Engine/Transmission (1994 - 1998) Fluctuating Fuel Pressure & Low Power

[qwk2sell]

Hi to all! I’m a new member to TDR... I’ve been trying to solve a low power problem. I’ve read many, many past posts regarding low or fluctuating fuel pressure on the 12-valve diesels. I checked my pressure at the fuel filter inlet using a banjo fitting & pressure gauge. My pressure varies from 20+- to 60+- lbs and will bounce the gauge needle at idle & open throttle. I’ve read that others have encountered the same. Just a little background, I’ve owned the ’96 2500 4wd AT since new and just recently noticed a lack of power after towing a larger travel trailer. I’ve changed the overflow valve, fuel filter, heater screen kit, tank pickup filter, fuel tank roll over valve and verified fuel shut off solenoid is working. I also had the reported “vacuum” problem with the fuel tank when opening the cap. Truck has only 97k miles and lift pump & fuel heater changed at 50K under Dodge warranty.



Is it typical to have the pressure fluctuate with the mechanical lift pump?



Thanks in advance!

Geoffrey Greene

 

[NHouse]

You need a snubber in the line to the gauge. The lift pump creates pulses that need to be dampened or you will never get a good reading. I have a gauge in the truck and I used a small brass ball valve for a snubber/shut-off valve. You just have to barely crack it open to get a reading. Just play with it until the needle stops jumping around.



If I remember right anything under ten is considered low and over thirty is high. It will vary with engine temp, load,etc... .





Nick



I didn't notice it was your first post, welcome to the TDR!

 

[Joe G.]

The picture below is how I installed my fuel pressure gauge. The banjo fitting is the imput to the injection pump. Open the needle valve until the gauge just barely works. The pressure spikes from the 12 valve lift pump will eventually wreck a pressure gauge. Idle pressure should be at least 18 PSI. No load pressure should be at least 21 PSI at 2000 RPM.



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[qwk2sell]

Many Thanks to Nick & Joe G... I had read of a line "snubber" in past posts, but wasn't sure what it was or how it is used. I'll put one together and report back my findings.

Thanks again!

Geoffrey Greene