Possible Fuel problem?


Jun 29, 2005
Ok, I tried searching through the 5.0 tech section but couldn't really get too straight of an answer.

My current fuel system includes a 255 in tank, BBK Adjustable FPR, 42# injectors, and all the lines and everything else is how it came on a stock 92 GT.

I've dyno'd it with my current setup and have a tune for it.
I've got an SCT flip chip, one motor tune, one for a 75 shot, and one for a 125 shot(dry).
Have a n.o.s. 5115 kit, with window switch, bottleheater, and fuel pressure safety.

Now to my problem, the car was running on 24# injectors on my 75 shot last year making around 360 at the wheels.
Was having no problems with it whatsoever. I made the swap to 42#r's so I could get the fuel there for a larger shot because I was kind of pushing those 24's.
Got a new set and maf and installed then tuned.
Car showed a nice air fuel ratio of 11.8:1 all the way to redline.

Now, i finally get my rear end done so I can launch nice and hard on the juice.
I bring it to the track and have it on my 125 shot tune, rev to 5k and dump the clutch.
First and second both pull very hard.
Third does as well but near the top of the gear it seems like it stops spraying completely.
Fourth, it isn't even spraying.
End up trapping around 115(i trap 113 on the motor)

Now to my question, because i'm going through the gears and not just one gear like on the dyno, could it be possible my fuel pressure is staggering in the higher longer gears?
I don't have a wideband to monitor this in car during the run, but it's definatly not spraying at the top of third and fourth.
I do have the stock fuel rails and I hear theyre only good for around 400-450 crank hp and im making almost 500 at the crank.
(425+ at the wheels on the juice)
I hear the 94/95 fuel rails are a little better, would making the swap fix my little issue?
Don't really have the cash to go out a wideband at the moment(which I do want eventually)nor do I have the cash to spend on a full fuel system like something from Aeromotive.
Need help!!!
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New Member
Mar 19, 2006
What have you done with the stock fuel filter? Has it been changed latley?
It seems you have plenty of pump and injector. but you my be restricted at the filter, (inline above rear axle)

as much as you think it is a fuel problem it may be a no2 problem also. Check the window switch,also check vacume at the regulator.


Jun 29, 2005
That track night was actually before the window switch, ended up picking that up recently.
Was using a microswitch before.

Fuel filter was recently changed, just a napa gold filter.
The nitrous is working as it should when I have it sitting in the driveway.
Guess i'll recheck the vac line heading to the regulator though.

But you really don't think it's the stock rails at all?


Jun 29, 2005
Line doesnt look crimped or any cuts in it.
Kind of curious to try and just bypass the fuel pressure safety switch.
Just because, it was running fine before on the 24's and I am running less pressure than I was last year because im running a bigger injector.
So, maybe the adjustment on the fp-safety is off?
Don't have a wideband so, i'd be a little scared to do this.
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