Residual Pressure, Checking

Residual Pressure, Checking

Special tools, testers and auxiliary items required
- High pressure fuel gauge

Test requirements
- Fuel pressure OK

CAUTION: Fuel supply line is under pressure. Wear protective goggles and protective clothing to prevent injuries and contact with skin. Before loosening hose connections, place rags around the connection point. Then release pressure by carefully pulling on hose.

Procedure







- Disconnect the fuel supply line - 2 - and catch leaking fuel using a rag.







- Install a High pressure fuel gauge in place of the fuel supply line.
- Open the shut-off valve of the High pressure fuel gauge.
- Switch the ignition on and off until the fuel pressure no longer increases.
- Check the indicated fuel pressure on the High pressure fuel gauge.

Specified value: 3.5 to 5.0 bar.

- Observe the pressure drop on the pressure gauge. Pressure must not fall below 3.0 bar within 10 minutes.

If pressure drops further:
- Switch the ignition on and off until the fuel pressure on no longer rises.







- Immediately close the shut-off valve of High pressure fuel gauge.

If the fuel pressure falls again:
- Check the fuel line to the high pressure pump for proper seal.

If no malfunction can be found:
- Replace the high pressure pump.

If the fuel pressure no longer falls:
- Check the fuel line to the fuel filter for proper seal.

If no malfunctions are found on the fuel line:
- Check the fuel pump check-valve.







- Connect a High pressure fuel gauge between the fuel filter and fuel supply line.
- Open the shut-off valve of the pressure gauge.
- Switch the ignition on and off until the fuel pressure no longer increases.
- Check the indicated fuel pressure on the High pressure fuel gauge.

Specified value: 3.5 to 5.0 bar.

- Observe the pressure drop on the pressure gauge. Pressure must not fall below 3.0 bar within 10 minutes.

If pressure drops further:







- Immediately close the shut-off valve of High pressure fuel gauge.
- Observe the fuel pressure drop on the pressure gauge.

The fuel pressure must not fall below 3.0 bar within 10 minutes.

If the fuel pressure falls:
- The check-valve in the fuel pump is faulty, replace fuel pump.

If pressure does not fall:
- The pressure relief valve in the fuel filter malfunctioning, replace the fuel filter.
- Assembly is performed in the reverse of the removal.

Final Procedures
After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Diagnostic Mode 03 - Read DTC Memory
2. If necessary, erase the DTC memory. Diagnostic Mode 04 - Erase DTC Memory
3. If the DTC memory was erased, generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

End of diagnosis