fuel cap release BMW 525i 2001 E39 User Guide

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Fuel Tank and Fuel Pump
Fuel pressure gauge, installing
(V-8 models)
Remove engine cover by pressing down on pins (arrows) to
release cover locks.
4 Disconnect and remove fuel supply line from lefl side of fuel
rail by sliding
loclting collar in (arrows) and pulling lines
apart.
NOTE-
* ME2 TU and MS43 vehicles (1999 and later models) use a
non-return fuel line with only one line to the fuel
rafl.
BMW uses three styles of fuellfne connections; a one-use
clamp, a locking fitting that uses
BMWspeclal tool 16 1 050
to release, and a quick release sleeve (above) that discon-
nects the line when depressed.
WARNING -
* Fuel In fuel line is under pressure (approx. 3 - 5 bar or 45 -
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
lealiing 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 workina on the tank or lines.
< Install inline fuel pressure gauge.
WARNING -
The fuel pressure gauge must be securely connected to pre-
vent it from coming loose underpressure.
NOTE-
The fuel pressure gauge should have a minimum range of 0
to 5 bar (0 to 75 psi).

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Fuel Tank and Fuel Pump
4 Relieve system pressure and attach a fuel 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 under pressure (approx. 3 - 5 bar or 45 -
75psi) and may be expelled underpressure. Do not smoke
or
worlc 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.
- Operate fuel pump as described in Operating fuel pump for
tests. Compare fuel pressure to specifications in accompa-
nying table.
Fuel pressure specification
All E39 vehicles 3.5 +0.2 bar (50.76 i2.9 psi)
- If pressure is low, repeat test while gradually pinching off re-
turn hose to fuel tank. Pressure should rise rapidly. If not, fuel
pump is most likely faulty. If pressure rises, the fuel pressure
regulator is most
likely faulty.
- If pressure is too high, checlc return line from pressure regu-
lator to tank. Check for
ltinks in hose. If no faults can be
found, pressure regulator is most likely faulty.
CAUTION-
The fuel pump is capable of developing a higher pressure
than that regulated by the pressure regulator. In the event the
fuel pump checlc valve is faulty (stuck closed), male sure the
I fuel pressure does not rise above 6.0 bar (87psi). Damage
to the fuel lines or fuel system components could result.
- Reassemble engine, noting the following:
Remove fuel pressure gauge and fittings.
Replace schraeder valve, if removed
Replace fuel pump relay.
Replace fuel filler cap.
Residual pressure, testing
For quick restarts and to avoid vapor lock when the engine is
hot, the fuel injection system retains fuel pressure after the
engine is shut off. This residual pressure is primarily
rnain-
tained by the fuel pressure regulator and a checlc valve at the
fuel pump
outlet.

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. .
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.