ISM, ISMe, and QSM11 – Operating Fuel Pressure is Low

Symptom Tree  t109

This is symptom tree t109
Cause Correction

Air in the fuel system

Check for air in the fuel system. Refer to Procedure 006-003.


Fuel inlet restriction

Check for fuel inlet restriction. Refer to Procedure 006-020.


In-line check valve(s) is installed backward or has an incorrect part number

Check the in-line check valve(s) for the correct part number. Check the arrow on the check valve(s) for the correct orientation. Refer to the OEM service manual.


Fuel pump pressure regulator is stuck

Check the fuel pump pressure regulator and the high pressure regulator. Refer to Procedure 005-060.


Injector o-rings are damaged or missing

Remove and check the injectors. Replace the injector o-rings. Refer to Procedure 006-026.

Last Modified:  22-Dec-2003