Stock 2002 24 valve dodge 2500 4wd. Replaced block lift pump with another stock style block pump in May. This pump supposedly has bypass valves in it to prevent injection pump failure if the lift pump goes out. According to the specs it should be b/t 10-15 at idle but there is no minimum for WOT. It claimed that the pressure specs would be more like the newer style "in tank" pumps. At idle mine is usually just over 10, under load usually would drop no more than 5. Last night I get in and crank it up and its idleing around 4-5 psi. Thing is it doesnt move much as I accelerate. It normally would drop as I accelerated. At WOT I can get it to drop maybe 1 psi. So I figure I have one of three things wrong.

1. Bad lift pump. AGAIN.
2. Need a new filter. (could a dirty filter cause this?)
3. Bad gauge?

 

try replacing the filter first, then check the gauge

 

How would I check my gauge? It is an Isspro mechanical gauge with a fuel block valve in the engine compartment.

 

Use another guage. It doesnt have to be for fuel - any pressure guage will work.

This is the easiest place to start.

 

Well its not the fuel filter. Ill have to put another gauge on it Monday when I get back too work. This sucks b/c im leaving out here in a couple of hours pulling a 28' stock trailer about 220 miles. Hauling back about 15000 pounds of cattle. Dont have any other truck to take. Ive got fuel pressure and the truck feels like it has power so I should be fine.

 

Could it be that the fuel pressure isolator is leaking? I had mine do the same thing and traced it to the isolater

 

He didnt say if he was using an isolator

 

you don't say if the gauge is electric or mechanical, but i'll bet it's electrical. and i'll bet that's the problem

 

He does say it's mechanical and I'll bet the fuel block vlv is an isolator. It could be he's lost some antifreeze from the isolator to the gauge. Happened to my father in-law. He topped it up and tightened the fittings it's been good for almost 2 years.

 

It is the gauge. We hooked up another gauge and its reading normal. Pulled my mechanical gauge out of the pod and saw a little drop of antifreeze at the fitting. I guess I need to unhook the line at the isolater and make sure the diaphram is pushed the right way and fill up the line again.