stumble with gt500 pumps

[Wicked One]

Just picked up my car from the tuner. On the dyno it ran great and no issues.

Once we started tuning on the street, the car started stumbling when we got on it. Only way it would run good would be if we rolled on the throttle.

The data log was showing fuel spikes as if the computer was panicking and throwing all it had at it and then shut it down etc...

This is on a stock gt500 hat and pumps with dual fpdm's, the tune is for this fuel system.

I need some troubleshooting help, could the fps on the rail be crapping out, one fpdm. Where to start.

Thanks.

 

[07VistaChicago]

You can check the FPDMs by unplugging one, starting car. If it runs (don't drive it) then that one is good. Shutdown car and unplug the other one and replug the other one in. Repeat.

But really, achems razor, it's probably in the tune.

 

[Wicked One]

I just tested the fpdms by idling then unplugging 1 at a time, the fuel pressure dropped, then I plugged it in and it spiked, same for the other one, car stayed running.

Have to wait till monday to talk to the tuner.

here is a quick vid at idle fuel pressure and then with a little gas.

 

[lito]

Why you have 60psi RAP? Your deltaP might be what, 70?

Forgot to add, is this system newly installed? if you had it before, by chance, it worked right until it got tuned?

 

[Wicked One]

A new fuel system. Had a single pump with a bap before.

Gonna have to call the tuner on monday, nothing else I can do now.

Thanks.

 

[Sofakingfast]

I had a FRPS freak out and do that yesterday on the dyno ...

 

[TexasBlownV8]

That's your fuel pressure? Seems a little high! Mine stays around 40, with the gt500 pumps.

Don't remember if you have an auto or manual, but if trying to tune torque management via the 'default methods', you'll probably run into problems.

 

[michael.konor]

I'd go back to the tune. My tuner had to tweak my starting and low speed low offs. The way he explained it to me is that my low speed throttle position was tipping the A/F ratios lean and rich right at the 14.7 A/F ratio, along with the difference of "loading" on the street vs. dyno. This was causing my stumbles on the street, while not having it happen at all on the dyno.

He adjusted the tables and I haven't had a problem since.

 

[Wicked One]

Went for 2 test drives today and an assesment of my fuel pressure gauge. My fp sending unit crapped out. Replaced the gauge and sender and now have a more reasonable reading of 40psi at idle and goes to maybe 50 at rev.
First test drive was the same thing. But the second it seemed much better. Traction was hard to find, but hopefully the computer is relearning. Will check again in a bit where I can get on it more.

Fingers crossed.


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[ford20]

Best of luck with it Gregg

 

[06RFSTANG]

Hope you get it worked out Gregg..you should have taken a ride up my way to check the car out

 

[Wicked One]

Thanks guys. Took some more runs. Seems better but still chokes out going around left hand turns. The pressure doesn't drop though. Will see what my tuner says tomorrow.

My car is stick. Soon to have a 6060.
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[1BADHRSE]

Soon to have a 6060.

STOP IT..... lol You keeping the 8.8 rear?

 

[Wicked One]

Yes I am. Why Joseph. Do you want it? I am putting down over 650 but less than 710. So I don't know if it will last.

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[1BADHRSE]

Yes I am. Why Joseph. Do you want it? I am putting down over 650 but less than 710. So I don't know if it will last.

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Just trying to decide for myself what to do for a rear... Right now I have an issue with my ring and pinion. 300 to just replace with 3.73s ditching the 4.10s or move up to a 9''. idk what to do or what i have the funds for....

 

[Wicked One]

Small update. car is running much better now, might have had to relearn some things.
At a half tank of fuel, then the gauge gets all screwy and drops to empty, never did that before.

Also, when the car sputters, the fuel pressure does not drop but the A/F is 17.5.

Still looking into some things, but will be going back to the tuner this week. I have enough fuel hats here to test out.
1- stock gt
2- stock gt500
1 gt500 modded with aeromotive 340's

all do/did the same.

On another note, driving with the new twin disk clutch is fun, gonna take some getting used to.

 

[1BADHRSE]

Once I hit half a tank mine goes crazy also that's why I kept that spare tank in the trunk.

 

[lito]

That is not a pump issue. Hope you get it solved. Please, let us know how it went.

 

[Wicked One]

I definitely know now it is not mechanical. I took the complete fuel pump and both fpdms from my gt500 and the same thing is happening.

Gonna talk to my tuner again in the am and try and get it on the dyno.

I am going to do some data logging tomorrow and see if anyone can understand what is going on.

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[rford426]

Fire your tuner and just get with LITO...Im in the process of doing this...Once I get my fucking wideband working with SCT (if I ever do) Im getting a couple tunes from lito and im sure many of my small problems now will go away!~