>>
>> Sometimes my electric fuel pump although "chattering happily"appears to be
>> incapable of self priming.=A0 If the engine is cranked (and the mechanical
>pump
>> is used) for a few seconds the electric pump=A0 then primes and thereon
>> maintains pressure unaided.=A0
>
>
>Not heard of this one before. The only guess I could make would be dust in
the
>pump. I did test a Facet pump to see what height it would self prime and
>achieved about 4 feet. Only other thing that would stop it would be back
>pressure. If the carb was full the system wouldn't accept any fresh fuel
so it
>would not then self prime. Could that be the answer?
I've been meaning to take one of these pumps apart and see how
they're made. I think it quite likely that they have "reed valves"
which are very thin, flat pieces of sheet metal that seal against
really neat . . .when they work.
One way to check is hook a 4-5 foot piece of clear tubing (like
tygon) to pump inlet. Submerge end of tube in paint thinner (aka
charcoal lighter, petroleum distilates, cleaning solvent, etc.).
Hook up pump to make it fill tubing and clear air with a good flow
out the exit.
Disconnect electrical power then raise the pump while keeping the
end of the tubing submerged in liquid. Hold it at a height of
about 4' above the liquid and watch to see if it begins to leak
back. This will be obvious as the air collumn builds on top of
a decending liquid level.
If the pump cannot HOLD a 4' head, then it's unlikely to prime
itself at a 4' head.
Bob . . .
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