Component Tests and General Diagnostics

Checking Fuel Pump Delivery Pressure (M54)

Switch off ignition.


CAUTION:
The fuel in the fuel lines is under pressure (approx. 3 bar)!
Catch and dispose of escaping fuel.


Remove cover from fuel injectors.







Remove dust cap (1) from measuring valve on fuel rail.







Prepare special took kit 13 5 220 (consisting of 13 5 221 and 13 5 222).







Unscrew check valve (1) on special tool kit 13 5 220. Fit special tool kit 13 5 220 on measuring valve and tighten knurled nut until hand-tight.
Start engine.
Screw in check valve (1) until a pressure reading is indicated on DIS Tester.


CAUTION: Do not under any circumstances screw in the check valve up to the mechanical stop. This could damage the valve in the pressure regulator housing.


Measuring fuel pressure:
- Connect pressure sensor to DIS Tester
- Start engine.
- Select Measurement.
- Multimeter function appears
- Select Pressure test
- Read off fuel pressure
Compare actual value of test pressure with specified value.
Switch off engine.

Checking fuel pump:
Detach fuel pump relay.


NOTE: Check whether fuel pump no longer starts up during engine starting procedure (engine tails to start).







Connect special tool 61 3 050 to terminal (87) and terminal (30).
Press button and read off fuel pump delivery pressure on DIS Tester.
Compare actual value with specified value of delivery pressure.







Keep special tool 13 3 010 ready for further tests.
Further tests are described in the section "Fuel pressure check".


NOTE:
Interrogate fault memory of DME control unit.
Check stored fault messages.
Rectify faults.
Then clear fault memory.