What about an air leak in the carb?
On Wed, 9 May 2001, Allen Jones wrote:
> This is kind of off topic (hope I don't get in trouble, but the list is
> very, very helpful), but it does pertain to an old 1/4 ton truck!
>
> I have a fresh overhaul on my '55 M38A1 (it's the military JC5 with a 134 ci
> 4 cylinder) including fresh overhaul on carb, distributor, fuel pump, new
> wires, etc. - bone stock setup. The weird thing is that I have to leave the
> choke on (alot) all the time (after being warmed up) to get it to run good
> which leads me to believe it's fuel starved. BUT! The fuel pump checks out
> for both pressure and flow. When I pull the top of the carb off, the bowl
> is full of fuel. Intake vacuum checks out with normal vacuum and no leaks
> (no intake manifold - the carb bolts directly to the head). The timing is
> set at stock and the mechanical advance seems to work fine. The valve lash
> checks out fine. Compression is normal. I've put the carb on a carb
> machine and the power valve starts to operate at 7 inches of vacuum (which
> should be ok). I can also peek down in the carb throat and see gas
> squirting in when I goose the carb (the carb was sent through a sonic
> cleaner when overhauled). I'm stumpted. Any suggestions would be greatly
> appreciated. I imagine I've missed something here. Or is it normal with
> some vehicles to run around all the time with the choke on? It's not that
> cold here in Seattle....
>
> Thanks.
>
> Allen in Seattle
> '50 3100
> '55 M38A1
> oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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