ANSWERS TO YOUR BURNING DIESEL QUESTIONS

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Hi again, Jim,

It is Matthew from Australia. I have been having issues with my Optimiser surging at times. I’m not sure if this is the problem, but I have found that my electric fuel lift pump has failed for the second time in five months!

The pump offered here locally is an Airtex brand

(part number: E3158) with a pressure rating of 10 to 14 psi, as indicated on the side of the pump. Have you heard of the continual problems of this pump, and do you know of a better/more reliable brand to replace this?

Could you also tell me what the minimal fuel pressure (from the lift pump) is required for the mechanical fuel pump on my engine? I might even source a lesser-pressure-rated pump. Thanks for any assistance with this.

Regards, Matthew

Matthew,

Most stock electric fuel lift pumps used by the 6.5L diesel deliver approximately 4 to 7 psi, but that pressure can drop to as low as about 2 psi during a hard acceleration. This is normal. Most people discover a problem with fuel pressure when trying to pass, merge at freeway speeds or pull grades with a load.

Generally, the factory pump will last a long time, but the oil pressure switch (which powers the lift pump when the engine is running in the 1994–1995 models) can be more problematic. In the 1996+ systems, power for the electric fuel lift pump originates primarily in the vehicle ECM and related relay, which makes lift pump operation somewhat more reliable.

So, I recommend a genuine GM factory electric fuel lift pump—and you need to ensure the lift pump is receiving power when the engine is running (oil pressure is above about 7 psi). Good luck.