I'm at wits end with this damn cobra!!

[racin4ds]

Ok guys, need some serious help here, I've owned my Cobra for a little over two months now, shortly after I bought the car it developed an issue of not pulling past 5000rpm, it goes flat and bucks violently almost like someone is pulling a plug! Other than that it runs perfect down low and around town. This problem only exists when I go WOT. The car builds boost and holds it steady throughout so its not belt slip.

A little history on the car:
48k miles
only mods are JLT RAI, 2.76 upper and 3" catback
Diablo Predator tuned. (yes it does this on the stock tune also)

Plugs are Brand new TR6's gapped at .032
MAF is clean
No MIL

I've done some datalogging with the Diablo and see nothing out of the ordinary, fuel pump DC only goes to 50% before it starts breaking up, no misfires detected, what else should I look for?

:shrug::shrug::shrug:

 

[DarkMach1]

Fuel filter?

 

[racin4ds]

Funny you mention that, just picked one up and installing this evening so we'll see! God I hope its something that simple!

 

[racin4ds]

If it was a coil I would surely see it as a misfire code and an MIL right?

 

[racebronco2]

A little history on the car:
48k miles
only mods are JLT RAI, 2.76 upper and 3" catback
Diablo Predator tuned. (yes it does this on the stock tune also)

Plugs are Brand new TR6's gapped at .032
MAF is clean
No MIL

I've done some datalogging with the Diablo and see nothing out of the ordinary, fuel pump DC only goes to 50% before it starts breaking up, no misfires detected, what else should I look for?

:shrug::shrug::shrug:

That's your problem ... when datalogging with the predator, 50% x 2 =100%.
You maxing out your pumps. Sct the values are correct but the predator you must times it by 2. The fuel pressure should be dropping at the same time you pumps are maxing out.

 

[racin4ds]

That's your problem ... when datalogging with the predator, 50% x 2 =100%.
You maxing out your pumps. Sct the values are correct but the predator you must times it by 2. The fuel pressure should be dropping at the same time you pumps are maxing out.

Are you serious and 100% sure of that? I had no idea! How could I be maxing my pumps with an almost stock car using only an upper pulley? :??:

 

[racin4ds]

Thanks racebronco2, I just confirmed with Diablo (not that I didn't trust ya just that I'm a facts person

So I must have a bad pump?, my car is nowhere near capable of maxing out the stock pumps yet with my mods.

 

[03cobra#694]

Not uncommon at all. One of my logs, 2.76'' upper only. My maf and pumps are right there...

 

[racin4ds]

Damn.... I guess its a good thing, means I'm making some decent power I suppose!

 

[spitin venom]

I maxed my pumps with a 2.93 upper only. Once I installed the BAP my fpdc dropped down to 76% at redline. Don't forget to change the fuel filter often

 

[racin4ds]

I'm actually thinking I have a bad pump, my DC% is reading 36-40%(72-80% actual) at regular cruise!

 

[2003cobraguy]

im running 97% fuel pump duty cycle on only a 2.8 upper, intake, and exhaust cobra.

yes i made 480 rwhp, but u can max out easily.

 

[racin4ds]

After some datalogging today I'm convinced I have a bad fuel pump, I'm cruising at 58-60% FPDC and its at 100% DC before I even get to 4000rpm. Of course all along my damn diablo has been reading only half so I was ignoring the FPDC thinking it was fine!

What kinda FPDC% are you guys seeing at idle and 60mph cruise with GOOD systems?

With just an upper pulley and catback I should be OK with stock 03 pumps shouldn't I? Cant really afford to do the GT pumps and upgraded FPDM at the moment...

 

[Ironhand]

It may be a bad pump or it could be a PPRV delete with a line pop off. A sock on one of the pumps can also gotten messed up or clogged. So time to drop the tank to atleast see if anything is wrong. And if your gonna replace a pump, might as well put twin FGT pumps in it and go from there.

 

[spitin venom]

After some datalogging today I'm convinced I have a bad fuel pump, I'm cruising at 58-60% FPDC and its at 100% DC before I even get to 4000rpm. Of course all along my damn diablo has been reading only half so I was ignoring the FPDC thinking it was fine!

What kinda FPDC% are you guys seeing at idle and 60mph cruise with GOOD systems?

With just an upper pulley and catback I should be OK with stock 03 pumps shouldn't I? Cant really afford to do the GT pumps and upgraded FPDM at the moment...

At idle I am around 35% FPDC.

 

[racin4ds]

Never thought about the PPRV hose coming off, I'm really not sure if the PPRV is still there or not, as I said I've only owned the car a couple months and not 100% sure of the previous owners mods to it...

 

[Bruha]

that's your problem ... When datalogging with the predator, 50% x 2 =100%.
You maxing out your pumps. Sct the values are correct but the predator you must times it by 2. The fuel pressure should be dropping at the same time you pumps are maxing out.

+1

 

[boxinabag]

you and I are in the EXACT SAME FREAKING BOAT!

I just got my new pumps, but than my level sensor broke, had to order a new one, waiting for it to get here tomorrow. And to top it all off, my fuel filter ends dont have the retainer in them to hold my fuel filter... I am about to drag this car to mexico and report it stolen... it is starting to really make me mad :cuss:

 

[racin4ds]

Well, changed the fuel filter last night since It appeard to be an OEM motorcraft piece and was hoping for the best but..... nope. Started her up and still had FPDC of ~60% at idle. Can anyone confirm this when they had a bad pump? Could it be my FPDM??

 

[boxinabag]

Well, changed the fuel filter last night since It appeard to be an OEM motorcraft piece and was hoping for the best but..... nope. Started her up and still had FPDC of ~60% at idle. Can anyone confirm this when they had a bad pump? Could it be my FPDM??

That is exactly what my car was doing. You probably have a bad fuel pump.

I ended up putting my new fuel filter in, even though the garter spring is missing (if I have to I will just cut the lines and use rubber fuel lines and hose clamps to seal it). Today i should get my new Fuel Level Sending unit in and will get it all put back together. Once that is done I will test to make sure I don't have any leaks and take it for a quick drive.

How bad was your fuel filter? Did you try blowing through it? Mine was pretty bad, and could have been the cause of one of my pumps going out.

I will let you know how mine ends up tonight after the new fuel pumps. I hope it fixes my problem. If it does, I am going to say that you need to get some new fuel pumps.