Been a member for awhile but usually don't post...but need help. After installing the fuel system I purchased from RX7store.net (new pump, FPR, and 1600cc inj) I am running extremely lean (15 to 1 A/F ratio) once I start to boost. The fuel pressure is set to 43 lbs and it climbs to 60 lbs until about 4-5K rpms and then the fuel pressure drops back down to 43 lbs. The car was running terrific but the high A/F is scarring me. I have stock turbos (non-seq) with the wastegate wide open, and am using the Power FC. When I dyno'ed before the fuel system I had a A/F ratio of 11.4 to 1 all the way to 8K rpms. We did check vacume and that is not the problem.

Mike B

 

Sounds to me like the pump isn't keeping up with the demand.

I would check the wiring of your pump. I would also check that you reinstalled the ground wire when you did the fuel pump swap. I am pretty sure there's a small ground wire that you bolt down under one of the bolts near the fuel pump.... check that too.

If your wiring is good and putting the stock pump back in fixes it, I'd suspect a bad pump.

 

Agreed, it sounds like a fuel pump problem.

 

3rd it

 

I posted another problem I was having am now think the two may be related. This is a link:

https://www.rx7club.com/showthread.p...hreadid=324170

It won't start until several times or when it gets warm.

I'm going to check the ground on the fuel pump first, then switch out the pump, with my friends stock pump from his 3rd Gen. We are mounting my camcorder to the strut bar and running the video to my kenwood TV in my dash..(this should be interesting). That way we can see if the fuel pressure is dropping at boost or not. I barrowed another Aeromotive FPR from another 3rd Gen and were gonna try to swap that if all else fails.

Thanks for the help,
Mike B

 

I, actually, would start with the FPR. You need to check opperation. It sounds too strange that the fuel pressure would just drop to the vaccume pressure setting. Also, check the duty cycle of the new injectors (i.e 1600).

 

We did start with the FPR and it did the same thing. Then we swapped the brand new RX7store.net competion fuel pump with the stock one. And guess what it fixed it....To double check we are taking it to the dyno tomarrow. I am sure Jason will swap it out with new one since I just got it. The strange part is that other FD owner with same fuel system is having same problem. Thanks for all your help!

Mike B

 

Forgot to mention it also solved my problem with it not starting when cold! To birds with one stone!

 

Sorry to bring this back from the dead, but I couldn't pm the OP. When this happened, did the pressure drop back all of a sudden, almost like a switch got thrown, or did it slowly bleed back?

I'm having this exact same problem and my fuel pressure drops back down very suddenly. Does this sound like it might be my fuel pump going out?

Thanks.

 

You might start by checking the voltage at the fuel pump, if you haven't already.

Search on fuel pump rewire, and you will find the info.

 

I bet the voltage at the pump isn't 13 + volts like it should be. See me thread in this section.

 

Sounds like a voltage drop on the second stage. Search for fuel pump rewires and i bet you'll find your culprit.

 

Thanks, I'll check that tomorrow. I think it might be more than just that because I was checking my fp gauge, and I get get stable fuel pressure above 43 psi. Once it gets to 43, the needle will start bouncing all over the place. This is with the supra fuel pump.

 

bencb44 i was having the same problem on the dyno with my supra pump. We rewired the pump and it fixed the issue

 

Yeah, I ended up going with dual walbro's and wiring them straight from the battery too. This was suggested by my tuner. Turns out it's pretty big overkill, but I don't mind that on my pumps.