Craftsman 5hp briggs and stratton gas powered belt driven air compressor stalls when pressure builds up?

by john piper
(palm bay, fl, USA)

I have a craftsman 5hp Briggs and Stratton gas powered belt driven air compressor that quits/stalls running when the pressure builds up.

Theres 2 valves that i can manually bleed the air from.


Craftsman 5 HP 20 gallon tank gas powered air compressor


Craftsman 5 HP 20 gallon tank gas powered air compressor


One is fancy w/ some sort of diaphragm coming into it before the valve w/ air supplied from the comp. and the other side of it goes to linkage on the motor which appears to adjusts the governor as needed.

If i leave the leaver on top flipped/tripped were it leaks a little the motor will keep running fine and build up air but once i close it and the air press. gets high the motor instantly stops like its locked up or been turning off like an electric one. the other valve is just a typical high pressure blow off type located just before the hose connector. the motor runs great w/ good compression and the compressor builds up pressure quickly which is why im thinking its the fancy pressure regulator switch…any help will be greatly appreciated

John, I don’t have a gas driven compressor, so I hope that folks out there that do will comment and correct any mistakes I make.

It sounds to me as though your unloader, which is linked to the throttle, needs adjustment. When the air pressure in the tank reaches the normal cut out pressure level, instead of a pressure switch turning the motor off, as it does with an electrically driven compressor motor, it unloads the motor and throttles back on the fuel so the compressor motor slows down but keeps running.

When the pressure in the tank reaches the low pressure cut in, the pressure switch toggles the unloader which adjusts the throttle to increase the revs to speed up the motor, allowing it to handle the increased load as the pump starts pumping air into the tank.

I hope someone has a manual or a how-to to help you adjust this mechanism, John. I have not worked on them myself.


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