Won't idle without choke

Matt Colie

Matt Colie

Well-known member
Aug 15, 2008
11,101
807
113
South East Michigan near DTW
> 77 403, starts fine on choke, the dies as soon as choke drops off.
> It's been sitting a while, gas old mixed with new, new fuel pump with electric pump kicker, inline fuel filter, new carb filter, lost spring, got
> one at hdwr store, not sure if it's the right one..
> Any clues on where to start?
>
> Thanks,
>
> Jim

Jim,

The idle circuit is very possibly fouled because of the old fuel. If you pour some fuel system cleaner in there, it might clear out. But until it
does, try adjusting the idle stop to get by. This will only be temporary and be real ready to take out what you put in. So, count how much you do.
I always count quarter turns because it is easy.

The idle mixture screws are under the float bowl and a bear to get to without the proper tool. Just leave them alone as long as you can.

Matt
--
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
 
Years ago...MANY years ago...my dad had a Oldsmobile that had a V8 with a QJet. Also had the same issue of not idling. Using compressed air, I pulled
the idle screws out and blew some compressed air through them. Put the screws back in all of the way and backed them out 1 1/4 turns. Started the
motor, waited for warm-up and it idled down perfect. Then made minor adjustment to the idle screws. Blowing out the idle circuit cleared up the
problem. Might work if idle circuit is plugged. No promises but a cheap easy fix if it is. JWID
--
Larry
78 Royale w/500 Caddy
Menomonie, WI.
 
A couple of years ago I was working on restarting a 1978-403 that had sat for 19 years. After starting it, it ran very poorly and had similar
running lean problems after warm up. I went to an engine replacment site where Dick Paterson was working and in passing I asked him what I should do
about the carb. His e suggestion was to fill the carb on the engine with 100% carb cleaner and let it sit for a day or so. I did that and after
cranking enough to get some of the cleaner out, the engine started and it runs perfectly. I wish my 455 started and ran that great.

You might want to try that.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
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