Fuel Pump draining Thermoquad

["John Hofstetter" <hofs@domain.elided>]

David, 
For what its worth, in my opinion, there is no way that the fuel line
could be sucking the gas back through the fuel pumps leaky diaphragm
to the tank. The problem you have is very common, evoking my retelling
all too often of the gas in the air filter cover depression. 
The Thermoquad I had on my Terra was the only carb I ever owned that
had the fuel bowls go dry, but I know that others have experienced it
on a variety of carbs.  Actually, for many years, this phenomenon was
the cause of a legend growing up out here in the hot West about Scouts
being very hard to start. I had several friends who always had this
problem and never solved it, except to work around it. You'd pour in
some gas, and away it would go. 

An idea that lingers in the back of my mind is that heat from the
manifold of our hot running IHC's vaporizes much or all, of the gas in
the bowls, and that evaporation over a period of time emptys the bowls
of their remaining gas. 

Regardless of what is causing the problem, an electric fuel pump can
get around it. With the electric pump, you turn on the key, the fuel
bowls fill, and the engine starts. 

Not sure of what use I think this will be to you, but ........
John H.
----------
From: owner-ihc-digest@domain.elided (ihc-digest)
To: ihc-digest@domain.elided
Subject: ihc-digest V6 #829
Date: Wed, May 12, 1999, 10:44 AM


Date: Wed, 12 May 99 10:11:18 -0600
From: David_Luebke@domain.elided
Subject: fuel bowel drainage

       >I'm saying fuel pump.  I have had a similar problem, and it
       was mainly fuel
       pump.  Once the diaphragm goes in the pump, the fuel starts
       leaking back.  This
       also would explain the delay in it starting once it drains
       back-takes a little
       longer to get back up there.  I also rebuilt the carb a little
       while after, and
       it helped even more, but I ended up killing the battery before
       I got the fuel
       pump fixed, and after this, it was much, much better.  I am
       reposting this to the
       digest as well, though, as someone may have a good reason that
       this reasoning is
       wrong!

       The inlet to the fuel bowel is higher than the bowel itself,
       so drain back would have to be caused by a vacaum from the feed
       line to the
       tank.   I know there is fuel in the line at the input to the
       pump.   My tank is open to air at the fuel neck.   Would this
       be possible?

       My fuel pump is realitily new, maybe 15 k miles  over 6 years
       old,  can the diaphragm go that quickly?