Test Point 20 - Fuel Pressure
TEST POINT 20: - Fuel pressurePossible Causes, Elimination, Remarks
The fuel collection pipe has a test connection at cyl. 1. Unscrew the cap nut of the test connection.
CAUTION: The inserted ball seal could fall out!
Connect the pressure gauge P 378 to the test connection. Start the engine and run at idle speed with vacuum at the pressure regulator:
Test pressure 3.3 ± 0.2 bar (50 ± 3 psi)
In the case of hot starting problems:
Perform the test with the engine stationary and with running fuel pump without a vacuum at the pressure regulator (to do this; remove the Digital Motor Electronics (DME) relay and jumper terminal 87b and terminal 30:
Test pressure 3.8 ± 0.2 bar (55 ± 3 psi)
- Switch off the fuel pump. Read off the pressure value on the pressure gauge (nominal 3.8 ± 0.2 bar).
- Max. permissible pressure drop with warm engine: 0.5 bar (7.25 psi) in 30 min.
- If the pressure drops below the specified value, proceed as described below:
Fuel Pump Diagnosis:
Build up pressure again by switching on the fuel pump briefly. Remove the return pipe.
CAUTION: The fuel pump must not be switched on when removing the return pipe.