Engine/Transmission (1998.5 - 2002) VP44 Question

[DFerverda]

I thought i lost my glacier diesel walbro lift pump.
Fuel pressure dropped to 12 lbs, i changed the filter , it stayed the same. Next few days the pressure dropped to 10 then to 8 I ordered a new lp. I checked the bypass valve (inline by pump)to be sure it was not stuck open, it was fine. I also cleaned the pre filter (strainer) before the pump it was clean and clear.

Pressure ended up at 3 then 1 i parked the truck. Tonight the pump showed up and i installed it. Started the truck and no fuel pressure. I checked the electrical system working fine had 12. 4 volts to the pump. I restricted the bypass and got it up to 5 lbs on gauge. I was thinking air in the lines but truck ran fine. I have a mechanical pressure gauge with vulcan isolator, i bled it and still 5 lbs.

My question is, the bypass in the vp44, could it be stuck open? I ran out of time tonight to look how much fuel is being returned.
I have a drawstraw and 1/2 inch lines from the 392 lp (frame mounted beside the tank) to a 2002 fuel filter and all the way to the vp.
Any ideas ?
Dirk

 

[BDaugherty]

I don't think that the return on the VP44 could stick open enough to bleed off all the flow that the Walbro is capable of. How does the Walbro sound? Could it be cavitating? Could you have a restriction in the line going to your gauge? Could you test your fuel pressure another way to be sure? Also, try taking the return line loose from the IP and running it into a light colored bucket. Make sure that the end of the return is under the surface of the diesel in the bucket. What does the return flow look like? Does it have air bubbles in it? Is it a very weak trickle? If you're getting good return flow with no bubbles and the Walbro sounds "good", check and double check fuel pressure readings.

 

[fox]

How much fuel in the tank?

With the draw straw I had to keep the tank above about 1/4-3/8 or it would suck air.

 

[JLandry]

Dirk,



Before you go any further, I'd go to the auto parts store and buy a fuel pressure test gauge kit and *verify* you really have no (or low) fuel pressure. It's like getting a second opinion.



Such a gauge should cost $30 or less.



Good luck,



John L.

 

[DFerverda]

Thanks for the reply's BD andJohn you hit the nail, I should have done that first, but the order things happened, it was like a dying carter lp. It ended up being the isolator the compression fitting on the top must have gotten snagged on something and it pinched the flow to the fp gauge.
I put the test gauge on post filter and got 22 lbs, i guess i can take out a shim or 2.

I will test the old walbro pump, I bet it fine, at least i have a new backup, but from this point on when there is trouble, the gauge will come out first... .
Thanks
Dirk