Date:         Fri, 28 Oct 1994 21:18:21 -0800 (PDT)
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         John Ritchie <ritchiej@ucs.orst.edu>
Subject:      Re: More carb troubles


Chris writes:
> 
> Well, Vroomhilda is giving me more trouble. Situation runs like this:

If I remember right, Vroomhilda is a `73? or so bus...?

> 
> When I start it first thing on a cold morning, it runs great. Idles smooth,
> 	pulls away smooth.
> 
> Runs OK for about 5 minutes. After that, it runs OK at speed, but when
> 	I step off the gas, it dies immediately. Just like I turn the
> 	key off.
> 
> After another 10 minutes, it starts running OK again. Idles, etc. This
> 	is usually right when I get to work. 
> 
> I thought initially that it may be the choke, but it seems to be operating
> 	OK. Mabye (being mexican) it is built for warmer climes, and
> 	unloads too quickly? If I turn it richer, it is impossible to
> 	drive until it warms up for five minutes or so. Too long.
> 
> Is there any way to make the choke unload more slowly? I have thought of
> putting a resistor in line with it, and adjusting it to change the voltage
> across the heater coil. Measure the heater current, then decrease it ten
> or fifteen percent?
> 
> Could it be something else? Mabye I just need to clean out those carb heater
> pipes? 
> 

I've had this problem every winter on my `74 bus too, that it'll idle pretty
well once it starts running well... wait, is that circular reasoning?  but
then, after a few minutes of driving it'll idle really crappy.  I've found,
though, that if I shut the engine off for a few minutes, then start it again
it'll run just fine but otherwise it doesn't get "warm" enough to idle
correctly for many miles (quotes because I'm assuming it's a heat problem).

What I've attributed this to is carburetor icing.  It happened when I
had the stock Solexes and now with the Dellortos, but maybe not as bad.  The
Dellortos don't have either chokes or the heated-air recycling tube thingy
that the Solex setup had (mine was broken anyway).  The reason I think it's
better with the Dells, even without choke and carb heater, is that the intake
manifolds are so much bigger, thus less airflow constriction, thus less 
refrigerator effect (can you tell I've never had a physics class?).  Besides,
as I said, my Solex stuff never really worked right.

If my theory is right, then you should be able to improve the situation 
by cleaning out those carb heater pipes, if you're talking about the same 
thing I think you are.  Adjusting the choke may help too, but instead of 
wiring in a resistor or so, I'd try just adjusting the chokes back a bit 
so they open a bit later, as long as they still open fully.

Hope this was of some help, or at least not too confusing.  Let us know 
what you find out.

John
and `74 bus (sitting outside in the rain, filling with water, gradually
rusting... life's tough when you're an Oregon bus)