HELP! Fuel Pressure Dropping.

[Blown99Snake]

My car's fuel pressure is dropping while at WOT above 5000 RPM's. I start out with 70psi of fuel pressure around 5000 RPM's, it drops to below 50psi by the time I hit 5900 RPM's, causing the car to start running lean. I have had the 03 Cobra fuel tank and pumps for about 6 months and it supported 512rwhp, but for some reason now, it drops on the dyno and the car doesnt even make but about 400rwhp around 5800 RPM's, so I know its not starving for fuel.

So...............................I changed the pumps out again tonight for brand new 03 Cobra pumps and also a new fuel filter and low and behold.............the pressure is still dropping.

Does anyone else know what the problem could be? Could it be in the MAF?

I am at a loss.

 

[white99gt]

What sized maf?

Why is the fuel pressure so high..Mine never got over 55 psi .With 42's and 555rwhp..
Sounds like the tune..HAve you made any changes to the car lately since it was tune for 512?

 

[Blown99Snake]

Only changed from an S-trim to a T- trim.

 

[PowerCobra98]

What size fuel injectors are you running? You never stated.

 

[white99gt]

Originally posted by Blown99Snake
Only changed from an S-trim to a T- trim.

ANd you didnt retune it?
What injectors and MAF?
Are you running a BAP?

 

[Blown99Snake]

Originally posted by white99gt
ANd you didnt retune it?
What injectors and MAF?
Are you running a BAP?

Yes, we attempted to retune, but fuel pressure dropped, so we couldnt finish.

42 Injectors and 90mm LMAF

No Bap.

Before I switched to the T-trim, this fuel system supported 512 rwhp. When I switched to the T-trim, I noticed the fuel pressure drop.

 

[white99gt]

The 90mm is probally pegging..AKA more air flow.Mine pegged around 500rwhp ..
And the cobra pumps should get bap to help them out..

 

[Blown99Snake]

But the car is only making 380/380 before the fuel pressure tapers off. The 90mmLMAF shouldnt PEG until after 500rwhp. I already made 512rwhp on this same setup. Only thing different was I had S Trim instead of T Trim

 

[white99gt]

Originally posted by Blown99Snake
But the car is only making 380/380 before the fuel pressure tapers off. The 90mmLMAF shouldnt PEG until after 500rwhp. I already made 512rwhp on this same setup. Only thing different was I had S Trim instead of T Trim

Then my only other guess is you are having the same issue i was..621 and my belt was slipping like crazy. Same pulley ,just swapped form a s to a T(different fuel setup but that did not effect the airflow).The 6 rib could not handle it..
Look at the blower area and see how much belt dust you have..I just finished doing my own 8 rib conversion..Its a night and day difference in the car..Now to get it back to the dyno..

Belt dust build up with less than 800 miles on the belt and blower:

 

[HISSMAN]

That is some crazy fuel pressure you are making in the beginning.

 

[Blown95Cobra]

my cobra is doin the same thing but i didnt change anything but injectors and maf. fuel stay at like 60 psi then drop to 35 or less after 5500 rpm.