Fuel system help

[johnplogii]

I believe we have a fuel problem on a friends car. The car has an atr double pumper, new filter, 72lb injectors. With only the main pump connected the car runs pretty well but as boost goes up fuel pressure goes up then drops to about 35psi under wide open throttle 21psi boost. The thing is it still pulls strong & doesn't miss or hesitate. With the second pump hooked up the fuel pressure ramps up with boost to approx 60psi but the car spits & sputters like it should have done when the pressure dropped to 35psi. Any ideas? The one pump should be enough unless the pump is weak. Any help is appreciated.

Thanks

John Plog

 

[johnplogii]

Anyone?

 

[Chuck Leeper]

My $.02

You sure the gauges are correct? I think that you would have other issues if the system PSI was only 35#, and the engine was running at 21psi...35psi should/could have made the engine detonate, but probably not sputter/miss. The 35psi could be the result of the inj flow out running the single pump. That may indicate the pump is on it's way out.
Could be the return line is kinked, bent, partially plugged, and when the 2nd pump comes in, the engine is flooded??
Any WB readings?
Have you gone thru the ign system?
Plug readings?
I'd start at the back and work forward.
Drop the tank, check the pumps, lines, voltage, etc.
FPR is? Accufab, etc? Working properly?

Is this a fresh build, or something that has been purchased, and you are trying to tune it?

 

[johnplogii]

You sure the gauges are correct? I think that you would have other issues if the system PSI was only 35#, and the engine was running at 21psi...35psi should/could have made the engine detonate, but probably not sputter/miss. The 35psi could be the result of the inj flow out running the single pump. That may indicate the pump is on it's way out.
Could be the return line is kinked, bent, partially plugged, and when the 2nd pump comes in, the engine is flooded??
Any WB readings?
Have you gone thru the ign system?
Plug readings?
I'd start at the back and work forward.
Drop the tank, check the pumps, lines, voltage, etc.
FPR is? Accufab, etc? Working properly?

Is this a fresh build, or something that has been purchased, and you are trying to tune it?

The guage is a new one from postons, just installed last week. My friend has had this car with this setup for 7-8 years. It ran 11.20's a few years back then developed problems. Checked all the fuel lines we could, didn't find any kinks. No wideband readings but I did get a reading of .840-.820 running on the one pump at 21psi boost/35psi fuel. New plugs/wires no readings. Fuel pressure reg is good it came from my car recently. I am going to go get the car today & bring to my house to further investigate.

Thanks Chuck

John Plog