I have been noticing a drop in fuel pressure lately on the guage up until a week or so ago. I have a DiProcol pressure guage with an isolator and have had to add anti freeze to the isolator on the guage side on occasion as air is worked out of the system, but that is not the problem now. My fuel pressure has been going to zero after a minute or two after startup. So when I got home from work last night and shut off the engine, I hit the bumpstart to make the pump run. Pressure went to 15 psi and held for 10-15 seconds, then the pump motor revved up and the guage pressure dropped all the way down to zero. I have noticed a slight miss or shudder in the engine last weekend pulling the 5ver. We are going on another trip next weekend and don't want to do any damage to the VP44 (Already had 1 VP44 and 2 Lift pumps put in under warranty). The truck only has 69000 miles on it. Anyone else experience these symptons?

 

Sounds like your lift pump is done for.

That stumble/shudder is your VP telling you that you're hurting it already. I will shine a beacon of light on you though.... before I knew anything about the VP/Lift pump problems I had a lift pump die on me at 88K, I had no fuel pressure gauge so I only knew something was wrong because the truck stumbled at highway speeds with trailer in tow. I ran it that way for 3 weeks because we were on a jobsite about 80 miles from home. My VP made it to 159K after having less than adequate fuel for 3 weeks under load!

I suggest you replace the lift pump and figure out what's going on with your fuel pressure gauge. I have the exact same gauge with isolator and I have never had to refill the gauge side with antifreeze.

 

Thanks Smokindog. Calling the dealer on Monday. The 1st lift pump quit after an oil change and fuel filter change. That time a tow truck had to be called to take it in.

 

With the lift pump revving up like you said, another possibility is you have a fuel line leak before the LP, causing it to pull air instead of fuel.

 

Have not seen any leaks.

 

In the line from the tank to the lift pump it's likely you wouldn't. The fuel system isn't pressurized until after the lift pump, so if you have a leak it will suck air instead of seeping fuel. I'm not sure of the best way to check for leaks in that part of the fuel system, but there are quick-connect fittings at the lift pump and tank you could start with, by making sure they're connected tightly. I always thought of those fittings as sort of hokey, which is one reason I was glad my FASS system came with a whole new fuel line to replace the factory setup. I'm not saying there isn't a chance of lift pump failure, everybody on here knows about stock lift pumps and I went through 2 of them myself before the FASS...but the way you described the pump speeding up it sounds like a big load was lifted from it, like sucking air instead of liquid.