I'll list what is new (less than 600 miles). Okay, EVERYTHING is new. The only thing original on my car is the unibody. I'm talking fuel filter, in-tank pump (on my 2nd one), injectors, fuel rails, regulator was re-used but isn't leaking gas into the vacuum reference line to the plenum. Plenum, TB, , fuel filter, ENTIRE engine new. Exhaust, headers, gaskets...new.

The car ran great from April to Late July. I did have to cut an area on my heat shield that runs over the axle tube because my 4" mufflex pipe hits. Now there is a tangenial area the size of a penny on the over the axle exhaust pipe touching my gas tank. That was one thing that had me concerened.

The symptoms are my fuel pressure leaks down after key on from 44psi to about nothing in less than five minutes. Also when I step on it (light acceleration, heave, hammering on it) my fuel pressure drops to 30psi, but when I let off the throttle it snaps right back to 44psi.

The vacuum at idle is around 11" and in cruise upwards of 20". Specs of car are below:

 

Does it hesitate under this condition? Does your wideband show lean when the fp drops?

 

She hesitates, almost feels like its missing when the FP drops. Datalogs show the AFR is good though when that all happens.

 

ttt

 

what kind of pump?

 

Intank is the GM replacement Walbro 255lph.

 

Who's pump?

Did you upgrade the wiring?

Stock fuel lines?

 

Walbro 255lph pump from AEPerformance in TX. The lines are stock from the pickup up to the front rail. I run -8 to the pass side rail and -6 to the regulator. Only wiring upgraded was the connector the pump came with. Again, the car ran FINE since April until now.

 

Get a kit from racetronix with the pump and wiring. The stock wiring sucks. It may have been OK when you put the new pump in at first, but I'm guessing the voltage drop has killed your new pump.

I also think you need to run bigger fuel lines with your engine. Stock lines restrict the flow and between that and the stock crappy wiring it puts a lot of stress on the pump, hence your problem.