level sender or the fuel pump, the
fuel tank should be drained to
1/4 capacity or below as de-
scribed later in this repair group.
NOTE-
The compensating siphon pump maintains the fuel level be-
tween the right and left tank lobes. If fuel level sender resis-
tances are not approximately the same on left and right,
remove the senders and visually inspect the level in each
lobe. If the levels are different, check the siphon pump.
Fuel level sender resistances
Float position
l~est results (Q
Down (empty) 150- 70
Up (full) 1401 -415
Fuel level sender (right side) and fuel
pump, removing
and installing
- Drain fuel from tank as described later.
- Disconnect negative cable from battery.
CAUTION-
Prior to disconnecting the battery, read the battery discon-
nection cautions given in
001 General Cautions and
Warnings.
- To access top of fuel tank, remove rear seat lower cushion by
lifting front edge
off catches.
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I Fuel Tank and Fuel Pump
The plastic fuel tank is mounted underneath the center of the
car (underneath the rear seat). Mounted in the fuel tank are
the fuel pump and fuel level sending units. Connecting lines
for the evaporative emission control system and expansion
tank are also attached to the tank.
Fuel
tank capacity for E39 models
Tank capacity
70 liters (18.5 gal)
Reserve capacity
8 liters (2.1 gal)
Fuel tank, draining
Drain fuel tank into a safe storage unit using an approved fuel
pumping device.
WARNING-
# Before removing tank, be sure that all hot components,
such as the exhaust system, are completely cooled down.
Fuel may be spilled. Do not smoke or
work near heat-
ers or other fire hazards.
- Start engine and allow to run 10 - 15 seconds to fill fuel com-
pensating siphon assembly. This will allow both lobes of fuel
tank to he drawn off through fuel filler pipe,
- Disconnect negative cable from battery.
CAUTION-
Prior to disconnecting the batteg read the battery discon-
nection cautions given
in 001 General Warnings and Cau-
tions.
- Remove fuel tank filler cap
- Slide suction hose into filler neck about 130 cm (51 in.), twist-
ing as necessary. Withdraw fuel into storage unit.
- Monitor fuel level reduction in both lobes:
- Remove rear seat cushion and access both fuel tank send-
er harness connectors.
Use multimeter to measure resistance at both senders,
Resistance should drop as fuel level drops.
- If siphoning mechanism is faulty, drain left tank lobe sepa-
rately by removing sender cover and pumping fuel directly
out of left lobe.