1967BuickGS400

Hello everyone. I just swapped a 2001 LS1 into my 67 buick gs. Im using the Holley HP EFI to run it. I finally was able to fire it up last Friday and it was idling up and down then it would stall. I figured it might be fuel related so I ordered a pressure gauge. I just got the test gauge and hooked it up to the fuel rail. The pressure was fluctuating from 64 to 40 at idle. If I revved it when it got to 64 the pressure would drop to 30 and it would almost stall. I am running a vette fuel pressure regulator. The FPR is mounted about 7 feet from the in tank pump. The pump is a Walbro GPA series in tank pump. 6 AN lines for supply and return. Im thinking theres something wrong with the FPR but im not sure. What do you guys think or what info do you guys still need? I did pick up an adjustable Paxton EFI FPR but if the regulator isn't the problem then I don't want to put it on.

1967BuickGS400

I changed the FPR and set it for 58psi. I did notice the fuel pump cycling on and off and I don't think it should be turning off. That is were im getting the fuel pressure drop. Some times it doesn't turn back on until 20 psi. My brother said since its a return style fuel system the pump should run 100 percent of the time cause any unused gas goes down the return line back to the tank and I agree with him. Is there a pressure sensor on a walbro pump that is making it turn off? If so can it be turned up or bypassed?

Old Geezer

iTrader: (3)

Quik answer = No.
Hot wire the pump, and see what the psi does. If it's steady, the issue is in the wiring.

1967BuickGS400

Thanks for the advice. Got it working now. I hot wired it like you suggested and it worked great held right at 58 psi. I worked backwards from there and it ended up being the fuse able link going to my fuel pump relay kept tripping.