Car going lean at WOT.

[Z O SICK]

What's up fellas? My buddy's 03 Cobra is going lean at wide open throttle. The tune is fine. While making a pass on the dyno the car went lean. While cruising the A/F is 14.7. As soon as he goes wot, it goes really lean. I'm thinking it's the FRPS or the fuel pump is starting to go. What do you guys think? Thanks for your help.

p.s. He has a whipple and this happen with the 23lb pulley on while on the dyno.

Thanks,
Tony

 

[sambandit]

Well, at the risk of soundin weird, how do you know the tune is fine if the car is going lean?

Also, are you sure the fuel system is up to snuff?

 

[Z O SICK]

Well, at the risk of soundin weird, how do you know the tune is fine if the car is going lean?

Also, are you sure the fuel system is up to snuff?

I'm just going off what my buddy was telling me. To be honest, I htink he may be pushing it with 23lbs. He went back to 17 lbs and it's still doing the same thing.

 

[eaglesnick]

Check the alternator output, there is a thread on this forum about it. Alternator may not be putting out enough voltage for the fuel pumps at high rpms.

 

[Juruense]

Maybe he needs a BAP?

 

[03yellow]

Sounds like hes running out of fuel:

what are his mods?

 

[jophis37]

Thanks for the input guys, It's my car that was having the issues. I ran one run w/ the 2.75/4lb combo on and it was fine all the way up to 6000rpms, after that the A/F spiked up9 lean) every run we did after that we had to shut it down right away. The A/F wasn't dropping. It actualy went up. Well I checked the BAP fuse and it was fine. I decided to call it a day and limp home. The car drove fine. I live 190 miles from the dyno and as long as you didn't go WOT the car acted like nothing changed. I pulled over at a gas station half way back where a friend was going to meet me to help troulble shoot the issue. While I was waiting I decide to check all fuses, grounds, power wires and connectins in general. Nothing. I unpluges the FRPS so I could switch it out w/ my friends Cobra, but they still hadn't showed up yet. So while I was waiting in the car, I decided to see how it would idle if the frps was out/disconnected. It seemed to idle alright. It did thorw a code though. So I shut it down cleared the code. After I hooked the FRPS back up, started it up again, no code. Well Since my friend still wasn't there, I decided to take a drive to see if I could notice anything else that would help us trouble shoot. And guess what? The fist time I got on it, the fuel dipped right down. I took it on the highway to get a nice run on it, and it was fine. As if nothing had ever happened. Has anyone ever heard of the FRPS meesing up like this? The last time mine went out was on my previous 04 cobra, and when it went out, it was done. the car could not drive.

 

[03yellow]

Do you have stock injectors and fuel pumps?

Maf extender?

 

[jophis37]

Stock fuel pumps, but 60 lb injectors. I know I'm not even close to maxing out the injectors, but I'm probably right at the edge of maxing the fuel pump. I also have the SCT 2800 maf, I'm not pegging that either. What gets me is that it's back to normal. I know the FRPS's are known to go out, but if it was the FRPS, would it had just started working like mine did after a while?

 

[03yellow]

I thought 550rwhp was max on the stock pumps.

The frps can have a slight tear or the diaphram can pull loose. You might want to replace it anyway...I had one that was acting up and didnt go out right away. Do you have the KB disk in the frps?

Stock fuel pumps, but 60 lb injectors. I know I'm not even close to maxing out the injectors, but I'm probably right at the edge of maxing the fuel pump. I also have the SCT 2800 maf, I'm not pegging that either. What gets me is that it's back to normal. I know the FRPS's are known to go out, but if it was the FRPS, would it had just started working like mine did after a while?

 

[Venomous01]

I'm just going off what my buddy was telling me. To be honest, I htink he may be pushing it with 23lbs. He went back to 17 lbs and it's still doing the same thing.

These engines can take up to 28lbs of boost before the head gaskets start to go. I have even heard of some reputable shops stating up to 30lbs before they go...

 

[Venomous01]

Thanks for the input guys, It's my car that was having the issues. I ran one run w/ the 2.75/4lb combo on and it was fine all the way up to 6000rpms, after that the A/F spiked up9 lean) every run we did after that we had to shut it down right away. The A/F wasn't dropping. It actualy went up. Well I checked the BAP fuse and it was fine. I decided to call it a day and limp home. The car drove fine. I live 190 miles from the dyno and as long as you didn't go WOT the car acted like nothing changed. I pulled over at a gas station half way back where a friend was going to meet me to help troulble shoot the issue. While I was waiting I decide to check all fuses, grounds, power wires and connectins in general. Nothing. I unpluges the FRPS so I could switch it out w/ my friends Cobra, but they still hadn't showed up yet. So while I was waiting in the car, I decided to see how it would idle if the frps was out/disconnected. It seemed to idle alright. It did thorw a code though. So I shut it down cleared the code. After I hooked the FRPS back up, started it up again, no code. Well Since my friend still wasn't there, I decided to take a drive to see if I could notice anything else that would help us trouble shoot. And guess what? The fist time I got on it, the fuel dipped right down. I took it on the highway to get a nice run on it, and it was fine. As if nothing had ever happened. Has anyone ever heard of the FRPS meesing up like this? The last time mine went out was on my previous 04 cobra, and when it went out, it was done. the car could not drive.

Did you have Greg tune the car? Are you running a BAP? It sounds like you're not which if you plan on running 23lbs of boost you DEFINITELY need one. Also sounds like your pumps are not getting the kick they need to supply adequate fuel at the higher RPMs.

 

[jophis37]

Did you have Greg tune the car? Are you running a BAP? It sounds like you're not which if you plan on running 23lbs of boost you DEFINITELY need one. Also sounds like your pumps are not getting the kick they need to supply adequate fuel at the higher RPMs.

I ran Greg's tune minus 2*, I do have a BAP. The rest of my fuel system should be good, I'm probably close to maxing my fuel pump ot on the 23 lb setup though.


Does anyone know where I can get a FRPS from other than FORD. Or is it Ford specific?

Also I'll be looking into getting the KB FRPS disk.

 

[jophis37]

I just called my local Ford for the FRPS, they told me $101.00, not including TAX, and they won't give me a part number over the phone. They're worried that I might go through another dealer for the part. For that price I can see why they might think that.

 

[ShelbyGuy]

its a stock item at licoln-mercury dealers

thank the guys at your ford dealer for the stick-it-up-the-pooper price. thats no way to gain repeat customers.

 

[jophis37]

Well I called another Ford store and got qoated $130. Man these things have gone up. I payed $55 a year and a half ago. I guess w/ all of us modding our cars and blowing the FRPS's we've really caused these things to go up. Can't blame Ford for trying to make money. But you can hate them for it. Anyone know ehere to get the best price?

 

[jophis37]

I just found out about Steve, who offers 10% plus cost. This site just saved me $50+.