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.

 

[Cobra4pt6]

clogged injectors

 

[Blown99Snake]

Wouldnt the car run like total shit with clogged injectors? How do you clean or unclog injectors?

 

[lemosley01]

Why would clogged injectors cause the pressure to drop? I would think the FP would go up, not down (due to the restriction).

Is it possible that you're running out of electricity to feed the pumps?

 

[Quadcammer]

nah, i see 55 plus all the way to redline with 03 pumps and bap. 512rwhp shouldn't cause any such problems.

what is the a/f when pressure drops?

there are a number of things it could be.

1. fuel rail pressure sensor. cheapest, and easiest to replace. front of drivers side rail, 60 bux.

2. Fuel pump driver module. inner trunk panel, drivers side, a few connections and two bolts and its out. about 75 bux i think.

3. some sort of wiring or computer problem.

when did this start happening?

 

[Blown99Snake]

Ok, I think you put me on to something. When you say you see 55+ all the way to redline, what is the range? Does it hold at 55 or does it go up from 55?

I just realized it drops from 65 to 50 and then holds 50 all the way.

The A/F goes from 11.8 (3000-5200 rpm's) up to 12.8 (5800 RPM's, where we lifted) However, I made a few passes to see if the FP would drop farther and it didnt drop past 50 once it fell to 50.

 

[Quadcammer]

how much boost are you running?

12.8 is flat out too lean. no questions asked.

basically it will spike to 53 when i get into boost and hold at 55 all the way to 7500 and 15 psi. i have 55lb injectors so i don't need as much pressure.

what sort of injectors are you running and who did the tune? 50 psi of fuel pressure should be enough. i dunno why you aren't getting enough fuel.

 

[Blown99Snake]

Originally posted by quadcammer
how much boost are you running?

DOnt know yet, boost guage quit

Originally posted by quadcammer
what sort of injectors are you running?

42lb Bosch

Originally posted by quadcammer
who did the tune?

T&J Performance

 

[Quadcammer]

um, what is the blower/engine setup?

whats the duty cycle on the pump?

 

[Blown99Snake]

Stock block, Vortech T-Trim, 42's, AFM PP, 2003 Cobra tank/pumps, Paxton A/A/ IC, 90mm LMAF.

Not sure about duty cycle on the pumps.

 

[Quadcammer]

thats gonna be a lot of boost. probably at least 12 psi

maybe take it back to t/j

hard to diagnose without being there.

is it possible you are pegging the maf.

 

[Blown99Snake]

Originally posted by quadcammer
thats gonna be a lot of boost. probably at least 12 psi

maybe take it back to t/j

hard to diagnose without being there.

is it possible you are pegging the maf.

Dude.....the car already made 512rwhp on a 3.6" Pullied S-Trim. All I did was switch to a T-Trim w/ 3.6 and this happened. Im not new to the game.

 

[Quadcammer]

the t trim flows a shitload more air then an S trim.

the 90mm lmaf is probably pegged. 500rwhp + is usually the liimit for them

when you peg the maf you lose fuel control.

as for the power you are making, are you trying to pop the stock bottom end?