Before Opening High Pressure Fuel Injection System
Before Opening High Pressure Fuel Injection System
• The fuel injection system is separated into a high-pressure section (max. approximately 120 bar) and a low-pressure section (approximately 6 bar).
• Before a component in the fuel injection system high pressure area is remove, the fuel pressure must be definitely reduced to a residual pressure of approximately 6 bar, as described in the following.
Special tools, testers and auxiliary items required
• Vehicle Diagnostic, Testing, and Information System (VAS 5051B)
Procedure
- Start engine and run at idle speed.
- Connect Vehicle Diagnostic, Testing, and Information System (VAS 5051B).
Display on (VAS 5051B):
- Click on the Vehicle Self-Diagnosis button.
Display on (VAS 5051B):
- In selection - 1 -, press vehicle system "01 - Engine electronics".
- Wait until next display appears.
Display on (VAS 5051B):
1 Control module identification of engine control module (ECM)
- Click on -> button.
Display on (VAS 5051B):
1 Selection of diagnostic functions
- In selection - 1 -, click on the diagnostic function "08 - Read measuring value block".
Display on (VAS 5051B):
- In button field - 2 -, press buttons 1 4 0 for "display group 140" and confirm entry by pressing Q button.
Display on (VAS 5051B):
- Check display for fuel pressure in fuel rail in display field - 3 -.
Example:
3 40.63 bar
- Disconnect electrical connector - arrow - at Fuel Metering Valve 2 (N402) on left high pressure pump.
- Disconnect electrical connector - arrow - at Fuel Metering Valve 2 (N290) on right high pressure pump.
Display on (VAS 5051B):
- Check indication in display field - 3 -:
• Fuel pressure in fuel rail must sink to approximately 6 bar.
- Switch off ignition.
The fuel rail will continue to be filled with fuel, but it will no longer be under high pressure.
Now components or lines can be opened. Lay a clean cloth around the connection points and collect the escaping fuel.
Final procedures
- Reconnect electrical harness connectors.
Faults are saved in ECM when electrical connectors are disconnected:
- Connect Vehicle Diagnostic, Testing, and Information System (VAS 5051B).
- Start "Guided Functions" operating mode.
- Generate readiness code in ECM.