Fuel Pump Pressure

[j5ash]

Can anyone tell me what pressure a Walbro 340 is capable of producing ? I only seem to be able to get about 57-58 psi at WOT no matter what I turn the FPR up to. The pump is hotwired. Thanks Jason

 

[Madcat455]

How much boost is it running at WOT??

 

[j5ash]

18-20 psi WOT.

 

[j5ash]

Anybody? Please help, don't want to buy another fuel pump if not needed. Thanks Jason

 

[Clark6]

i recently bought an in the car fuel psi gauge & i have seen it at any where from 61 & 72 psi wot, i read some where the set up at 20psi of boost with vacuum hose off at 42-43 at idle & wot was 60psi was the hot set up. i have 42.5 lb inj. also a hot wired 340. just check to make sure fuel lines arent pinched, new fuel filter, good grounds and no vacuum leaks. oh yeah also once i kept hearing the whirrring noise of the pump over the summer or 2 ago get louder so i replaced the fuel sock & no more probs. since......waycross ehh i live 30 minutes from you i think theres another white -t runnin 7.20 or 7.30s your way, better not pull beside him LOL.

 

[Black Car]

Are you sure your gauge is accurate? What brand is it?
I have seen many less expensive gauges be off from 5-20# over the years.

Here is one way to see what pressure you pump can do.
Jumper the pump to run or just start the car.
Use a pair of pliers (with a rag on the return line-so you don't damage it) and slowly clamp off the rubber return line below the power steerning at the frame. You should see the FP start to raise as soon as you clamp down on the line. I have seen anywhere from 75-90 psi on good pumps.

Gary

 

[j5ash]

Yeah that is what I had always heard, 42-43 vac off and should be at least 60# at WOT. What I didn't know was does the fuel psi rise a certain amount as the boost comes up ( example 1# fuel psi for each psi of boost). The car is just breaking up and popping and sputtering at anything over 10 psi of boost. I can spray alky to it and it runs awesome. It's brand new engine, with only changes being roller cam and rockers, 70mm TB and upper, and LS1 MAF and translator. Could this produce enough extra volume of air to be too much for my 009's? Thanks everyone for your help. Jason

 

[turbofabricator]

I think you need to double check your gauge with a new/known good one. Yes, the Fuel pressure will rise 1:1 with boost. Pull the vacuum hose off while the pump is running to see if your regulator diaphram is leaking fuel. Fuel will come out of the vacuum nipple. Double check your gauge. It might also be a leaking hose intank between the pump and the sending unit. Did you cut off the necked down section of tubing on the sending unit before you installed the splice hose? Did you over torque the hose clamps and caused them to strip out? (very common) If your gauge checks out then I'd drop the tank and pull the sending unit out and look for problems there. Did you use the supplied high pressure EFI rated hose or did you use cheap auto parts store stuff?

 

[87GN_70GS]

The pump relief valve should open at around 100 psi. Like one poster said, test it with no load; with the motor idling turn the fuel regulator up or add compressed air to the fp regulator. You should see 90+ psi (unless the engine stops).

Under load, the pump has a leak...well actually 6 of them. The injectors will bleed off some pump capacity, but a hotwired 340 should have enough to provide a max of 70-75 psi with 009's at 100% DC and 20 psi boost.