I have a ’78 silver anniversary, small block, that I can’t get started.

Prior to this issue, I had rod problems, and my mechanic made the necessary repairs. Worked fine. Sometime later, I started having problems starting the car, which required me to have it towed in. He replaced the carburetor with a rebuilt one, and the day I picked it up, it fired right up. Started right up the next days as well.

However, if I don’t start the car after a few days, IT WILL NOT START. It will turn over but not fire. After a minute or two of cranking, it will begin to sputter, and with a bit of gas pedal coaxing, it will run. When I disengage the gas and press the brake to shift (Automatic), it dies (won’t hold an idle until warmed up) but then runs perfectly. The next day, it will start exactly as it should. If I let it sit for a few more days, the same problem occurs, requiring me to take it back to the mechanic to adjust.

This is a reoccurring issue—three times now. He’s adjusted the carb each time but to no avail. Neither he nor I know what is causing this issue. My unmechanical guess is that after sitting a couple of days, it is “collecting” moisture, causing it to just turn over and not fire.

Full disclosure: This is an inherited vehicle that sat for 14 years or so. I am not as mechanically involved with it as I should be, but that being said, I love my Vette and have gone to great expense to get it running. My mechanic is very competent. He services my other two vehicles and has owned a couple of Corvettes himself. Five other C3 & C4 owners (whom I know of) take their work to his shop.

Thanks for your recommendations.

Steve Holtz
Sautee, GA

 

All start/run issues need to check basics. Fuel, air, spark, compression. Your mechanic or you need to know how to check all these. It would be too lengthy to try and post all of this in a response. I'd go back to the rod issue and do a compression test first thing and make sure it's healthy then check spark, carb and timing.

 

Do you smell fuel after it has sat awhile?
Mech replaced the carb? What kind?

I suspect your fuel bowls are empty after sitting a few days.
Some Quadra Js has issues with leaks in the bottom of the bowls. Look for damp areas under the carb and sometimes manifold paint will be missing or peeling.

Just working the throttle looking in the venturi for a fuel squirt is not enough of a bowl capacity test.
Accelerator pump "wells" often have fuel, even the though the bowls are empty.

And moisture is not a concern of a "No Start" issue.
In fact, back in the day, GM introduced water into the fuel system to save gas.

 

I’d agree with others, it sounds like fuel is draining back down from your float bowl. If you don’t have a windowless seat I would consider getting one. Adding a couple ounces of gasoline through the vent tube on top before you try starting it after a couple days would let you know if that’s your issue.

Even then, that sounds like a long time for the engine to turn over before getting gas up to the carb from the fuel pump, what is your timing set to?

 

I have the same issue with my '68 big block when it sits for a few days and wondered if the gas was vaporizing, since I don't see fuel on the manifold anywhere. If I fill the vent bowls with 2 or 3 oz of fuel, it fires right up. It's a Quadrajet that was professionally done and it runs great. Choke and pull off are set right, it just seems to lose fuel when it sits. I don't know if it's related to your problem or not.

 

Thank you all for your feedback and suggestions. Meeting with him this AM.

 

I have a 77. When I had a carburetor, I actually had 2 different ones. I would always need to crank it twice to get it to start as the fuel would need to brought back forward if the car sat for more than a few days.
I converted to fuel injection about 5 years ago. In tank fuel pump. No issues whatsoever anymore. Fires straight up regardless how long it sits. Back out of the garage instantly.
You couldn't pay me to have a Automatic transmission however.