Measuring vacuum
1. Connect tester at fuel input (1) on fuel pump. For this purpose, remove fuel feed line. Vent injection
system (07.1-140).
Measure vacuum a t idle speed. For this purpose, pinch hose (arrow) on tester behind pressure gauge with a clamp.
If the value is not attained, replace suction and pressure valves or replace fuel pump (07.1-235).
Checking fuel delivery pressure
2. Unscrew fuel line (3) between fuel pump and fuel main filter.
3. Connect tester. For this purpose, connect fuel line together with hose line for tester to a double hollow screw and closing nut. Connect other hose line of tester to fuel filter.
4. Vent injection system (07.1-140).
5. Run engine to operating temperature.
6. Measure fuel delivery pressure at idle speed and at 3000lmin.
At idle speed 0.6-0.8 bar gauge pressure.
At 3000/rnin at least 0.8 bar gauge pressure.
7. If delivery pressure is too low:
a) Check overflow valve, while removing, disassembling and cleaning overflow valve on injection pump.
Increase preload of compression spring (2). For this purpose, lengthen compression spring to 26-27 mm.
1. Ball
2. Compression spring
3. Housing
4. Sealing ring
5. Closing plug
b) Check fuel filter for contamination. Mount new filter element with housing (3) and gasket (4), if required.
c) Replace suction and pressure valve or replace fuel pump (07.1-235).
Checking fuel delivery end pressure
8. Pinch fuel return hose with a clamp (arrow)
9. Measure fuel delivery end pressure at idle speed and at 3000lmin.
At idle speed min. 1.1 bar gauge pressure.
At 3000tmin a t least 1.3 bar gauge pressure.
10. If the delivery end pressure is too low, replace suction and pressure valves or replace fuel pump
(07.1 -235).
