So converted my car from tbi to carb 355 with a cam, quick fuel 650 ss, carb, have Mallory return fuel regulator. ran awesome for 2 years. Been chasing gremlins all summer!
So here is the problem now had it ready to take out for first time all summer running good, put some fuel in to get to gas station and all of a sudden started running like crap rpms wont stay up fuel pressure dropped from 7-8 psi to 3-4 psi. put car in drive stumbles and dies. If I just tap the throttle linkage on car it runs fine for a minute then the same thing happens. Just stumped changed fuel filter earlier this summer so brand new. Any ideas would be greatly appreciated.

 

Sounds like you may have bad fuel pump. Are you using the in tank pump with the mallory reg or have you replaced the pump with something else?

 

Was it running just fine BEFORE you put fresh gas in it?

could be the fuel pump but I'd track down the fuel itself, call that station and ask if they had any complaints recently. You could have gotten bad fuel.

 

Thanks for replies, yes using the in tank fuel pump it came with, with Mallory fuel reg, fuel pump looks like has been replaced by previous owner that cut access panel in trunk with what looks like a swiss army knife can opener (total hack job dirty socks stuck in it to cover sharp edges).
I was leaning toward pump, but doesn't make sense that when you hit gas it doesn't act like it is starving for fuel it runs good.
I also don't thing it is the fuel because I used the same pump and fuel for my truck and it is fine.
I wondering if it has to do with the carb being stuck (open for lack of a better term).
Gonna check fuel pump pressure out of tank tonight we will see.

 

Idk why I didn't say this at first but have you checked for vapor lock? (i.e. the fuel vaporizing before it gets into the engine?)

That was an issue I had with my carb'd engine.

 

Again thanks for the ideas. Let the car sit for a day or two. Now it runs fine and I let it run for an hour.
The only observation that I made in that hour cause I watched the fuel pressure gauge like a hawk, is that the fuel pressure slowly dropped. So I turned it up on the regulator and I was running at 15psi which is what the pump should run at for a tbi pump if I am not mistaken. Now for my theory, and let me know if you think it is far fetched, is that when it is running there is crap in the tank and it slowly gets caught in the tank prefilter on the pump which slowly drops the fuel pressure. The fact that I added gas to the car sturd that crap up and it clogged the prefilter. The only thing that doesn't make sense is that the pressure could still get up to 15 psi on the pressure gauge.

 

Ok so did a ton of online research and found a lot of people with same problem with the gauge showing wrong pressure when car is running turns out that if you have a liquid filled fuel psi gauge under the hood it heats the liquid up and shows a lower reading than what is actually going through the line. Gonna try setting the psi when cold then add some gas tomorrow and see if it does the same thing. I am thinking that I may have upped the pressure so that it is way off, but I can't remember.