Re: Carb Woes

[jlandry@domain.elided (John A. Landry)]

On Tue, 4 Nov 1997 08:33:06 -0500 (EST), you wrote:

>I have a cold running problem that I need help on.  Every morning my '75
>Scout II starts fine and warms up well.  I think it takes too long to warm
>up (~15 after being run the night before and it's not that cold yet), but
>that is probably the average for most engines this size (345).  Anyway,
>after it kicks down and is idling smoothly I put it into drive and as soon
>as I step on the accelerator it stalls.  I get out, play with the choke
>butterfly, no problems I can see, get back in, start it and it is fine.
>It does this every morning since it started to get cold.  Even after it is
>totally warmed up I have to keep one foot on the gas and one on the brake
>at every light on my way to work.  Is there any tricks to getting it to
>run better in the cold?  Or does it sound like something is wrong with the
>accelerator pump etc.  The gas tank, fuel lines, fuel pump and filter have
>all been recently replaced, so if there is a problem it has to be in the
>carb.
>
>I have doused the choke and all moving parts in carb cleaner and
>everything seems to be working fine.
>
>Any help on this frustrating problem would be appreciated.

Bill,

This sounds suspiciously to me like maybe one of the following scenarios...

A. My first guess is that in fact you do have a choke problem of sorts.
You need to remember that the choke consists of two parts.  One part closes
a large plate (aka "butterfly") over the carburetor intake and the other
part is the fast idle cam.  Of course the function of the choke plate is to
block incoming air and cause an enrichening of the air / fuel mixture.  The
rich mixture is needed when the engine is cold, because the atomized fuel
tends to fall out of suspension in the cold intake manifold passages and
burns inefficiently.  The fast idle cam keeps the idle rpm high to help
overcome the typical rough running condition of a cold engine.

Just because the engine is idling at a normal "curb idle" speed, it doesn't
mean that the choke plate isn't sticking partially closed somehow, thus
needlessly enrichening the air / fuel mixture.  An overly rich mixture will
cause the engine to perform much like it's too lean.  When you try to
accelerate with an overly rich mixture, the engine will bog down and die.

You seem to imply that when you've this problem, you've gotten out and
maybe fiddled with the carb linkage.  Upon getting back in the truck and
restarting the engine, it runs fine.  This sure smells like something was
stuck... but I could be wrong.

B. Maybe somehow you have a problem with the accelerator pump?  Maybe it's
temporarily sticking in the down position until you tinker with the carb.

When was the last time the carburetor was completely cleaned, rebuilt and
adjusted?  Maybe it's time?

Good luck,

John


>
>
>Thanks Again,
>
>Bill Wisser
>

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