pump gone bad??car running lean

[308turbo]

been havin a problem with my car runnin lean and have not been able to figure it out ran fine on the tune for about 3000 miles all of a sudden just started runnin lean.....

my AFR is jumping around when cruising around on the highway and when idleing.....when i say jumping around its going from 14.5 to around 15.6 like a light which and jumping all in between there

i am almost positive i think that one of the fuel pumps are either going bad or is bad... .......
what are everyones thoughts on this?????if so wat pump or pumps should i put back in???

Anyone know what the stock fuel rail psi should be???


the car is pretty stock just 2.8 pulley exhaust intake sct tuner should be around 450 hp


thanks Robbie

 

[mike302]

I think I'm haveing the same problem? my car made 460/491 on dyno and after about 1 month after the tune my car dropped in power and went 13.00 A/F on full throttle

 

[JedWele]

Is it just running lean at light throttle or idle? If so it could just be your o2 sensor’s . Have you done any short burst of WOT to see what it looks like? There is also the possibility of you guage being wrong or wideband

 

[mike302]

my car was at 13.0 on the dyno

 

[308turbo]

driving around its fine its only when WOT throttle is when it leans out.. wideband is brand new...i have checked voltage wheile driving and everything the fuel pressure just is not going up enough when u hit the throttle


anyone ever have one pump go bad???

should i replace both with stock pumps??

 

[Fuxton]

just one of my pumps went bad. Its fine while driving normal but at full throttle it leans out real bad. Im replacing them both with GT pumps.

 

[308turbo]

yup thats wat mine is doing.....now im just trying to firgure out what to do with it.....should i get a stock pump again should i upgrade?? i dont plane on ever makin the car have more then 525 its only around 460 now and its going to stay that way for awhile...

anys tips???

thanks

 

[Fuxton]

i would think u would be fine with a stock pump. My tuner said that he thinks it the BAP causing my problem. Hes had quite a few cars do the same thing.

 

[308turbo]

i probly going to go with the focus pumps because that would be cheapest way for me since i not makin much power...

just trying to see if anyone else has heard of one pump going bad

thanks for quick responce

 

[jm@ReischePerf]

my AFR is jumping around when cruising around on the highway and when idleing.....when i say jumping around its going from 14.5 to around 15.6

It's pretty normal for your A/F to jump around at cruise/idle, those numbers look ok because the comp is constantly adjusting to stay as close to 14.7 as possible. What is your A/F at WOT?

my car was at 13.0 on the dyno

I think you have a fuel problem if your A/F was good before. Could be electrical: lack of available power (FPDC maxed out?) or BAP or pumps.

 

[Travizzle]

GT pumps w/ the mod. fpdm is an excellent way to go. Look up LethalPerformance, they have a nice package put together. Plus the added saftey knowing you don't have to worry about fuel problems.

 

[308turbo]

ya i just talked to my freind that told me that at cruise its normal.

but at wot it starts in the low 12s and moves right on up into the 13s if i ran it all the way out but i let off when it hits high 12s so i keep my head gaskets in place

 

[About2bite]

My Wideband reads a different afr from the dyno, it's just a little bit different but it's still not exact. Are these readings from your wideband?

 

[308turbo]

yes its from my wideband....the wideband in ur car is going to be more accruate then the one at the dyno usally because its closer in the exhaust pipe

 

[jm@ReischePerf]

but at wot it starts in the low 12s and moves right on up into the 13s if i ran it all the way out but i let off when it hits high 12s so i keep my head gaskets in place

What does your FPDC & fuel press look like once it starts going up?

 

[308turbo]

i had a computer for the fuel pressure i trying a matanical one tommorrow but when i floored it it was in high 12s and 36 psi which is obvisouly not right


whats fpdc stand for ??

 

[EvilTwins]

FPDC = Fuel Pump Duty Cycle

 

[mustangmike1]

I contacted Matt at the Mustang Shop in Calgary and he told me what to datalog when I had a bad hesitation above 4500rpm, I sent him the info and he told me that the fuel pump can't keep up, and the fpdc was maxing out by 4500rpm and after that the fuel pressure was dropping instantly or something along those lines. He told me to drop my tank and look for restrictions, broken or kinked lines, bad fuel pump. I dropped the tank and found out that someone had put a gt tank and an unknown single pump in my damn car before I bought it. I was impressed how he could tell what was wrong with my car by the datalog I sent him by email. My car was a 12,000 mile 1 owner from a 55 year old accountant(I wonder who swapped tanks). I still need a complete tank assembly if anyone has one.

 

[mike302]

try tousley if you want a new one!