[T3] The Winter Gas

Jim Adney jadney at vwtype3.org
Sun Oct 20 21:58:17 PDT 2013


On 20 Oct 2013 at 19:17, Keith Park wrote:

> I got nothing under 2500 RPM or so now!  

I think you're jumping to the conclusion that the gas is the problem. 
I suspect there are lots of other possibilities that simply relate to 
the fact that the car is getting colder. How about any of the 
following?

The check valves in the fuel pump get hard and don't seal on the 
upstroke, so they bleed pressure back. This would be worse at lower 
rpm, when the time spent on the upstroke is longest. They also get 
continually cooled by incoming cold gas from the tank, so they never 
warm up.

The rubber float valve seals in the carbs get hard and fail to seal 
for the same reason. The float valves leak and overfill the bowls, 
resulting in overrich running and loss of power. This leakage would 
have the greatest effect when normal fuel consumption would be low, 
so this might show up at low rpm.

That's all the occurs to me on the spur of the moment, but people 
more familiar with carbs than I am should be able to come up with 
more. I just wanted to make the point that pointing to the fuel 
alone, especially when no one else sees the same effect, is probably 
missing something.

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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