I have a 70 chevelle 454 with a factory Q-jet on top. I am having a problem with cold start up. After leaving the car sit all night, the car will not start. I used to be able to jump in, pump the gas pedal twice and the car would fire right up. Now, I have to prime the carb by pouring gas down the throat of the carb in order to get the car to start. This only happens when the car sits over night or longer. I took the air clearner off first thing, looked down thru the carb and moved the throttle(pumping the gas motion) and no gas squirtted from the carb. What should I be looking for? I thought about pulling it off to rebuild but I thought I would check and see what I could find here under the search function. I found all kinds off stuff for holley and such but nothing for a q-jet. What do you think? any links that could possibly help?
thank you for your time graemlins/thumbsup.gif

Those carbs often have a problem with leaking fuel well plugs.

Check also for a ruptured fuel pump diaphram.

If it's the wells, the plenum of the manifold will be soaked in gas. It will not evaporate that quickly because of the closed throttle blades.

No question here, the well plugs are leaking.
If it's ever been rebuilt with a rear well plug repair kit.......that will be where the problem is. These kits had a slide in pair of well plugs with an o-ring on them and a foam rubber diddy that went into the carb base to hold them in. Last a few years then leak worse than the stockers EVER did.
That said, take the base plate off the carb and look see. Probably have to disassemble most of the carb.
The rear well plugs are essentially in the center of the main body and hang down into the baseplate.

Also.....Q-jets more commonly leak from the front well plugs. These are between the primary bores and hang down through the baseplate. You can see them w/o taking the carb apart.

So here is what you can do.

JB Weld up both the primary and secondary well plugs. Use only JB weld. It works. Just coat them good and let dry for a day or so. The front ones are a tight fit in the baseplate, so you might have to file on them a bit to get the baseplate back on.

Have fun!

Ron

thank you gentleman graemlins/thumbsup.gif