Checking Fuel Pump and Bypass Valve
CHECKING FUEL PUMP AND BYPASS VALVETest values
Fuel bypass valve
Opening pressure in bar gauge pressure
at idle speed 0.6-0.8
at 3000 rpm min. 1.3
Special tools
Measuring negative pressure
1. Connect tester to fuel inlet (1) on fuel pump. For this purpose, remove fuel feed line. Vent injection system. Service and Repair
Measure vacuum pressure at idle speed. To do so, use clip to nip hose (arrow) at tester downstream of pressure gage.
If system fails to reach value of 0.1 bar vacuum, exchange suction and delivery valves or fuel pump. Removal and Installation of Injection Timing Device
Checking fuel feed pressure
2. Unscrew fuel line (3) on fuel main filter.
3. Connect tester. For this purpose, connect fuel line to hose line for tester with a double hollow screw and closing nut. Connect other hose line of tester to fuel filter.
4. Vent injection system. Service and Repair
5. Warm up engine.
6. Measure fuel feed pressure at idle speed and 3000 rpm.
0.6-0.8 bar gauge pressure at idle speed.
Min. 0.8 bar gauge pressure at 3000 rpm.
7. What to do in case feed pressure is inadequate:
a) Check bypass valve, removing, disassembling and cleaning for this purpose.
Increase preloading of compression spring (2), lengthening spring to 26-27 mm.
b) Check fuel filter for clogging. If necessary, fit new filter element with body (3) and sealing ring (4).
c) Exchange suction and delivery valves or fuel pump.
Checking final fuel feed pressure
8. Using clip (arrow), nip fuel return hose.
9. Measure final fuel feed pressure at idle speed and 3000 rpm.
Min. 1.1 bar gauge pressure at idle speed.
Min. 1.3 bar gauge pressure at 3000 rpm.
10. If final feed pressure is inadequate, exchange suction and delivery valves or fuel pump.