I took my car today to national speed in wilmington nc to get tuned, and first thing i want to do is thank the guys there, specially Taylor and Jordan who supported me all the way and try to work with me in any possible way!

eveything was going fine until we started going up on boost levels, the fuel pressure started going down to about 25-30 psi, first it would go up a few psi then it would start dropping. we broke our heads and made a few calls trying to figure out and could not figure anything out anyway. this is a list of the things we did trying to fix it:

after speaking to ryan and shariff @ forged they suggested it might be in the pump assembly,mind you that everything on this setup is brand new from 3-4 months ago but i had to start somewhere

1) pulled the pump out and changed it,didn't fix it

2)pulled back out drilled 2-3 holes like the turbonetics ( maybe it was sucking all the fuel and not refilling the tank fast enough) same thing

3)a month ago i bought and installed a new aeromotive FPR thinking my old one was bad did the same then i figure it would fix after the tunning, so we check that anyways just to make sure and it was brand new like we expected (diafram and spring)

4)check all the lines for leaks and kinks, the were a small kink in the front but after fixing it still nothing no leaks what so ever

5)we did do a test on the fuel pump voltage and it was steady 13.8 then as you started to go up it would also raise by one per each pound of boost 13.9 14.0 14.1 14.2 14.3 14.4 i think was the highest

6)we also changed the vacum lines for leaks and kinks and changed the one for the regulator.

so taylor tuned it to 9psi and were it would not lean out car made
390w/393lbs so i could drive back safe until i can fix this but we did see almost 500 on both on higher boost levels just before we noticed the leaning.


ok the setup is Aps twin tuner kit with upgraded 3.5" downpipes and external wastegates, 750cc, AAM fuel return system (custom made to their exact specifications), walbro 255,cjm fuel rails, built short block with arias 9-1 0.20 over, eagle rods, cometic HG, coated bearings, Arp eveything, aeromotive FPR, utec,xs map sensor,xs boost controller, ngk 6's, AAM 3" true dual, rps clutch & cynergy flywheel.


any suggestions? has anybody faced this problem on a z before? please help!

 

Have they verified that the voltage at the fuel pump is sufficient? Also, what is your fuel pressure at idle with the vacuum reference disconnected? If they increase fuel pressure, do you still get the same drop?

If a.)you replaced the pump b.)the rails and fuel lines are of adequate size, and c.)there are no kinks or leaks anywhere, it would almost have to be electrical.

 

Oh, and check the vacuum line to the regulator for kinks/leaks.

 

pressure test the fuel pump housing for leaks. a leak at the regulator plug or a crack in the plastic would lower the max potential dramatically. you can also try another assembly from another car to see if the problem gets resolved as this would also eliminate the chance of a backed up fuel filter. no need to put the holes in the canister, stock pump assembly with no holes at all will feed a 600rwhp car.

 

yea i forgot that, we did do a test on the fuel pump voltage and it was steady 13.8 then as you started to go up it would also raise by one per each pound of boost 13.9 14.0 14.1 14.2 14.3 14.4 i think was the highest

as for the leaks in the housing we checked as i took off the pump

 

we also changed the vacum lines for leaks and changed the one for the regulator.

 

we did not swap the hole assembly yet, we are thinking about putting a
in-line fuel pump.

 

Well good luck to you, sounds like you are in good hands.

 

Thanks!

also one of my boys had a boosted s2000 and said similar thing was happening to him at about 500whp and wha he did was tap the walbro pressure valve to make it raise pressure on top and said that fixed it for him, what do you guys think about that? plus they modify the 255 for srt-4 the same way all the time cause of similar problem.

 

i think that you are right charles, cause you know how the you have to drill for the return and i remember i drilled wrong then blocked it and drilled correctly the second tim, it has to be that cause it won't do it inmediatly but under boost it does. thanks i think i might even go with a twin pump system from your company, can you give me shout 336-899-9742