I have been fighting fuel pressure issues for a few months.... I think i am cursed by the fuel pressure gods...

little background - c5 Corvette, Converted fuel system to the 97/8 with return on the rail, LPE 255lph Fuel pump, Adjustible regulator set at 58psi and boost referenced. Stock ATI kit - running 7-8psi, jsut over 500 rwhp. NO BAP.

ok, So - the car was running great with no fuel pressure issues for just about a YEAR on this setup - I DD this car, so it has been about 10k on the clock.

I already replaced the pump and i was seeing a drop in pressure at 2psi right around 3500 rpm, it would drop 10psi instantly if i jumped on it... I chalked it up to a bad pump and just put another one in with a new filter........SAME PROBLEM..... I still am DD'ing the car, and noticed that i dont even have to be in boost to loose pressure - right around 4-4.5k it will start gradually dropping pressure when under 10in of vaccum... there are only 42psi injectors in there, and the car is completly stock outside of the procharger - so without seeing any boost - how could i be loosing pressure? There shouldnt really be any much drawl on the pump.

I checked voltage (still running stock wiring) at the pump at idle and it is around 13v, dropping to 12.9-ish if i rev it up.

The car has been running fine for a year - so i dont really think it could be anything with the feed line or rail, but what else could it be? Maybe a weak altenator? It reads high 13's, low 14's at idle.

I have a 8 gauge wire already run from the battery to the pump area, just never hooked it up as the car was running fine - Not convinced that hooking this up will really do anything - as i have read that running the pump at a higher voltage will increase the heat in the fuel lines - being a DD and about an hour drive either way - i dont want to put any more stress on the pump then it already has.

Any ideas here? I am pulling my hair out - It cannot be the pump at this point.

Thanks!

 

It could possibly be an issue with your gauge I have seen that a few times do you have a mechanical one you can add to the rails? And the hot wire should be run from the back of the alt. and it will help it may not be the issue but it will help the pump keep up.

Nate

 

I have checked with the Manual gauge and it reads the same.

Some people do it from the alt, others from the battery - what would the difference be?

 

better voltage right off the alt.

Nate

 

if the pump is reading 13v off the factory wiring, why would i be loosing pressure under normal driving?

I understand the higher voltage from the altenator will "boost" the pump a little, but this will also increase the heat generated by the pump (i imagine).... I will go this route if needed, but dont see how that would help this situation.

 

Any other suggestions?

This is really driving me crazy.....

 

Not sure if you will have this on your car, but there is a Y line on the return as it goes back to the tank on my car. Had the same problem. Turns out there is a one-way orifice in one of the the lines. If it gets clogged or for whatever reason stops working, then you will have the problem you are describing. BTW.. it is a PITA to get to. Right by the tank above the fuel lines going into the tank on the drivers side.

 

The Y is on the feed line, it feeds the pass side tank to "power" the pass pump to keep the drivers side tank full..... I believe the return goes directly into the drivers side tank.

I would think that if the Y portion was blocked (going to the pass tank) that you would actually hold pressure better, as there would be NO loss of volume going to the pass pump.

I was thinking about that Y and wondering it that could be causing any issues... Did you just replace it or unclog it?

I have also been toying with the idea of moving the Y to the return side to power the pass pump..... so you would have all pressure going to the feed. just not sure if there is enough pressure to power it.

 

i just ended up replacing it.

 

Thanks..

I am checking with my tuner to see if they have one laying around....

 

Anyone else?

 

I think I have the same problem as you 3tenths, I see 60 at idle and about 50-52 psi under full boost and I have only had my car back for about a 1 1/2 months now/900 miles. This really sucks I hope there is someone in here who can come forth and give us the answer...PLEASE

 

50-52 is kinda normal with a returnless system at full boost.... I am having pressure loss when NOT in boost, and i have a return at the rail system...

I dont know what is going on.