Downloaded from www.Manualslib.com manuals search engine
. .
I Fuel Tank and Fuel Pump I
4 Relieve system pressure and attach afuel pressure gauge as
described in Fuel pressure gauge, installing (6-cylinder
models) or Fuel pressure gauge, installing
(V-8 models).
WARNING -
Fuel in fuel line is underpressure (approx. 3 - 5 bar or45 -
75psi) and may 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
- Start engine allow it to run for approximately one minute.
Note fuel pressure reading.
- Observe fuel pressure reading after approximately 20 mln-
utes. The pressure should not drop more than 0.5 bar from
system pressure listed in fuel pressure specifications in ac-
companying table.
Fuel pressure specification
Ail
E39 vehicles 3.5 i-0.2 bar (50.76 i2.9 psi)
- When finished, disconnect pressure gauge and fitting, and
replace schraeder valve, if removed.
- If fuel system does not maintain pressure:
Visually check for leaks in fuel lines and unions,
Check for leaking
injector(s).
Check for faulty fuel pump check valve.
- To test fuel pump check valve:
Repeat residual pressure test.
Immediately aftershutting off engine, pinch off fuel delivery
line using a fuel hose pinch clamp (BMW
13 3 010 or
equivalent).
If pressure is now maintained, fault is most likely at fuel
pump check valve.
If pressure again drops below specifications, fault is most
likely in fuel pressure regulator.
Downloaded from www.Manualslib.com manuals search engine
.- .
Fuel Tank and Fuel Pump
- To reinstall:
Use new sealing ring at tank collar.
* Align tab of sending unit with matching recess in opening
of tank.
Be sure that fuel line connections point in same direction
as they came out.
Reconnect harness connector and hose.
Fill tank and check for leaks by running engine.
Install access cover and its mounting fasteners.
CAUTIOI\C
After finishing repairs but before starting engine, be sure
there is at least
5 liters (1.5 gallons) of fuel in the tank. The
NOTE-
It is common practice to replace the fuel filter when the fuel
pump
unit is replaced. See 020 Maintenance.
Tightening torque
Tank collar locking ring to tank 35 Nm (26 lb-ft)
Fuel level sender (left side),
removing and installing
The procedure for removing and replacing the left side fuel
level sender is
simllar to that used for the r~ght side. There is
no fuel pump on the left side.
- Remove rear seat lower cushion by lifting off catches at front.
- Expose left side access cover:
- Peel forward lip of carpet.
Release rubber grommet from center of access cover
insulation.
Peel back insulation at
perforations to expose fuel tank
access cover.
Remove cover to expose electrical harness connector.
WARNING-
Fuel may be spilled. Do not smoke or work near heaters or
other fire hazards.
When disconnecting fuel hose, wrap shop rag around
end of hose to prevent spray of fuel under pressure.
Downloaded from www.Manualslib.com manuals search engine
--
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.
Downloaded from www.Manualslib.com manuals search engine
160-22
Fuel Tank and Fuel Pump
4 Working underneath car, pinch off supply and return fuel hos-
es (arrows), then disconnect hoses from rigid metal lines.
- Remove right rear wheel and wheel housing splash shield.
4 Worlting at right rear wheel housing, loosen hose clamp
(arrow) and disconnect filler pipe from tank.
- Support tank from below. Remove tank strap mounting bolts.
Lower and remove tank, disconnecting right side vent and
other
hoses/electrical connectors as necessary.
Always use new seals, gaskets, O-rings, and hose clamps.
lnspect hoses and replace any that are chafed,
dr~ed out or
cracked.
lnspect heat shield and replace if corroded.
Inspect rubber buffers and
hers on fuel tank, support
straps and on underside of body. Replace rubber parts that
are hardened or damaged.
- After finishing repairs but before starting engine, fill fuel tank
with at least
5 liters (1.5 gallons) of fuel.
CAUTlOI+
The fuelpump will be damaged if run without fuel.
* If the filler neck has been removed from the body, be
sure to reattach the
neck grounding screw (where ap-
plicable). Check electrical resistance between the
ground tab and wheel
hub. The resistance should be
no
hiaher than 0.6f2
Tightening torques
Fuel tank to body 23 Nm (17 ft-lb)
Hose clamp
8 -13 mm dia. 2 Nm (18 in-lb)
Hose clamp 13
- 16 mm dia. 3 Nm (27 in-lb)
Hose clamp 42
- 48 mm dia. 4 Nm (36 in-lb)
Downloaded from www.Manualslib.com manuals search engine
.- Fuel Tank and Fuel pump( -
Fuel expansion tank, removing
and installing
- Raise rear end of car and support safely.
CA U TIOG
Make sure the car is stable and well supported at all times.
Use a professional automotive lift
orjack stands designed for
the
ouroose. A floor iack is not adequate support
- Remove left rear wheel and wheel housing inner shield.
4 Remove plastic nut (A) and disconnect hose (B).
4 Tilt vent tank down and loosen or cut off hose clamps
(arrows). Pull hoses off fittings.
- Release vacuum line loclting clips and remove tank
- Installation is reverse of removal. Use new hose clamps.
Tightening torques
Hose clamp 8 - 13 mm dia. 2 Nrn (18 in-lb)
Hose clamp 13 - 16 mm dia. 3 Nm (27 in-lb)
Hose clamp
42 - 48 mm dia. 4 Nm (36 in-lb)
Downloaded from www.Manualslib.com manuals search engine
Fuel Tank and Fuel Pump 1
Activated carbon canister I fuel tank leak
detection unit
(LDP or DMTL), removing . . -
and installing
- Raise rear end of car and support safely.
CAUTION-
Make sure the car is stable and well supported at all times.
Use a professional automotive lift
orjack stands designed for
the purpose.
A floor jack is not adequate support.
- Remove left rear wheel and inner fender panel
Remove carbon canisterlfuel tank leak detection unit
(V-8 model shown):
Disconnect electrical harness connector
(A) from fuel tank
leak detection unit.
Pinch and remove quick-disconnect fittings at intake line to
air filter housing
(5) and hose to expansion tank (C).
* Remove mounting clamp and lower canister with fuel tank
leak detection unit.
Installation is reverse of removal.
Tightening
torques
Hose clamp 8 - 13 mm dia. 2 Nrn (18 in-lb)
Hose clamp
13 - 16 rnm dia 3 Nm (27 in-lb)
Running losses (312-way) valve,
removing and installing
The running losses (312-way) valve is located under the car
beneath the driver's seat, just ahead of the fuel filter. A protec-
tive covershieldsfuel system components from road hazards
and dirt.
The engine control module
(ECM) controls the operation of
the 312-way valve (pulse-width modulated). On engine start
up, the valve solenoid is energized for 20 seconds in order to
supply full fuel volume to the fuel rail.
After20 seconds, the
solenoid is deactivated and sprung closed (the bypass is
opened). This reduces the amount of fuel circulating through
the fuel rail and diverts the excess to return to the fuel tank
through the fuel pressure regulator.
The fuel injectors are supplied with pressurized fuel, but ex-
cess fuel is diverted to the fuel tank without first passing
through the fuel rail. This prevents the excess fuel from ab-
sorbing heat in the engine compartment, thus lowering the
temperature and amount of vaporization in the fuel tank.
Downloaded from www.Manualslib.com manuals search engine
160-25
Fuel Tank and Fuel pump1
The 312-way valve is also activated briefly if an engine misfire
is detected. This provides full fuel flow through the fuel rail to
determine if the misfire was caused by a lean fuel condition.
The valve is monitored by the ECM forfaults.
- Using BMW or compatible scan tool, read out fault memory.
See
OBD On-Board Diagnostics.
- Turn off ignition.
- Raise car and support safely.
CA UTIOW
Male sure the car is stable and well suppodedat all times.
Use a professional automotive lift
orjack stands designed for
the purpose.
A floor jack is not adequate support.
- Worlting under car beneath driver's seat, remove protective
panel from fuel filter and 312-way valve.
- Clamp off fuel lines at 312-way valve.
4 To remove 312-way valve (V-8 model shown):
Disconnect electrical harness connector
(A) from valve.
Remove vacuum hose
(B) from fuel pressure regulator.
* Remove hose clamps (arrows) and disconnect fuel lines.
Remove
M6 mounting nuts and lower 312-way valve.
WARNING-
Fuel will be spilled. Use shop rags to capture fuelas fuellines
are disconnected. Do not
smoke or work near heaters or oth-
er fire hazards.
- Installation is reverse of removal. Use new hose clamps
NOTE-
Install protective cover and seals correctly to keep moisture
and road dirt out of underbody fuel system components.
Tightening torques Hose clamps
8 - 13 mm dia.
2 Nm (18 in-lb)
Hose clamps
10 - 16 mm dia.
2 Nm (18 in-lb)
Hose clamps
18 mm dia. 3 Nm (27 in-lb)
Hose clamps 42
- 48 mm dia. 4 Nm 136 in-ib)
Downloaded from www.Manualslib.com manuals search engine
- -
On-Board Diagnostics
Professional diagnostic scan tools available atthe time of this
printing include the BMW factory tools
(DISplus, GTI,
MoDiC) and a small number of aftermarket BMW-specific
tools. See
020 Maintenance.
In addition to the professional line of scan tools, inexpensive
generic OBD
II scan tool software programs and handheld
units are readily available. Though limited, they are
nonetheless powerful diagnostic tools. These tools read live
data streams and freeze frame data as well as a host of other
valuable diagnostic data.
Diagnostic monitors
Diagnostic monitors run tests and checks on specific
emission control systems, components, and functions.
A complete drive cycle is requiredforthe tests to bevalid. See
Drive cycle in this repair group. The diagnostic monitor
signals the
ECM of the loss or impairment of the signal or
component and determines if a signal or sensor is faulty
based on
3 conditions:
* Signal or component shorted to ground
Signal or component shorted to
B+
Signal or component missing (open circuit)
The OBD
II system monitors all emission control systems that
are installed. Emission control systems vary by vehicle model
and year. For example, a vehicle may not be equipped with
secondary air injection, so no secondary air readiness code
would be present.
OBD
II software monitors the following:
Oxygen sensors
Catalysts
Engine misfire
- Fuel tank evaporative control system
Secondary air injection Fuel system
Oxygen sensor monitoring. When driving conditions allow,
response rate and switching time of each oxygen sensor is
monitored. The oxygen sensor heater function is also
monitored. The OBD
II system differentiates between
precataylst and post-catalyst oxygen sensors and reads each
one individually. In order
forthe oxygen sensor to be
effectively monitored, the system must be in closed loop
operation.