BMW 540i 1998 E39 Workshop Manual

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160 Fuel Tank and Fuel Pump
General ........................... .I6 0.2
Special tools ........................ .I6 0.2
Fuel pump ......................... .I6 0.3
Fuel tank evaporative control system ..... .I6 0.3
Evaporative system troubleshooting ..... .I6 0.4
Warnings and cautions ................ .I6 0.5
Fuel System Troubleshooting ...... .I6 0.6
Fuel pump fuse and relay .............. .I6 0.6
Operating fuel pump for tests ........... .I6 0.6
Fuel pump electrical circuit, testing ...... .I6 0.7
Fuel pump power consumption, testing ... .I6 0.9
Fuel pressure gauge, installing
(6-cylinder models)
................. .I6 0.1 0
Fuel pressure gauge, installing
(V-8 models) ....................... .I6 0.1 1
Fuel delivery, testing ................ .I6 0.12
Fuel Pump and Fuel Level Sender . . 160-15
Fuel level sender (right side) and
fuel pump. removing and installing
...... 160-15
Fuel level sender (left side).
removing and installing
............... 160-17
Siphon pump. removing and installing .... 160-1 9
Fuel Tank and Fuel Lines .......... 160-20
Fuel tank. draining ................... 160-20
Fuel tank. removing and installing ....... 160-21
Fuel expansion tank. removing
and installing
....................... 160-23
Activated carbon canister I fuel tank
leak detection unit
(LDP or DMTL).
removing and installing ............... 160-24
Running losses (312-way) valve.
removing and installing
............... 160-24

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This repair group covers service information specifically for the fuel supply system. Information on the fuel injection sys-
tem is covered in
130 Fuel Injection.
In the descriptions and procedures given below, engine and
engine management (DME) systems are referred to by man-
ufacturer code. If necessary, see
100 Engine-General for
model year, engine code, and DME applications.
NOTE-
Fuel filter replacement is covered in 020 Maintenance,
Special tools
Some of the procedures in this group require the use of
special tools.
I( Fuel line clamp 13 3 010 (Tool No. BMW 13 3 01 0)
4 Fuel pressure gauge T-fitting with shut-off valve
(Tool No. BMW 13
5 220)

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Fuel Tank and Fuel Pump
Fuel pump
The electric fuel pump is mounted in the fuel tank in tandem
with the right side fuel level sender. The fuel pump delivers
pressurized fuel to the fuel injection system.
A pressure regu-
lator maintains system pressure. The quantity of fuel supplied
exceeds demand, so excess fuel returns to the fuel tank via a
return line. See
130 Fuel Injection for more information.
NOTE-
Fuel pump removal procedures are given under Fuel level
sender (right side) and fuel pump, removing and install-
ing.
Fuel tank evaporative control system
Evaporative control, also referred to as running losses con-
trol, is designed to prevent fuel system evaporative losses
from venting into the atmosphere.
The components of this system allow control and monitoring
of evaporative losses by the on-board diagnostic
(OED II)
software incorporated into the engine control module (ECM).
NOTE-
1997 V-8 models (540i) with Bosch DME M5.2 are not
equipped with an
OBD I1 running losses monitoring system.
Fuel tank evaporative
control system
(models with
DME MS42.0)
4 The main components of the evaporative control system and
their functions:
Fuel overflow
tank acts as a liquidlvapor separator
Carbon canister stores evaporated fuel.
Plumbing ducts vapors from fuel tank to canister and from
canister to intake
manifold.
- Carbon canister purge valve is controlled by enginecontrol
module (ECM).
Running losses or 312-way valve (not shown) shunts ex-
cess fuel volume directly
back to fuel tank before it circu-
lates through injector fuel rail (models with Siemens MS42
or Bosch M5.2.1 engine management only).
Leak detection unit (LDP or DMTL) pressurizes fuel
tank
and evaporative system to monitor system leaks (models
with Siemens MS42 or Bosch M5.2.1 and later).
Leak detection systems vary among models and years, and
are further described in
130 Fuel Injection.
NOTE -
"3/2-way valve", 'tunning losses valve" and "fuel changeover
valve" are used interchangeably
in BMW technical literature.

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Fuel Tank and Fuel Pump
Evaporative system troubleshooting
- Start by accessing diagnostic trouble codes (DTCs) using a
BMW or BMW compatible aftermarket scan tool.
For purposes of OBD
II emissions compliance, the DME
system sets a diagnostic trouble code (DTC) when it de-
tects a leak that is equal or larger than minimum
lealc
sensed by system.
Malfunction Indicator Light (MIL) is illuminated upon sec-
ond recurrence of fault. See OBD On-Board Diagnostics.
- When leak testing, observe following conditions to obtain
plausible results:
Fuel tank
'1, to 'I., full.
0 Vehicle parked for at least 2 hours to allow fuel to reach
room temperature.
Ideal fuel temperature is 10"- 20°C
(50"
- 68" F).
Do not refuel immediately before
lealc test.
- If a leak is detected, check the following areas:
* Fuel filter cap (leaking or off).
Fuel tank ventilation lines leaking at fuel
tank or activated
carbon canister.
i
Tank ventilation valve leaking (in engine compartment).
Fuel level
sensorlfuel pump cap leaking.
Evaporative system component replacement is covered later
in
th~s group in Fuel Tank and Fuel Lines.

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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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.-- -
/ Fuel Tank and Fuel Pump - .. -. -- 1
Fuel pump fuse and relay
Troubleshooting of any fuel pump fault should begin with
checking the fuel pump fuse and the fuel pump relay. The
DME main relay should also be checked. The fuel pump relay
is located behind right side luggage compartment interior
panel.
I Fuel pump relay
BLU =blue ERN = blo$,m GRN =groan GRY = grsy ORG =orange PNI< =pink RED =red VIO =violel WHT = wlilte
rk-; I I 1 ECM
I I I 31 8 ,._--___.I
NOTE-
Special tools are required for some of the tests described
here.
4 Fuel pump circu~t is fuse-protected.
0 6-cylinder models with Siemens DME MS41 .I, MS42, V-8
models with Bosch DME M5.2, M5.2.1 englne manage-
ment: Fuse
F54,15A (luggage compartment fuse panel)
6-cylinder models with Siemens DME MS43 engine man-
agement: Fuse
F22,25A (glove compartment fuse panel)
V-8 models with Bosch DME M7.2: Fuse F54,25A (lug-
gage compartment fuse panel)
- Fuse 31 in glove compartment fuse panel supplies power to
coil side of fuel pump relay. Engine control module (ECM)
supplies switched ground to relay. During starting, fuel pump
runs as long as ignition switch is in START position and con-
tinues to run once engine starts. If electrical system fault in-
terrupts power to fuel pump, engine will not run.
. .
Operating fuel pump for tests
- To operate fuel pump for testing purposes without having to
run engine, bypass fuel pump relay to power pump directly.
< To run fuel pump, open luggage compartment and release
right side trim panel.

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- Fuel Tank and Fuel pump]
Remove fuel pump
relay (arrow).
4 Connect relay socitet terminal 6 (redlviolet wire) to relay
socket terminal
2 (whitelblue wire) with a fused jumper wire.
After completing tests, remove jumper harness.
CA
UTIOG
Relay locations may vary Use care when identifying relays
and making electrical checks at
the fuse/relay panel. See
610 Electrical Component Locations for additional re-
lay information.
The fuel pump relay has a 1.5
md red/violet wire at
terminal
6 in the relay socket. Terminal2 has a 2.5md
white/blue wire. See ELE Electrical Wiring Diagrams
for additional wiring information.
NOTE-
* The fuel pump will run as soon as the jumper wire Is at-
tached.
The jumper wire should be 1.5
md (14 ga.) and include
an in-line fuse holder with a 15A fuse. To avoid
fuse/relay
panel damage from repeated connecting and disconnect-
ing, also include a toggle switch in the jumper harness.
- If pump does not run with jumper installed, fault could be in
fuel pump, fuses
F31 or F22 1 F54, or wiring to pump. Check
pump, fuses and its wiring as described below.
Fuel pump electrical circuit, testing
- The test given below assumes that the fuel pump relay circuit
is functioning correctly as described earlier. Access to the
pump is from below the rear seat bottom cushion.
- Remove rear seat lower cushion by lifting front edge off left
and right catches.

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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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I Fuel Tank and Fuel Pump --
Fuel pressure gauge, installing
(6-cylinder models)
4 Remove fuel rail cover by prying off trim covers (arrows) and
removing nuts.
4 If equipped, remove schraeder valve cap (arrow). Blow fuel
back through feed line using a brief burst of compressed air
(maximum
3 bar or 43.5 psi).
WARNING -
Fuel in fuel line is underpressure (approx. 3 - 5 bar or 45 -
75psi) andmay be expelled underpressure. Do not smoke
or work near heaters or other fire hazards. Keep a fire ex-
tinguisher handy Before disconnecting fuel hoses, wrap a
cloth around fuel hoses to absorb any leaking fuel. Catch
and dispose of escaped fuel. Plug all open fuel lines.
Always unscrew the fuel tank cap to release pressure
in the tank before working on the tank or lines.
4 Attach fuel pressure gauge to BMW special tool 13 5 220
(T-fittlng) or equivalent and attach to schraeder valve.
WARNING -
The fuel pressure gauge must be securely connected to pre-
vent it from
coming loose underpressure.
CAUTION-
When using the BMWspecial tool, use care when turning the
T-handle in to open the schraeder valve. Screw the handle in
just until the schraeder valve opens. Turning the handle in too
far will damage the schraeder valve.
NOTE-
* The schraeder valve must be opened to the fuel pressure
gauge connection. Either remove the valve using a stan-
dard tire valve removal tool or use the BMW special tool
15 5 220.
* The fuel pressure gauge should have a minimum range of
0 to 5 bar (0 to 75 psi).
- For vehicles without the schraeder valve on the fuel rail, at-
tach the fuel pressure gauge in line with the fuel supply line
to the fuel rail.