TPITuned Port Injection discussion and questions. LB9 and L98 tech, porting, tuning, and bolt-on aftermarket products.
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fuel pump replaced, but still had problems. We put a guage on the fuel rail and drove it... pressure dropped to about 20 psi above 2500 rpm or when pedal was floored. Now, a new regulator, but still not holding pressure. If we pinch the return line, pressure goes up to over 80psi. Otherwise, we still see low pressure at revs. Mechanic is stumped. Is there a vacuum line to the FPR? If so, what does it do?
any ideas otherwise... please?!
__________________ original, but recently rebuilt 305 TPI flat top pistons 1.94" intake stock heads Comp 256 cam Custome 4000rpm T conveter Edelbrock TES headers with 3" Edelbrock cat back 700-R4 manual shift reverse pattern 3.23 10 bolt rear 16" 20 Slots w/255 BFG G-Force
yes there is suppose to be a vacuum hose that goes to the fuel pump regulator there has to be some type of input to change the output of the regulator. If i remember correctly its on the very top of the regulator at least on my 87 gta 5.7
He figured out the vacuum, I'm sure. That was my question... but I am starting to wonder...
The shop installed a Mallory adjustable FPR. This was their answer to the dropping fuel pressure problem, after they put in a new spring & diaphram in the old FPR
They then left the original FPR alone and added the Mallory FPR to the return line. It seemed to work at first, but out on the street in was back to the same old problem... the car will not accelerate past 2500 rpm or so... sometimes it will rev to 3k. When it falls down at 2500 rpm or so, nothing will let it gain revs. If the pedal is depressed or even floored, not much seems to happen, just bogs and goes nowhere. In park or neutral, it will rev right up to 4k+, no problem, no hesitation.
I just got the car back for the weekend... it is actually drivable. I still have rented a pressure tester. I will put it back on and drive it, but I know I will see the pressure drop at aroung 2500 rpm... it drops to about 20, especially when it starts to bog... flooring it just make it worse.
Can this possible have anything to do with a new transmission installed with a 4k converter?
We are all at a lose at to what is causing the fuel pressure to drop... an open injector, I guess, but would that make it bog down and fall on its face?
__________________ original, but recently rebuilt 305 TPI flat top pistons 1.94" intake stock heads Comp 256 cam Custome 4000rpm T conveter Edelbrock TES headers with 3" Edelbrock cat back 700-R4 manual shift reverse pattern 3.23 10 bolt rear 16" 20 Slots w/255 BFG G-Force
Last edited by suh_wheat_86305; 07-11-2009 at 06:12 PM.
Well, adding the second regulator was wrong IMO. Did they change the fuel filter? Maybe they left the diaphragm out of the main regulator and depended upon the secondary regulator to do the work. Perhaps the new regulator has now failed. The fuel pump should be able to supply 8 injectors stuck wide open so 1 wouldn't be a problem for it.
__________________ In the land of the blind, he who has one eye is king.
Well, adding the second regulator was wrong IMO. Did they change the fuel filter? Maybe they left the diaphragm out of the main regulator and depended upon the secondary regulator to do the work. Perhaps the new regulator has now failed. The fuel pump should be able to supply 8 injectors stuck wide open so 1 wouldn't be a problem for it.
RUN AWAY FAST 
