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. Apparently, 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 local owners (whom I know of) take their work to his shop. 

Thanks for your recommendations.

Steve Holtz

Sautee, GA

Typical welch plugs leaking on the bottom of the carb fuel bowl. Your mechanic apparently did nothing to them on the rebuild. When they leak, usually after a couple of days, the fuel bowl is empty, causing you to have to crank on the engine until the fuel pump refills the fuel bowl, then it will start. They can be epoxied, or replaced, to stop the leakage. Epoxy is the quickest, but you have to make sure there is not too much epoxy to keep the base plate from bolting back up to the bowl.

Joel Adams
C3VR Lifetime Member #56    
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

100% agree with Joel's diagnosis.  

My recommendation: buy Cliff Ruggles' book on Q-jets. Share it with the mechanic.  There is the common epoxy method Joel mentions, but there is also a way to remove the plugs, thread the bores, and then put screw plugs in.   There's a wealth of information in there besides the plugs.  The problem of it not holding an idle when cold actually sounds like a choke/fast idle adjustment problem to me.  

There's also Doug Roe's Rochester Carb book.  It's good too, and has a few things that Ruggles' book doesn't have, but it's more general - covers other carbs than just q-jets.  

 

Thank you for your feedback.  Meeting with him this am and will share.

"Lars" on Corvette forum is the quadrajet guru over there.  Here is his profile page on the forum.

I can get his email if you want.

https://www.corvetteforum.com/forums/members/2251-lars.html 

He probably knows more about quadrajets than anyone else and will even overhaul them.