[SEL] Fuel Intake Compensating Valve Theory/Question

[jbcast at charter.net]

> I too have a question about the compensating air valve on the Fairbanks 
> engines. We have a stand alone Fairbanks engine and air compressor used 
> to build air pressure to start the big Fairbanks at our show grounds.
> We have cranked on that that little engine until there are several 
> bloody hands. Then one of us will finally recall that the throttle plate 
> has to be manually held closed or near closed. It will start instantly 
> then. At rest the governor spring will hold the throttle plate wide 
> open, and I cannot imagine FM intended as part of the starting procedure 
> to hold the throttle closed manually.
> Can you venture a guess as to what might be wrong so we might correct 
> the problem?
> Curt Holland

Curt, we have a FM running a compressor for starting air also. This one will start by placing your hand over the carb as a choke. If yours doesn't start like this it may be weak ignition. When you throttle it down you're creatiung a vacuum, it's easier to fire a plug in a vacuum than under full compression. Does it have an impulse mag? Check the fire while cranking, should jump a 1/4" gap.
J.B. Castagnos