I have a 1978 Delta 88 with the Olds 350 gas engine.

Normally it’s easy to start. One pedal pump, crank a few seconds, and it catches.

Lately it’s getting tougher. I let it sit for two weeks and went to start it. (In the past, two weeks or two months would have been no problem.). Pumped the gas pedal, cranked for 10 seconds, not even a cough. Gave it a rest, pumped the pedal several times, tried again, nothing.

I filled the carb bowl through the chimney and it started up fine. Took it for a drive and it ran well, idled nice, accelerated strong, no issues. Hot restart was instant.

Somewhere I read it could be the fuel pump siphoning the carb bowl dry? But - wouldn’t the check valve in the fuel filter prevent that? And if it was the fuel pump why would it run ok once started?

Thanks for some wisdom.

 

Fuel evaporates out of the carb over time. The pump refills this when you crank the engine. If the check valves in the pump get weak, wear, or otherwise don't seal properly, it can take a lot longer to get fuel back into the carb.

 

There is no possibility of the fuel pump siphoning the bowl dry. The air gap under the needle and seat prevents this.

It could still be a fuel pump problem as Joe said. Mechanical pumps can degrade over time such that they are not very good at pulling fuel from the tank at cranking speed. Combined with a dry fuel bowl in the carb from sitting a while would cause the problem you reference.

The pump could still be pumping well enough at idle speed and above to keep the carb full.

 

This is normal.

 

Also cracks in OEM hard rubber lines can make it hard as the pump is trying to suck fuel but instead just gets air.

 

^^^THIS^^^

If you haven't replaced the rubber fuel hose at the tank yet that's the first thing I'd do.