my fuel system has a mind of its own, the fuel pressure just wont hold, it has a few times for me, but outside of that it holds with the car off but drops as soon as i start it. its not the fuel pump, i have curently a walboro 255 currently but have tired my old good pump and it doesnt make a difference, i have brand new fuel lines and fuel hose, theres no kinking in them, the fuel filter has only a few thousand miles on it, and i'm using an adjustable fuel pressure regulator which works just fine if isolated from the system

help me before i burn this thing.

 

Perhaps the injectors are firing too long and/or getting stuck open when they are running.

 

i considered that but the car dies due to lack of fuel pressure, even at 2,000 rpm's.. is it possible for the stock 550's to dump enough fuel to drop fuel pressure by that much?

 

I'm not sure if this is your problem. But bypassing the fuel pump resistor solved my issues...
https://www.rx7club.com/showthread.p...pressure+issue

But my car never died from low pressure? Is your fuel system correctly plumbed? The fuel pressure regulator goes after the injectors.

Pump>Filter>Injectors/Rails>Regulator>Return

If you have an injector stuck open the exhaust would have raw fuel coming out most likely...

 

If you want to bypass the fuel pump relay then unplug the connector to it and jumper Blue/Red to Blue/Green and see how it plays out. The Circuit Opening relay might be problematic due to a poor or nonexistant ground source among other things. The voltage wire to the fuel pump might be of poor quality as well as it can allow the proper voltage to pass through it but at the same time not allow the proper amperage to reach the pump and the amperage level is key. A simple rewiring would solve this possible issue.

 

yes my fuel system is plumbed correctly, and i'll give the fuel pump rewire a shot, thanks!

 

just to see it this was my problem i wired the fuel pump strait to battery and it's doing the same thing. i'm stumped. and ungodly irritated. someone help.

 

What fuel pressure are you getting? With the vacuum hose to the FPR (factory) disconnected the pressure after the fuel filter should be between 35 to 40 lbs. 64 to 85 lbs. before the filter and 28 lbs. after the filter when everything is connected properly.



EDIT: Does you car have the fuel pump relay and resistor? If so its easy to bypass as all you need to do is remove the plug to the relay and jumper the Blue/Red wires to the Blue wires.

 

well im running an adjustable fpr, and its set at 30 PSI and holds until i try to start the car, then it jumps around between 10-20 psi or so, and no i've bypassed the factory wiring(just for trying to figure this out) and i've wired the fuel pump strait to battery. i can't even fathom what could be causing this. could it be my FPR is really just junk? its new, it has worked, but something keeps failing and i cant figure it out. is there any way it would work properly unless fuel was flowing?

 

Does your FPR have a vacuum hose connected to it much like the stock unit?

 

yes

 

Is it connected to the same place as the factory unit? Do you still have the pressure control solenoid hooked up? I believe the pressure control solenoid affects the pressure for the first 50 seconds or so after a hot start. Is your fuel pressure changing during just this 50 second time period or afterwards.

 

no just strait to vaccum, and im not sure if it's where the original line went or not. all emissions have been removed. the car won't even run for that long as soon as the car starts pressure begins to fall, it might run for 10 seconds with me feathering the throttle.

 

I believe the way it works is when deleting emissions you're supposed to see how the car operates w/o the pressure control solenoid and if its removal doesn't affect the car in an adverse way then you can remove it. Don't know if you did this or when the current problem you have occured relative to when the emissions were removed. I believe the vacuum provided by the pressure control solenoid was not constant vacuum.

https://www.rx7club.com/search.php?searchid=9020098

 

i picked up a TII swap that came in peices and the emmisions rack wasnt part of it. but the car can with this fuel system n/a and has run on it with the TII motor, but it changed it's mind on continuing to do so.

 

Just for the heck of it why don't you cap off the vacuum hose connected to the regulator and see what happens related to the fuel pressure you would then see.

 

i'll give it a shot tomorrow

 

If that doesn't work then try a different vacuum source.

 

doh

 

are you 100% certain it isnt an injector going to full flow and emptying the rails?
have you tried removing the rails,, and wire tying the injectors into it and seeing what happens when you crank?
( with the ignition coils unplugged from harness )

PS-- have you changed your fuel filter recently,, i would !!

 

just removing the vacuum line made it run like crap, different vacuum didn't help, the fuel filter has ~6000 miles on it. i havnt tried testing the injectors in that manner, but even if stuck open, i don't believe the stock 550's should be capable of causing such a drastic drop in f/p..worth a shot checkign though i suppose..

 

im sure u removed the stock fule pressure reculator from your secondari fuel rail right...... and replaced with either a banjo bolt or what ever method......

 

haha yes stock fpr is removed

 

I don't see which FPR you're using (Aeromotive, AEM, SX, etc)? Do you have a pic of the regulator installed?

 

Use the Vacuum nipple on the lower manifold,around the Primary injectors,It points to the Firewall.
That nipple is the Primary injector bleed and is a good source of Vacuum to operate the aftermarket FPR.
Note: I have mine hooked up there,I also have NO stock FPR or Pulsation dampener on the rail,as they are all plumbed with aftermarket hoses.