I have ran my car(1992 Z28 TPI) for 2 years with the stock AC pump and regulator(44psi WOT). I changed to a Walbro 340. After I did that, my car ran like crap. I pulled some plugs(looked lean). I also changed the nozzle(shark NX) to the new 2 stage Shark Nozzle(NX).

I tapped into the feedline to the fuel solenoid(T). My new psi is 47psi(wot). The pressure stays 47 under WOT on motor. When I grab the bottle the pressure drops quickly below 20psi(let out quickly). My jets are for 44psi Fuel psi. I took out the pump and installed another one Walbro 340. The pressure is dropping. I checked the voltage It has about11.9-12.4 volts.

I never checked my old set up. Shouldn't the fuel psi remain at 44 or 47psi on or off the bottle(WOT). I pinched off the return line and the psi jumped to over 100psi. The fuel lines are stock. I replaced the fuel filter. I can't believe it ran fine with the AC pump and not with this one. I was wondering if my FPR is the problem?(it is stock).


What do you think?..please help.

 

I would definately check the pressure regulator. It's 11 years old,and TPI cars have had some problems with the stockers leaking.

 

I hooked a volt meter and watched my O2 reading while i was on the bottle. It stayed around .825-.850 The pressure still dropped from 48-50psi to under 20psi. the car was running good. I figured the O2 with that much pressure drop would be pretty lean. I desided to see if it was the regulator. I placed my Nozzle in a bottle,with the pump running I triggered the fuel soleniod. the pressure dropped to under 20 then I pinched off the return completely to take the regulator out of the picture. the pressure went up to about 25psi and stayed.

I thought the Walbro 340 was good to 500+ HP?. My motor is lucky to put around 300hp + 150HP N2O. I checked all the fuel lines for being pinched, checked the filter.

I thought the stock fuel lines would be good for what I wanted.

Anybody have any thought?