Engine/Transmission (1998.5 - 2002) fp pressure loss on start up

[BHitt]

My 99 2500 has a l/p on the frame as well as the one on the engine. when i start it up I have 18 psi on the gauge. With in about 30 seconds the psi drops to about 12 psi. I have changed the so called unloader valve and it still acted the same. Has anybody had this problem before if so what is the cure??

 

[AKAMAC]

It may be your gauge or where you are getting the pressure value from. Are you checking at the vp or the filter? Check the voltage to the pump, you may have a bad connection. Get a manual gauge and install some fittings from a 00~02 so you can spot check if you see a problem. BTW, 12 PSI is not too bad.

 

[BHitt]

I'm getting psi at the f/f before it goes the the inj. pump. Problem is it drops to about 6 psi on hard acceleration. Thanx for your help . I installed the gauge per the instructions recieved. It is not a manual gauge.

 

[AKAMAC]

Are you running both bumps without a relay? If you are then you may have a voltage drop to one of the pumps.

 

[BHitt]

Yes there is a relay involved in both pumps. This was a B D setup installed by Mac's Trk Perf in Ft Worth. They are pretty good about this kinda stuff. I talked to them just recently and they seem to think maybe one of those lift pumps may be going out. If that proves to be the case a new Fass system is next . I am so tired of all this f/pl/p B. S. on one of this best trucks on the road. Thanx for your help!