For some reason I still don't have enough fuel. Running lean. - MustangForums.com



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Old 05-07-2013, 03:34 PM   #1
ToxicReaper7
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Default For some reason I still don't have enough fuel. Running lean.

I just installed the Ford racing dual fuel pump and harness because I was running lean with the stock pump,boost a pump and 47pound injectors. Now with the new gt500 fuel pump, my tuner is telling me im still running lean over 5500rpm's at 400rwhp. Kinda low since the gt500 is running 550hp stock with the same pump. Im running out of idea's here. What could possibly cause my car to lean with only 400rwhp? Anybody had this issue before? Please help. Thank you guys!!!!!!!!

2006 mustang gt automatic with the on3performence 70mm turbo kit, 4:10's, 47pnds injectors, gt500 dual fuel pumps, and lots of other suspension goodies.
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Old 05-07-2013, 04:08 PM   #2
2005Redfire6
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You sure your tuner knows what hes doing?
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Old 05-07-2013, 07:32 PM   #3
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What are the fpdc (fuel pump duty cycle) numbers showing? Good GT500 pumps should not be going lean at that low power level.
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Old 05-07-2013, 09:10 PM   #4
SpartaPerformance
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Stock fuel system is good for 450BHP, there is NO WAY GT500 pumps and 47lb injectors are not enough for 400RWHP. Go elsewhere.
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Old 05-08-2013, 08:25 AM   #5
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Originally Posted by SpartaPerformance View Post
Stock fuel system is good for 450BHP, there is NO WAY GT500 pumps and 47lb injectors are not enough for 400RWHP. Go elsewhere.
+1, I think the issue may be with the person tuning the car itself.
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Old 05-08-2013, 10:21 AM   #6
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Originally Posted by 2005Redfire6 View Post
+1, I think the issue may be with the person tuning the car itself.
That or he is just having a problem elsewhere in the system. Who's tuning it? Maybe someone has some experience with them.

Lean could be an air issue just as easily as a fuel issue. Check your maf and all your inlet piping/intercooling piping to make sure you arent sucking in un monitored air somewhere. Check fuel lines. Do you have A/F ratio gauge to see for yourself? How about a fuel pressure gauge to verify it isnt a line issue or somewhere else?

Just throwing out some ideas. Good luck.
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Old 05-08-2013, 02:24 PM   #7
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Originally Posted by TheStigSC View Post
That or he is just having a problem elsewhere in the system. Who's tuning it? Maybe someone has some experience with them.

Lean could be an air issue just as easily as a fuel issue. Check your maf and all your inlet piping/intercooling piping to make sure you arent sucking in un monitored air somewhere. Check fuel lines. Do you have A/F ratio gauge to see for yourself? How about a fuel pressure gauge to verify it isnt a line issue or somewhere else?

Just throwing out some ideas. Good luck.
This is the best advice. But if nothing is apparent after checking these items, its prolly the person tuning.
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Old 05-08-2013, 07:06 PM   #8
moosestang
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Be sure both pumps are running! You wouldn't be the first person to get a bad fuel pump wiring harness or fpdm.
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Old 05-08-2013, 07:19 PM   #9
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I once had a set of GT500 pumps where one of the two pumps all of a sudden went bad. The motor would run until the FPDM's would overheat and then it would lean out (AFR would start climbing 16, 17, 18) and the motor would die. Let it cool off and then it would run fine until the FPDM's got hot again. Nursed it home about 180 miles on I-95 that way.

That is why I asked the OP about fpdc numbers. With both pumps working he should be at 19-21% at idle. A bad pump will double those numbers.

Last edited by jpplaw; 05-08-2013 at 07:28 PM.
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Old 05-08-2013, 08:21 PM   #10
moosestang
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Originally Posted by jpplaw View Post
I once had a set of GT500 pumps where one of the two pumps all of a sudden went bad. The motor would run until the FPDM's would overheat and then it would lean out (AFR would start climbing 16, 17, 18) and the motor would die. Let it cool off and then it would run fine until the FPDM's got hot again. Nursed it home about 180 miles on I-95 that way.

That is why I asked the OP about fpdc numbers. With both pumps working he should be at 19-21% at idle. A bad pump will double those numbers.
My FPDC is 20 at 70mph, I think it's the same at idle, but I've never looked at it when idling.
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