Fuel Gauge Sender: Service Precautions

Before Opening High Pressure Fuel Injection System

For safety reasons, if the battery is not disconnected, fuse - 28 - from the Fuel Pump (FP) Control Module (J538 ) must be removed before opening fuel system. Otherwise, the fuel pump will be activated by the driver's door contact switch.





• The fuse is located in the fuse carrier in the instrument panel.

• By removing fuse - 28 -, the voltage supply to " terminal 30" for the Fuel Pump (FP) Control Module ( J538) is interrupted.

CAUTION!
The fuel injection system is divided into a high pressure section (maximum approximately 110 bar) and a low pressure system (approximately 6 bar).

Before opening high pressure parts, e.g. removing high pressure pump, fuel rail, fuel injectors, fuel pipes or Fuel Pressure Sensor (G247) (G247), fuel pressure in high pressure area must be reduced to a residual pressure of approximately 6 bar. The procedure for this is as follows.

High fuel pressure, reducing

Special tools, testers and auxiliary items required

• Assembly tool (T10118)

- Remove electrical connector - 2 - from Fuel Pressure Regulator Valve (N276) using the Assembly Tool (T10118).





- Allow engine to idle approximately 10 seconds.

• By removing the electrical connector from the Fuel Pressure Regulator Valve (N276) in idle, the fuel pressure is reduced from approximately 50 bar to approximately 6 bar.

• The decreasing fuel pressure can be decreased if a Vehicle Diagnosis and Service Syst. (VAS 5052) is connected and engine control module is selected. And select display group 140 under " Read measured value block" function.

• Fuel pressure (actual value) is shown in display field 3.

- Switch off ignition.

CAUTION!
The fuel lines will continue to be filled with fuel, but will no longer be under high pressure. To open fuel system, wear protective eyewear and clothing to prevent injuries and contact with skin.

Before opening the high pressure system, place a cloth around the connection.

- After reducing high pressure, high pressure system can be opened. To do this, place a clean cloth around connection to reduce residual pressure in system to approximately 7 bar. Escaping fuel must be absorbed.

• If the high pressure line is not opened immediately, the fuel pressure can increase slightly.

- Connector Vehicle Diagnosis and Service Syst. ( VAS 5052) and generate the readiness code in the engine control module in "Guided Fault Finding" operating mode.