Fuel Pressure, Checking

Fuel Pressure, Checking

- Read safety precautions before beginning work.
- Observe Clean Working Conditions.
- Remove high pressure in fuel system.

CAUTION: Fuel supply line is under pressure. Wear protective goggles and protective clothing to prevent injuries and contact with skin. Before removing from hose connection wrap a cloth around the connection. Then release pressure by carefully loosening the union nut.







- Place a cloth around connection and loosen union nut - arrow - to reduce fuel pressure.
- Then tighten threaded connection again.
- Connect a Pressure Tester with Adapter, as shown.







- Make sure hose clamps are seated securely.
- Open shut-off valve of pressure gauge set. The lever points in the direction of flow.







- Remove nuts - 1 - on right side of fuel delivery unit cover. If necessary, remove backrest support - 2 - or mounting bracket.







- Disconnect connector from Fuel Pump (FP) Control Module J538 - 5 -.
- Disconnect harness connector - 3 - from flange of fuel delivery unit.







- Connect Hand held remote starter (jumper) with adapter cables from connector test kit to terminal - 1(+) - of Fuel Pump (FP) and to terminal - 3(+) - of harness connector of Fuel Pump (FP) Control Module J538.
- Connect terminals - 4(-) - of harness connector and - 4(-) - of Fuel Pump (FP) using an adapter cable from connector test kit.
- Switch ignition on.
- Operate Hand held remote starter (jumper) and observe display of pressure tester while doing this.

Fuel pressure must increase up to a maximum pressure of 6 bar:

NOTE: When releasing control button of remote control, fuel pressure decreases to approx. 5.6 bar.

If fuel pressure is OK, check residual pressure.

If specification is exceeded:
- Pressure relief valve in sensor flange faulty, replace sensor flange.

If specification is not obtained:
- Check fuel lines for possible restrictions (kinks) or blockages.
- Check all fuel lines in fuel tank for leaks.
- Check fuel filter for leaks.

If no malfunction can be found:
- Replace sensor flange with pressure relief valve.
- Repeat test.

If fuel pressure is not obtained again:
- Fuel Pump (FP) faulty, replace fuel delivery unit.