My 68 XR7 GT has been sitting a while fixing the electrical issues and now it can start but with some work. It now hesitates and stalls out unless it has been warmed up for more than 10 minutes. I am using the original 600 cfm carburetor with proper automatic vacuum advance. The immediate thought was the accelerator pump which is now replaced. It now starts better but still hesitates. Could it be the check valve sticking or another minor adjustment? I use 91 or 92 octane non-ethanol gasoline which in the past ran fine in the rebuilt 390 GT.
Not very common but I have worked on cars with the pcv valve installed backwards or stuck open . A gigantic vacuum leak that can be overcome with carb adjustments but when you hit the gas or drop it in gear it just can’t keep up and dies
I would nspect the spark plugs. Fouled plugs can can act like that and it’s easy to eliminate as the problem.
I have to ask, how long is a while? Gas can turn in just a few months, longer if you use additive.
Gas tank was drained when car was not in operation and fresh non-ethanol gasoline was placed in tank (5 gallons to start) Gas tank was replaced in 2020 so I don’t think that a bad gas tank is the issue.
The fuel filter at the carb was replaced after the initial start as it seemed to be picking up trash from the lines or tank.
I discovered that the if there is any debris in the tank, pump, and lines, it will end up plugging the carb. You would think the fuel filter would prevent that, but the very fine stuff gets right through.
We added a larger fuel filter under the power steering pump before the fuel pump to help filter out debris. The filter at the carb is very small. If the trash was left over from the fuel lines I think it would clear out in 10-15 minutes.
I can check the fuel again to see if any debris is still coming through from the lines. I know a tank can’t be drained completely even with the drain plug but it seems like the debris would be gone by now.
Mine seemed to take forever to clear the debris out. Of course I did not change out the fuel lines or pump like I probably should have. But I could see the fine tan powder-like sediment accumulating in the bottom of my carb bowl. OEM style fuel filter at the carb didn’t catch it. Ran like crap until this all got out of the system.
The air bleeds in the carb tend to gum up when the car sits. I would try some carb cleaner down the bleeds.
On top of what Bill says - gas goes bad and when it does it is useless for anything other than weed killer. I would drain the lines, drain the tank and inspect all the fuel components thoroughly. Likely they are fine but the possibility exists that they aren’t. The fuel pump, fuel lines, and tank may need to be replaced if they are bad enough.
Cars hate sitting idle. They need to run regularly.
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Pri-G will preserve unleaded gasoline for a year.. if I’m store anything for an extended period that runs on gasoline I fill the tank with 100 octane low lead so long as it’s an old school engine without O2 sensors or a catalytic converter.
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