When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
1978 L48 bone stock except recurved distributor per Lars timing papers. Usual hard starting when sitting for several days. (Need to put in a windowless needle seat I suspect).I drive to my volunteer job and it sits for about 5 hours before returning home.
In wintertime in Colorado it will crank right up with maybe half to no accelerator pedal.
Lately in warmer Springtime temps it grinds and will not catch. Pulling the air cleaner reveals very gassy rich fumes. So I let it sit and hope it clears. Try again holding pedal wide open. Grind grind grind. No start . A quick shot of ether brings it to life on first revolution.
I rebuilt the Qjet ( a year appropriate service replacement) about 4 years ago and it has been great until this Spring. Strong squirts from accel pump jets.
1978 L48 bone stock except recurved distributor per Lars timing papers. Usual hard starting when sitting for several days. (Need to put in a windowless needle seat I suspect).I drive to my volunteer job and it sits for about 5 hours before returning home.
In wintertime in Colorado it will crank right up with maybe half to no accelerator pedal.
Lately in warmer Springtime temps it grinds and will not catch. Pulling the air cleaner reveals very gassy rich fumes. So I let it sit and hope it clears. Try again holding pedal wide open. Grind grind grind. No start . A quick shot of ether brings it to life on first revolution.
I rebuilt the Qjet ( a year appropriate service replacement) about 4 years ago and it has been great until this Spring. Strong squirts from accel pump jets.
Not sure where to start looking. Float level?
Unless you fully depress the gas pedal at least once on a totally cold engine the choke and fast idle function will not completely engage.
Have you checked the choke adjustment on a cold engine?
At air temperature of 72 the choke should barely close completely.
What did you set the float level to when you rebuilt the carburetor?
The hard starting after a few days could be just a dry floatbowl.....I've read that when the engine has just been shutdown it heats the fuel up to the point where it gasses off and evaporates 1/2 the bowl capacity in just a couple of hours. The rest just evaporates.
In wintertime in Colorado it will crank right up with maybe half to no accelerator pedal. That's because the choke is doing it's job
A quick shot of ether brings it to life on first revolution. This to me says it needs a few pumps of the gas pedal prior to starting to get some fuel in the intake.
Melwilf-i set the float to 15/32” and the choke of to 2 lean. Pics show the choke before and after on a cold engine at 70*F Choke after pedal depress Choke before pedal depress
The way to actually see how much the choke is opening when the car is on high idle will require removing the air cleaner and pushing the choke pulloff all the way in.
Last edited by Piersonpie; May 15, 2026 at 07:52 PM.
Melwilf-i set the float to 15/32” and the choke of to 2 lean. Pics show the choke before and after on a cold engine at 70*F Choke after pedal depress Choke before pedal depress
I think you need Lars paper on tuning a Quadrajet, float level sounds high and if you have a window seat that contributes to the problem.
2025 c3 ('68-'73) of the Year Finalist - Unmodified
2025 C4 of the Year Finalist - Unmodified
2025 C8 Stingray of the Year Finalist - Unmodified
After a few days I believe the gas has evaporated from the carb. I prime my carbs thru the air horn in a situation like this.
Im guessing the 5 hour situation may be from gas boiling/evaporating in your carb. The area gas companies probably haven't switched from winter formula yet and the increased temps are causing your problem. I had a vehicle that ran great in the winter, had problems in the spring, then ran great again in the summer.
Make sure the choke partially opens when cranking it. My car used to flood out when it was cold because the choke pull off vacuum diaphragm wasn’t opening the choke plate when cranking it. I think it is supposed to open 1/4 inch when when you are starting it when cold.
Put a vacuum tester on the diaphragm to see if it holds vacuum. If it bleeds down then you have found your problem. While you're in there with the vacuum tester.....put it on the HEI diaphragm as well.
KENS80V- I pulled the choke vacuum break and tested it. Will hold vacuum and has the required slow rate relaxation rate when vac is disconnected. I read one of Lars’ rebuild threads and will set float to 0,300” when I open it up once I get some parts from Cliff Ruggles.(float/needle /seat Thanks everyone for the help and suggestions. I will report back after the new parts go in.
Flood after sitting 5 hours
