Bostitch Air Compressor Won't Build Pressure

This article will serve as a hub for all Bostitch air compressor not building pressure, related issues. It’s a very common problem for Bostitch air compressor will not build pressure, and so, this article will present the reasons why this occurs, along with current reader questions and answers.

Why My Bostitch Air Compressor Won’t Build Pressure
Fixing a Bostitch Air Compressor That Won’t Build Pressure
Additional Bostitch Pages
Reader Questions & Responses – Bostitch Compressor Won’t Build Pressure

Why My Bostitch Air Compressor Won’t Build Pressure

The most likely reasons why your Bostitch air compressor won’t build pressure are:

Bostitch Air Compressor Intake Valve Failing

If it is the intake valve that has failed, then the compressor will draw air in on one cycle, but then that air will blow right back out the intake valve.

Bostitch Air Compressor Pump Pressure Valve Failing

A fault pressure valve will cause air to flow into the tank through the pressure valve on the compression stroke but then be drawn right back out of the tank as the piston cycle to try and draw more air in through the intake valve.

Bostitch Air Compressor Gasket Failure

The flow path of the intake air inside the pump head is often only separated from the flow path of the pressurized air to the tank by a gasket. It is possible that your compressor is working fine, but as it is cycling, the air is flowing back and forth across a failed gasket inside the pump instead of being forced into the tank.

Bostitch Air Compressor Piston Seal Failure

If the rings are defective, the pumps will lose pressure and compression strength. This can also reduce the pump’s efficiency to optimize the production of compressed air.

Bostitch Air Compressor Tank Check Valve is Compromised

When the tank check valve becomes defective, the discharge head of the pump will receive a high pressure of air. It will affect the pump’s motor might and stop it from restarting anytime the tank is full.

Fixing a Bostitch Air Compressor That Won’t Build Pressure

Please visit our Why An Air Compressor Won’t Build Pressure & How To Fix A Compressor Not Building Pressure guide for detailed information on each, along with how to conduct the necessary checks! If you’re wondering why your air compressor won’t stop running, we also have a guide on this!

Additional Bostitch Pages

Reader Questions & Responses – Bostitch Compressor Won’t Build Pressure

Bostitch CAP 60P Air Compressor Has Low Air Pressure

Question

My CAP60P ran perfectly until the other day. Now it will not get above 20psi and the motor continues to run.

Cannot find any air leaks except in one place but not sure what the function of the Rilsan tube is.

It is blowing air where it enters the pressure switch and if I recall it has always done this so I suspect it may be some kind of safety device.

Compressors are 4 years old and only have about 4 hrs use. It has held the 20 lbs of pressure in the tank now for 24 hrs.

Response

The Rilsan tube is a brand name flexible tube manufactured/supplied by mebraplastik.com.

On your compressor, I suspect this tube runs from where the airline to the tank from the pump head reaches the tank and the pressure switch?

Bostitich CAP60P compressor parts diagram

That this has leaked all along might be a problem, Leon.

If the air is blowing out of the unloader valve and not out of the hole in the tube, then your tank check valve is leaking air out through the pressure switch, and that may have recently increased to the point where the compressor cannot overcome the leak.

If the air is actually blowing out of the tube itself, then I would surmise that the tube has failed.

First, stop the air leak, and then, if the lack of pressure build continues, add a comment here and please add a photo of your compressor.

If you review the troubleshooting page you’ll see pages about why air compressors run but don’t build pressure.

My Bostitch CWC200ST 3hp 4gal Twin Tank Air Compressor Won’t Build Enough Pressure

Question

CWC200ST 3hp 4gal. twin tank. The compressor is plugged into a power pole on a 20 amp breaker, no extension cord is in use.

With the tank empty turn the compressor on, it will reach about 30 psi and then will throw the reset. Wait a couple of minutes push reset and it will them pressure up to around 60 psi and throw the reset again. Does this again at around 90 psi and then finally reaches 125 or 130 psi at normal shutoff.

I have checked and adjusted the pressure switch, have checked the pressure relief valve, and checked the valve that allows air into the tank.

I don’t know what to do. It should not be the capacitors or pressure switch as it starts fine, and the pressure switch also shuts it off around 130 psi.

I started to bypass the reset but did not want to ruin something else. This has been in the shop twice and they say they can’t find what’s wrong. Any help would be much appreciated. Thanks, Tommy

Response

Tommy, if the start/run capacitor on your is weak, that could account for the compressor issues you are facing.

The start/run cap builds a bit of a charge which is used to get the motor going, but the motor lacks the power supply needed to keep going against a building pressure, the motor overheats as it’s struggling, and as a result, it kicks off the compressor motor thermal reset.

See the page about checking your caps on this site, and see if that is the problem, won’t you? Then add a comment if you still need some help.

OL 195 Bostitch Upright Air Compressor Won’t Build Pressure

Question

I have OL 195 Bostitch.

It was not building pressure much at all.

Opened and found a flapper valve broken on one.

Bought a retro kit and changed it over to a new kind, piston head, gaskets, head, etc.

Now it builds to 20_30 psi and just runs. Maybe check the valve, or pressure switch, what else?

Response

The Bostitch model number OL195 refers to the pump on the compressor, Steve.

I believe the model is the Bostitch CAP60OF.

Regardless, it is doubtful that it is the pressure switch, Steve, as the purpose of that switch is to turn the air compressor on when the pressure in the tank is low enough and to turn it off when the pressure in the compressor tank gets high enough.

In between those two pressure settings the pressure switch does not provide any function except to let the power flow to the motor circuit.

If the compressor is running and getting up to 20-30 PSI and no higher pressure, then the typical compressor problems are plugged intake filter, damaged intake valve, damaged pressure valve, piston seals or, and what is most likely in your case I would guess, is the internal gasket(s) are leaking.

Did you replace all gaskets with new, or use the old

?Let us know, will you?

CAP-60P-OF Bostitch Air Compressor Not Build Pressure

Question

I have a Bostitch CAP60P-OF, which will not build much pressure past 20 psi, and runs forever.

I removed the pump head & intake valve, which look good to my knowledge, reassembled it, and the same issues.

I also removed the aluminum tube and used another air source and pumped air directly into the tank at the check valve, pressure went up as expected. I then removed the aluminum tube, and I could hold my finger over the exit port indefinitely.

I would like to know the possible cause, and where I can purchase a rebuild kit. Thanks for the help, Jeff Smith

Response

Hello Jeff… from the sounds of it your compressor valves are compromised, you may have a piston seal wear issue, or you may have a gasket that lets go at 20 PSI, and instead of air going into the tank with force, as soon as there is backpressure, the air simply cycles inside the pump.

As to parts, if you search “compressor parts for Bostitch CAP60P-OF” as I just did, you will find a number of sources.

Maybe you could upload a photo or two of this model of Bostitch? Thanks.

CAP60P-OF Bostitch Pancake Compressor Won’t Build Enough Pressure

Question

I have done a lot of reading on this compressor; seems like a nightmare unit for the most part. Since I already own it, I might as well fix the darn thing.

This started with the valves in the head breaking, so I rebuilt the head with new gaskets, sleeves, rings, and valves. Then the regulator developed a leak; replaced it. Now it runs and runs and won’t build past 50 PSI.

I suspect an issue with the pressure switch. When I disconnect the small black tube from the check valve I get good pressure shooting out; as expected. When I close off the outlet to the pressure switch it starts building pressure again.

Bostitch exploded diagram of CAP 60 compressor

Obviously, it is dangerous to run without the pressure switch, so that is not an option. I am baffled by what is happening though; I thought the pressure switch only served as an upper limit shut-off?

Where do I go from here? Any suggestions?

Thanks.
Derek, from Des Moines Iowa

Response

Sorry, you’re having so many problems with your Bostitch air compressor Derek.

Try this. Empty the tank with the compressor off then remove, clean and replace the tank check valve.

Reassemble and test. Any change?

Please let us know as a comment here and maybe upload a photo or two of your Bostitch?

Thanks, Bill

Question

Same compressor, same problem, I also thought it was a leak in the pressure switch because I thought I heard air escaping there. while cleaning the switch the little V-shaped spring fell out and I can’t figure out how to reassemble it. Can you help me out?

Charlie Webber.

Response

Charlie, I’m afraid those things are nearly impossible to re-assemble without having or making tools to do it. They’re pretty cheap, so just replace them.
Regarding the escaping air, they are supposed to do that, but the check valve is supposed to stop the “leak” almost immediately.
You may find this page helpful:
https://www.about-air-compressors.com/buying-a-compressor-pressure-switch/

Good luck. Doug from s.d.ca

Response

There are pages on this site about how to reassemble a pressure switch. Here’s one:

https://www.about-air-compressors.com/putting-a-pressure-switch-back-together/ and another is here:

https://www.about-air-compressors.com/put-my-pressure-switch-back-together-again/.

But… as Doug says, the process is hardly worth the aggravation as an off-brand, online, pressure switch pricing is fairly cheap, Bill.

Oil Free Bostitch Pancake Air Compressor Will Not Build Pressure

Question

Oil free compressor does not build any pressure or very little? My Bostitch pancake air compressor started by not shutting off when it hit the designated air pressure (continuously ran unless you manually shut it off), but now it turns on and sounds weird and does not build any pressure or very little. What would you say is wrong?

Response

Ben, first off, that the compressor didn’t shut off at normal cut-out pressure and you had to shut it off manually suggests the pressure switch has failed.

The weird sound you are hearing might be intake valves, pressure valves, blown gasket, motor failing, pump mechanical issue… it is pretty hard to tell from here.

When you say “but now it turns on and sounds weird” do you mean that it is cutting in at the normal pressure setting, the compressor is running at the point, but no air pressure build-up in the tank at all?

Can you please post a comment with more details?

Bostitch 6 Gallon Oilless Air Compressor Won’t Build Pressure Above 50-60 PSI

Question

My Bostitch 6gal oilless air compressor will run fine to around 50 or 60 psi, and then continue to run without gaining more than a couple of psi.

No audible air leaking and the tank continues to run just as before.

After a couple of minutes, I turn it off, drain it, then repeat and get the same result.

60 psi is about the max I have gotten. Any thoughts would be greatly appreciated as this compressor is very pricey and too expensive to replace. I’ve also taken the piston head apart and all the air valves are fine.

Response

Jeff, good that you checked the valves. Glad also that they are fine. There are other issues relating to air compressors that run and don’t build pressure.

Shut it down, empty the tank, remove, clean, and replace the tank check valve. Any change?

Assuming that the power supply hasn’t changed, you may be experiencing a pressure-related gasket failure, or you might still be having a valve fail under load.

See the site map page, under the Troubleshooting category, for links to more info on why an air compressor will run and not build pressure.

CAP60P Bostitch Air Compressor Won’t Build Pressure

Question

Bostitch model# CAP60P – OF

Unit won’t build pressure.

The main supply line to the tank at the non-return valve gets real hot.

The compressor also has a higher pitch sound. The non-return valve seems to be working. I’m wondering if it’s the valve plate assembly at the head?

Lane

Response

Lane, if you have air huffing out of the intake port on the pump head, then, for sure, you have a valve leak. Air is bleeding out fast enough that the compressor tank pressure can’t build past a certain point.

The pressure valve failing could be the cause, as well.

All compressor airlines from the pump head to the tank get too hot to touch. That’s why they are made of metal, so that symptom may not provide any clue.

Don’t know about the sound change, though that might be because of the valve issues, or an internal gasket leak at a certain pressure, or it could be that the compressor is running too long and overheating… it’s supposed to shut off fairly quickly after the pressure switch turns it on.

To correct these you will need to tear down the pump. You might as well have a valve kit and gasket kit on hand when you do. If the valves are at fault, you will have the valve kit ready. The process of tearing down will likely destroy any gaskets, so not only will you not be able to tell if they were at fault, but you will need to replace them anyway, I suspect.

Bostitch OL 195 Air Compressor Not Building Pressure

Question

I have OL 195 Bostitch.

It was not building pressure much at all.

Opened and found a flapper valve broken on one.

Bought a retro kit and changed it over to a new kind, piston head, gaskets, head, etc.

Now it builds to 20_30 psi and just runs. Maybe check the valve, or pressure switch, what else ?

Response

The Bostitch model number OL195 refers to the pump on the compressor, Steve.

I believe the model is the Bostitch CAP60OF.

In between those two pressure settings the pressure switch does not provide any function except to let the power flow to the motor circuit.

If the compressor is running and getting up to 20-30 PSI and no higher pressure, then the typical compressor problems are plugged intake filter, damaged intake valve, damaged pressure valve, piston seals, and what is most likely in your case I would guess, is the internal gasket(s) are leaking.

Did you replace all gaskets with new, or use the old

Let us know, will you?