Cliff's Quadrajet Parts and Rebuild Kits

Quadrajet Problem Solving => Diagnose a Quadrajet carburetor problem => Topic started by: JonGM13 on November 03, 2022, 08:20:50 AM

Title: not starting when hot unless pouring in thimble of fuel in top!
Post by: JonGM13 on November 03, 2022, 08:20:50 AM

Hi from the UK,  I have put my Quad back on a rebuilt engine. All standard.  I have cleaned and redone the butterfly bushes.  Other than that it is all set as std.  When she is hot she stumbles and if stalls she will not restart unless I have poured a small amount (thimble size) of fuel straight down the carb. Then she starts.  I am struggling now to think about what is next. I have clamped off vacuum pipes and still no joy.  When she is cold then fine she's OK.

Title: Re: not starting when hot unless pouring in thimble of fuel in top!
Post by: Cliff Ruggles on November 04, 2022, 06:11:26 AM

Carburetor part number?

Application?

What exactly has been done to it?

Do you have pump shot from the accl pump?  Doesn't sound like it if you have to remove the air cleaner and pour gas into the carb.

The stumble/stalling part would NOT be related to bushing the throttle shaft.  Could me many other things, like a vacuum leak someplace, flooding, etc.....

Title: Re: not starting when hot unless pouring in thimble of fuel in top!
Post by: JonGM13 on November 26, 2022, 09:29:27 AM

Found that there was a leak in the intake manifold between the head and intake.

That problem is now sorted starts, runs, idles.  But we are left with one annoying problem. with the engine running at 800-900rpm select drive on the 700R4 box the engine dies. BUT if the last step on the fast idle is still on select a gear and stays running.

Title: Re: Now running but another problem has raised its ugly head!
Post by: JonGM13 on November 26, 2022, 09:32:48 AM

The Carb number is 17066553   0898.
Have tried different springs but still does it.

Title: Re: not starting when hot unless pouring in thimble of fuel in top!
Post by: Cliff Ruggles on November 27, 2022, 05:29:24 AM

What springs?  Power piston or distributor?

Title: Re: not starting when hot unless pouring in thimble of fuel in top!
Post by: Kenth on November 27, 2022, 07:18:35 AM

Are you adjusting the idle mixture screws in gear for best idle/vacuum at 650 rpm´s?
How many turns out from bottomed are the idle mixt. screws?
How much intake vacuum at best idle in gear?

Here are some considerations for your 1980 Chevy 305 carb.

With .069" upper idle air bleeds, .077" lower idle airbleeds and .109" idle air bypass the .032" idle tubes needs to be opened some with todays ethanol-blended fuels. Start with .035".

Also, the main jetting #71 jets and 49P rods is way too lean with the upper and lower .120" main airbleeds. I would use at least #76 jets.