Bostich CAP60P-OF does not build up pressure?

by Frank
(Shawnee, KS, USA)

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

I suspect, rather, 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.



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Aug 28, 2014
Won't build over 50 psi
by: Bill

I can hear the frustration in your voice.

When you did the checks, are you getting good suction at the intake.

When you pull the line from the pump to the tank, is there good pressure coming out of the pump?

Besides that the Bostitch won't build past 50 PSI, are you hearing or seeing anything new on the compressor?


Aug 27, 2014
Bostitch won't build over 50 psi
by: Tom

My bostich air compressor cap60-of will build 50 pounds pressure and continue to run can not build any more pressure I rebuilt the head new ring and gaskets get the same thing still get 50 pounds pressure I check for leaks can't find any anywhere I don't know what else to do.

Oct 01, 2011
wont auto shut off nor build up psi over 120.
by: charles / grandpops

It simply won't go over 120 psi nor shut off there a way to lessen the psi say from 150 down to 110? Not very good on air compressors but am heck on a chain saw. Any ideas out there? Thanks a lot and have a great day!



Odds are very good that your intake or high pressure valve is pooched, or you have a gasket leak at pressure. Yes, look at the PRESSURE SWITCH page for information on them. Don't recommend this as a solution however, as the problem will only get worse until you won't get air buildup at any pressure.

Aug 08, 2011
found problem
by: Anonymous

I put a little silicon grease on the rubber spring loaded stopper in the 'non return valve' that mounts right on the tank. That allowed the valve to seal between air bursts. It has worked for several days now. But I don't expect it to continue. Probably needs to be replaced.

Jul 31, 2011
Could you explain a bit more Bill?
by: Frank

Thank you Bill!

This is the first time I have ever looked inside a compressor. So all I can say is that the valves "look" good. They aren't broken. They might be bent or... sprung... I just don't know.

You said a gasket in the pump. Does that mean in the head of the compressor? If so, those gaskets there look good. The layers are solidly assembled and I can feel no air coming out. There just doesn't seem to be much else involved. I was wondering about the spring loaded seal that is right on the fitting to the tank. It appears that spring loaded seal has to move back and forth as air is pumped into the tank. If that thing didn't seal, air would escape from the tank into that incoming pressure line. But that seal 'looked' good too.

Would it make any sense to put a layer of oil on the cylinder in an effort to temporarily seal the rubber piston ring and perhaps some oil on the seal I mentioned above?

All I know so far is that something is wrong. I appreciate any advice you provide Bill.


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Model: CAP60PB-OF shuts off before it reaches max psi?

by Larry Goad
(Cheraw, SC USA)

My Bostitch compressor Model: CAP60PB-OF shuts off before it reaches max psi

My compressor (new) shuts off at 100psi (max is supposed to be 135psi) and then kicks in at 95psi. Is there a way to adjust the factory settings to correct this problem or should I return the compressor?

Thanks, Larry
Larry, if the specs for the air compressor show a cut out of 135 PSI, and the compressor is cutting out at 100 PSI, I would suspect that you've got a bum pressure switch, or one that is not set properly at the factory.

If it were me, I wouldn't monkey with settings on a new Bostitch compressor pressure switch, I'd take the compressor back and say give me one that works right, right now!



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Wattage of CAP60P to run with generator?

AT times i would like to operate my CAP60P compressor using and auxiliary portable generator. What is the wattage of the compressor?
I think your air compressor has a 2 HP motor, and if so, 2 HP = 1,491.39974 watts, according to Google's wattage calculator.

Then, you'll want at least 50% more wattage available for the start as the power inrush when the motor tries to start is higher.

50% extra might be perceived as high, but I'd prefer to err on the side of caution rather than under powering the compressor motor with all the of problems that can cause.



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Bostitch will not hold air in the tank?

I have a 6 gal, 1.5 HP oil less Bostitch air coompressure. I t worked great the last time I used it but now it will not hold air in the tank. I can't get any pressure in either gauge. The hoses are not leaking, the tank is intact, the pressure release valve at the bottom is closed off. What could the problem be?
Hi there...

Your question suggests that your compressor is running but I cannot tell from the question whether or not the Bostitch compressor is actually generating compressed air into the tank?

You say the tank will not hold air. That could be a number of things causing that.

First, though, I need to know if when the compressor is running you are seeing pressure increase in the tank?

Post your response as a comment to this thread, please.



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Sep 25, 2012
Air compressor will not hold air
by: Anonymous

thanks for getting back to me. No I cannot see any increase in pressure even though I let the compressor run for 15- 20 minutes. There is no indication of pressure increase in either gauge.
OK, now we know that the compressor is running and the pump is running, but no air is getting into the tank... correct?

Since I don't know how old your air compressor is, the problem may be wear related.

There are a few things to check to try and determine why. First off, remove the intake filter to see if that makes a difference. Likely not, but you might as well see if the intake filter is plugged.

While it is off, then feel near the intake port (without the intake filter) to see if air is being pulled in while the air compressor is running, or if it alternatively being pulled in and then blown out. If the latter, the intake valve is failing or has failed.

Then, go to the troubleshooting section on the site map page, and follow the link to the page about why air compressors run and don't build pressure for more things to check.

Let me know what you have found, and we'll press on trying to resolve your compressor problem.



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