Re: ihc-digest V5 #133

[Ted Borck <tborck@domain.elided>]

> Date: Tue, 20 Jan 1998 05:13:26 GMT
> From: jlandry@domain.elided (John A. Landry)
> Subject: Re: Backfire....
> 
> Ckhansen <Ckhansen@domain.elided> scribbled in the sand:
> 
> >OK....I have something I can't figure out.  My 76 Scout with a 345 2 barrel
> >backfires occasionally just on startup.   Timing is good, recent tuneup, new
> >fuel pump and filter.  Runs good otherwise.  Any ideas??
> 
> Chris,
> 
> 1. Check the ignition timing.  It may be too far advanced.  If it shows as
> being correct, don't rule out that it still isn't right.  There's always the
> slim possibility that harmonic balancer on the crankshaft has slipped giving
> an incorrect (retarded) ignition timing.
> 
> 2. Look for *intake leaks...* especially loose or cracked vacuum hoses.

<snip>

> Good luck,
> 
> John

Chris,

Your carburetor probably has a zillion miles on it, and is leaking 
(vacume leak) around the throttle butterfly shaft.

To check, squirt some oil (while engine is warm and idling) where the 
shaft ends protrude from the carb throttle body, and see if you get any 
smoke when you blip the throttle.

OR take a small hose (to use as a stethoscope) place one end against the
carb throttle body shaft, and then against the carb throttle body where
the shaft doesn't protrude, and determine if there is any difference in
sound(s).

I had this problem, bought a new carb and the problem went away (better 
idle, better gas mileage too).

Hopes this helps

Ted Borck	tborck@domain.elided