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944 S/944 S2 Fuel System - Electronic Control
24/28
Test Point 18: Fuel Pressure
Fuel collection pipe has a test
connection at left front. Unscrew
cap nut of the test connection.
Important! Inserted ball seal could
fall out!
Connect P 378 pressure tester on
the test connection. Start the
engine. Vacuum on pressure
regulator at idle speed:
Test pressure: 3.3 +- 0.2. bar
Hot starting problems:
Check with the engine stopped and fuel pump
running, without vacuum on the pressure regulator
(this requires removing the DME relay and bridging
terminals 87b and 30):
Test pressure: 3.8 +- 0.2 bar
-
Stop fuel pump. Read pressure on the pres
sure tester (specitication: 3.8 +- 0.2 bar).
- Max. permissible pressure drop on warm
engine: 0.5 bar in 30 minutes.
- It the pressure drops below the specitied
value, proceed as described below.
Build up pressure again by switching on the fuel pump briefly. Remove return pipe on the
pressure regulator (fuel pump must not be switched on).
DME - Diagnosing/Troubleshooting
Printed In Germany - XXI, 1989
D 24/28 - 21