I have the full GDP fuel kit. Just today, I noticed my fuel pressure readings fluctuating pretty erratically. The pressure would hold steady at 24-25# like normal then all of the sudden drop, and erratically shuttle between 18-21# for a minute or so. Then return to normal and hold steady again for a long time before doing this all over again. Never has done this before today!!!

What could this be? Walbro going south? Solenoid? FCA? CP3? I looked and couldn't find or see any fuel leaks.

 

Nobody here has a clue??? I did the search function and turned up nothing. Let me add, that I am running my fuel gauge line strait off the fuel filter canister to the gauge without an isolator.

 

Do you have a isolator in your fuel pressure line...

If so...bingo!

There have been a couple Walbro's that have had a "manufacturing problem". If it is not an isolator...sometimes even though it is a rarity...it could be the pump. GDP will ge tthe pump warenteed ASAP.

 

no matter how tight i get the nut, or how much teflon tape i put on it, my isolator ALWAYS leaks water out of it. you just have to remove the gauge side and fill it back up.

 

He says no isolator...

I would call Richard at GDP and see what he thinks. How old is the filter?

 

ok. that rules that out. howabout if your low on fuel, when the pump starts to cavitate, your fuel press will dip until it picks up some more fuel, then it will spike before the regulator brings it back to normal. ( you cant trust your fuel level gauge with a upgrade drawstraw either.) I have seen this happen at a quarter tank before, but its all talk, i can run it on down to a little below an eighth, when the fuel press drops into the red and stays there for a while.

 

need to use locktite 545 thread sealant on everything that you would normally use teflon tape or any type of pipe sealant on.

 

I noticed today, it mainly does it when 1st cranking the truck and few minutes just after while driving. When I turn the key on, I can hear a distinct and weird sound from the pump that sounds like cavitation, but my tank is at 3/4 full and just filled up 3 days ago. I'm starting with the easy/cheap tricks 1st. 1 red bottle of Iso-Heat, fuel filter, and new relay. The filter has about 15k miles on it. And maybe just got a bad batch of fuel. Also, it seems the pressure drop is related to the grid heater firing at startup, hence the relay may not be sending enough voltage to the pump. The truck and engine does not seem to be running or idling any different than normal, that would indicate air on the suction side as the cause. The gauge point is at the bottom of the filter housing..............pre-filter.

I'll do each separate to see if/what one fixes the problem.

 

I called and talked with Richard and he diagnosed it as most likely to be a bad pump. I may have one of the few/rare "so called" defective units from the 1st run of pumps after the manufacture plant change. I've started a new thread i my search for a possible alternative pump.