fuel pump losing prime/corvette style filter

[ccobra70]

I started to tune the car with the fast tuner and about every 1/2 mile the pump gets louder and louder and starts to lose prime, we stop the car turn the key off and on and you can hear it re prime (lound at first sec then gets fuel and quiet down) re start the car and runs again for 1/2 mile then starts over.
out of the tank I have a walbro pump then a corvette filter single in duel out one goes to the motor driver fuel rail then a hose connects to the other fuel rail and a block off at the back of the pass. rail. out of the other side of filter it returns to the tank at the back of the car. does anyone know if I have something wrong.
should the pump be pulling out of the filter ( out of tank filter first then pump) I dont know???
I dont think its blockage in tank or why can I stop and key re prime??

[CarlC]

So it's an external pump? How much fuel in the tank? Is there a fuel filter sock? Was the pump run at all without fuel? Does the fuel pressure slowly degrade to zero/almost zero?

[ccobra70]

yes its a external pump, tank has plenty fuel, there is a sock inside the tank, has not been run without fuel in tank but it sounds like its running dry (without fuel) when it loses its prime, and yes when you turn the key on it primes and it has pressure but as you drive the pressure slowly goes down and the pump slowly becomes louder, till the car wont run any longer until you hit the key off and on and reprime.

[MrForce]

Is your cap vented? Try with the cap off...

[JRouche]

How far below the tank is your pump?

I have a 20 gallon aluminum fuel cell with a small sump at the rear of the tank. My supply line drops about 2-3" below the bottom of the tank then into a fram HPG1 filter then to the pump then to another fram HPG1 filter. So if there is any amount of fuel in the tank, lets say any amount that is usable, enough to at least cover the bottom of the tank the filters and pump are always under fuel. Positive head pressure for the pump.

I may rethink my filter setup. Might go with a 100 micron for the supply to the pump and keep the 10 micron after the pump if I see any issues. I plumbed this setup before I knew much about what was needed, still dont know much :)

I went with the frams because they are servicable (I like) and inexpensive (I like) and have a fairly large filter area. And they will handle the pressure. But I dont think a 10 micron filter is need for the pump supply.

If you have a sock or some other type of in tank filter you might think about removing it and going with an external pre-pump filter that is easier to service. If you have the space. And if the pump is at the same level as the bottom of the tank maybe lowering it 2 or so inches to make sure it has as much head pressure as possible. Keep some cavitation down.

But really, the pumps are usually able to keep up with the demand of the regulator (pump, 100+psi, regulator, 50- psi) even under cavitation, found that out when I ran out of gas. But the cavitation will heat the pump up and shorten its life. JR

[JRouche]

Is your cap vented? Try with the cap off...

Very good point!! Need to let the air in.

Its a good troubleshooting point not just a build point.

Cobra, you didnt say the engine was running poorly, just that you heard the fuel pump laboring, which is kinda cool, I couldnt hear my pump if I had to.

So that sounds like the pump is still able to supply the engine with the fuel it needs but the pump is kinda like what? Sucking air like before its primed and has load pressure. I know the sound you are talking about. Like when you turn the key to on and you hear the pump pressurize the lines then it gets quiet once the lines are up to pressure.

But you hear it lose that pressurized line sounds and it sounds like its trying to pressure up.

So yeah, a sealed tank might mimic that blocked fuel line sound. If the pump is trying to pull a vacuum on the tank it will struggle. But you might have some obvious signs of a collapsed tank also, unless there is just enough bleed air to keep that from happening.

But, prolly not. If the pump has fluid to draw from, even if it has to draw harder because of a sealed tank it will still sound like the lines are pressurized, becaue they will be, the lines will be full of fuel, no air. The pump might sound labored, but not the same sound of a pump that is trying to fill and pressurize the output line.

Sounds like a fuel delivery issue to the pump. And that sucks cause it means getting to the sock covered supply line. Tank work :( JR

[ccobra70]

wow thanks everone who replied lots of good info, I did figure it out the shop that put in the filter put it in backwards the filter has 2 lines on one side and a single line on the other side, the single line out goes to motor the other side one is return the other feed, I also learned that its not a 99 up vett filter its a s-10 2.2 flex fuel, filter, which are very simuliar both are internal regulated at 55 to 60 psi and the return, feed lines are flipped. but I think I will add a pre filter to the pump like yall suggested, car runs alot better now, and I really appreciate the responses dont know how we got along before internet!!