Fuel Delivery, Testing - BMW 5251 Service Manual

Fuel Tank and Fuel Pump
Fuel delivery, testing
Checitino fuel d e l i v e ~ is a fundamental oart of troubleshoot-
. .
ing and diagnosing thk DME system. ~ u k l pressure directly
influences fuel delivery. An accurate fuel pressure gauge will
be needed to make the tests.
There are two significant fuel deliveryvalues to be measured:
*
System pressure
-
created by fuel pump and maintained
by pressure regulator
Residual pressure
-
pressure maintained in closed sys-
tem after engine and fuel pump are shut off
if proper system pressure and residual pressure are present,
also check for problems in fuel delivery volume, which can be
affected by restrictions such as clogged fuel filter or fuel pick-
up port in the fuel tank.
System pressure, testing
1. Fuel pressure regulator outer seal
4
System pressure is created by the fuel pump and maintained
2. Vacuum line connection.
3. Fuel pressure regulator Inner seal.
4. Fuel flow back to fuel tank.
5. Fuel flow from fuel pump.
Fuel pressure regulator
Fuel pressure regulator locations
M52
In fuel injector rail, in engine
compartment
M52 TU
In
312
way valve, below vehicle under
driver seat
by the pressure regulator. System pressure is not adjustable.
M54
In fuel filter
M62
to
9/97
In fuel injector rail, in engine
compartment
M62
from
9/97
to
9/98
In
312
way valve, below vehicle under
driver seat
M62 TU
from
9/98
In fuel filter, below vehicle under driver
seat