1999 BMW 525i Workshop Manual

Downloaded from www.Manualslib.com manuals search engine
7 .- A Fuel Tank and Fuel Pump
Siphon pump, removing and installing
The fuel compensating siphon pump equalizes fuel level
between the two fuel tank lobes.
- Drain fuel tank as described later,
WARNING -
Fuel may be spilled. Do not smoke or work near heaters or
other fire hazards.
- Remove left and right fuel level sensors and fuel pump as
described earlier.
4 Once left side level sensor unit has been lifted partially out
of tank, disconnect tank siphon hose by pressing tabs
(arrows).
- The tank lobe siphon pump is held to baffle in bottom of right
tank lobe. Release retainer and lift out pump.
- Installation is reverse of removal.
Attach siphon pump to right side baffle.
Attach tank siphon hose to left sender unit firmly.
Use new sealing ring at tank collars
Be sure that fuel sender floats point in same direction as
during removal.
Reconnect harness connectors.
. Before starting engine, fill fuel tank with at least 5 liters
(1.5 gallons) of fuel.
Check for
leaks by running engine.
Afler finishing repairs but before starting engine, be sure

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
Fuel Tank and Fuel pump/
- Remove suction hose from tank filler neck carefully to avoid
damaging filler neck baffle plate.
CAUTION-
After finishing repairs but before starling engine, be sure
there is at least
5 liters (1.5 gallons) of fuel in tanlc. The fuel
pump will be damaged if run without fuel.
Fuel tank, removing and installing
- Remove fuel tank filler cap and drain tank as described
earlier.
- Disconnect negative cable from battery.
CAUTION-
Prior to disconnecting the battea read the battery discon-
nection cautions given in
001 General Cautions and
Warnings.
- Remove rear seat bottom cushion. Peel forward lip of carpet
from beneath seat cushion and carefully peel back insulation
to expose fuel tank access cover on left and right sides. Re-
move covers.
Disconnect right side supply hose and
electr~cal harness
connector (arrows).
D~sconnect left side return hose and electrical harness
connector.
Working inside car, disconnect parking
bralte cable ends
from parking brake lever. See
340 Brakes.
Lift car and support safely.
Make sure the car is stable and
we/ supported at all times.
Use a professional automotive lift
orjack stands designed for
the purpose. A floorjaclc is not adequate support.
- Remove complete exhaust system and heat shield. See 180
Exhaust System.
- Remove drive shaft. See 260 Driveshaft

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