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Re: Dumb, but important question

Subject: Re: Dumb, but important question
From: (Denise Thorpe)
Date: Mon, 20 Nov 95 09:52:32 PST
Frank Sperling III asked:

> My 79 B has begun deiseling for 5-10 seconds after I turn it off.  To 
> make matters worse, it recently has stopped this deiseling when it 
> emits a LOUD backfire.
> Here's the dumb question...what do I adjust to stop this?  The timing 
> (advance, retard it?)...lean out the fuel mixture (turn the screw in 
> the middle of the Zenith diaphram clockwise or counter clockwise?)

A '79 B designed to run on low octane, unleaded fuel has a natural tendency
to diesel, so it has an anti-run-on valve.  The valve is located on the
passenger side firewall.  It's the thing with the vacuum line strung across
the engine compartment so that it can't be avoided when doing anything 
under the hood so the plastic nipple on the valve always breaks off and
the whole d**n valve has to be replaced.  I forget exactly how it works,
but it's obviously not working if it's still there.  If it's not there,
then the dieseling can be slowed down by retarding the timing and/or 
leaning out the mixture.

Backfires are caused by many things including running too lean.  A '79 B
has another amusing valve, the gulp valve, that can cause backfires if it
has gone bad.  This valve is part of the air injection system.  My advice
is to get a pre-smog car.

Denise Thorpe

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