by Frank
(Shawnee, KS, USA)

Bostitch CAP60P-OF does not build up pressure? Small single stage compressor. Runs fine. Built in 2006. Does not build up pressure.

I think it is either the reed valves in the piston top, the reed valves in the head, or the rubber ring around the piston. But the reed valves look good. The rubber ring could be a little harder than it should be. The rubber ring is not torn. I don’t know how soft it should be.

The reed valves seem to look OK. But I don’t know what else could be wrong. The tank is tight. The connections and drain plug are tight. I can take the drain plug loose and feel pressure coming out, but the pressure is very low. I can easily stop the air from coming out with my finger. The gauges never read any pressure.

I am inclined to replace the reed valves and the rubber ring, but I’m sure there isn’t a problem with all of that. What is the most likely cause of the problem?

Thank You,

Frank
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Frank, I’ll take your word that the valves are good. I don’t think it would be the piston seal.

Wish you had uploaded a photo or two of your Bostitch Cap 60 F compressor as I haven’t been able to find one.

However, I suspect that it’s a gasket in the pump letting go when the pressure reaches a certain level, and you have air flowing back and forth inside the pump, and not into the tank, based on what you have said.

You will have to take the pump apart to inspect the valves, and in the process you may damage gaskets so if that is the plan, have a gasket kit (and a valve kit?) handy.