I have good fuel psi 13-15, but every once and a while it will drop down to about 5 psi. I can turn the truck off and crank it back and the fuel psi comes back to normal.
Is the lift pump going bad or is it the isolator going to my gauge? Sometimes it's worse when I fill the tank up. I thought it might be sucking air and cavitaing the pump.

 

Might be a dirty filter, but sure sounds like a lift pump to me. Mine was doing the same thing right before I replaced it with the Glacier.

 

I would replcae it, after checking the filter. I have read that the isolator can also case problems.
It is a good idea to keep a spare LP in the truck.

 

I had the same problem for the last week - replaced the lift pump today. It was only about a year old. I put a inline filter before it hopefully to keep stuff out of the pump valves. NAPA requires it for warranty it says on one of their boxes. Hope that doesn't cause me problems.

 

It's the lift pump. Mine did that also, before I went to a FASS. Couldn't understand why the pressure would drop but restarting the engine would get the pressure back, for a few minutes. Dumped that factory LP and never looked back.

Chris

 

I'm installing a Holley Blue this weekend.