- 6.5L Fuel Lift Pump -
For all GM and Chevy 6.5 diesels turbo and non-turbo from 1992 through 2005.
The most common symptoms of lift pump failure are slightly harder starting and low power.
This pump is located underneath the driver's seat area inside of the frame rail and should produce around 4 PSI of pressure to the injection pump. You should be able to hear and feel this pump running. Another method to verify the pump's operation is to open the fuel filter water drain in the engine compartment with the engine running. If fuel sprays from the end of the hose and the truck continues to run, the pump is still working. If the truck dies, you may need a new pump.
Continuing to operate with a failed diesel lift pump causes overheating and eventual failure of the injection pump and PMD (if you have not graduated to a remote mount PMD).
Before replacing a diesel fuel lift pump that is not working, be sure to check for 12 volts at it's terminals with the truck running. Use paperclips to back probe the connection instead of unplugging the pump since an unloaded circuit will give a false reading. If 12 volts is not present, the problem may lie with the oil pressure switch located at the back of the left cylinder head. The pump receives power through this switch with the engine running, but through a separate relay with the engine cranking.