That's not a fun sounding story...but I've been thru it too!
The ideas of heat from exhaust, crud in the tank, and checking for a
vented gas cap are worth looking into.
You might also want to carefully check the complete fuel line from tank
to carb for leaks or kinks. I had a wierd problem like this with my 59
way back when (still had the 235 in it), and it wound up being a problem
with the flex line under the cab, where the tank connects to the steel
line that runs up to the front of the truck. I think it was kinked,
blocking fuel flow.
If there is a leak in the line, it can allow the pump to suck air
instead of fuel...but it would also likely cause fuel to leak out.
Vapor lock is when you get vaporized fuel in the lines, instead of
liquid fuel. As was mentioned, heat from exhaust can cause this, as can
heat from the radiator. I've experienced it with most of my trucks over
the past few years, and I think it may have something to do with modern
gasoline being formulated to work with fuel injection...where you have a
fully pressurized fuel system. The new gasoline may be more volatile,
and so it vaporizes and vapor locks more easily...this is just
speculation on my part. Usually, the problem is worse when you start
driving after leaving the truck parked for about 5-10 minutes...you
drive for about a block, then the engine dies. Also, if you are on the
highway, and speed up to pass someone, the engine will start missing
badly and lose power after a few seconds of full throttle running.
Vapor lock will always cure itself if you let the truck sit and cool off
for awhile. But, if you kill the battery trying to start it when there
is no gas in the carb, I can see why you'd need a tow.
Also, don't be surprised if there is something else causing your
problem! Before I had the kinked fuel line, I had similar behavior from
the truck, and discovered a loose wire to the ignition coil...remember,
90% of "carburetor" problems are actually ignition problems!
Jim
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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