Piston stops pumping but motor doesn't stop...burned belt

I have an oiless 33 gallon compressor not more than 2 years old and only used sparingly so far.


The other day I noticed it smelled of burnt rubber so I removed the cowling to inspect. The belt had several burned/melted spots and dry rubber shavings around the flywheel.

I turned it on to see what was going on...initially all is well but after the piston pumps for ten times, it stops. However, the electric motor continues to spin which creates the burn spots on the belt. The tank is not even close to being filled to max when this happens...in fact, it was below 60 psi. Any ideas??

_____________________
Bill says...

Brian, when I first started reading your post, I thought you might have a pressure switch problem. But then I read that the motor keeps running, it's the pump that stops. If the pressure switch shut off the compressor prematurely, it would, too, have cut the power to the motor as well and the motor should have stopped.

I don't know how you can count that the pump has cycled 10 times, as they pump pretty quickly.

Regardless, I surmise that you have a heat related problem, and that might be seizing of the pump.

I can think of no other condition where you would get intermittent seizing of the pump.

It would be confirmation to know that you had to wait for the pump to cool down before it would run again, even for that 10 count.

Cheers,

Bill

Comments for Piston stops pumping but motor doesn't stop...burned belt

Click here to add your own comments

May 10, 2011
Need help
by: Brian

The pump is not seizing...it pumps and then shuts down slowly like it is being told to do so but the electric motor is not receiving the same signal to shut it down so it continues to spin and burn the belt. I turn the switch off and then back on and the process repeats itself with the same result. I guess I can start replacing parts like the pressure switch and check valve. At a loss!!

______________________
Brian, it's the motor that drives the pump. If the pump is slowing, it's encountering additional load from somewhere.

If it's not heat related, then it may be the check valve going into the tank. If it becomes to hard to open against the tank pressure, the back pressure might cause the pump to slow. Not likely but possible. Pull the check valve and check it out.

You have a pump problem, not a pressure switch problem.

May 09, 2011
not thermal I think
by: Brian

I meant approx. ten cycles since I can see the flywheel and piston moving. Once the flywheel and piston stops (don't know what is causing it to do so), the electric motor is not shutting down and thus burning up my belt. This isn't a heat issue as it happened when I 1st turned it on after sitting for two weeks...I think. Mdl# Craftsman 919.167620.

Click here to add your own comments

Add your own question or comment. It's easy to do. How? Simply click here to return to Craftsman Compressor Issues.

921.166360 runs for short bursts 3-5 seconds then shuts down

by mike
(michigan)

runs for short bursts 3-5 seconds then shuts down - won't build pressure
___________________________

Mike, make sure that you have clean power to the compressor. If power is siphoned off to other appliances when the air compressor is trying to run, this could cause this issue.

Assuming you have clean power, drain the tank to zero PSI. Will it start and run now?

Assuming it does not, when it cycles, is the pressure switch turning power on and off to the motor or, when it goes off, is the power to the motor still flowing?

Answers needed for further help. Post as a comment here, please.

Cheers,

Bill

Click here to post comments

Add your own question or comment. It's easy to do. How? Simply click here to return to Craftsman Compressor Issues.

Removing nut from bottom of Craftsman compressor tank

by John Pforzheimer
(Sarasota, FL)

Compressor tank drain nut

Compressor tank drain nut

I got a used Craftsman compressor. The drain valve is broken off inside the large nut.
How can I get the nut out? I tried heat and Break Free, but it wont budge. Any tips?
Thanks
John

Comments for Removing nut from bottom of Craftsman compressor tank

Click here to add your own comments

Dec 07, 2013
drain valve
by: Doug in s.d.ca

You don't say what you've tried in terms of the tool(s) you used.

In my experience, that is probably either 14mm or maybe 9/16". Try a box wrench, if you haven't.

If it still won't break loose, then try an impact wrench with appropriate socket.

Most any automotive shop could get it loose for you if you don't have impact gun.

Click here to add your own comments

Add your own question or comment. It's easy to do. How? Simply click here to return to Craftsman Compressor Issues.

Find replacement Check Valve for 919.156* Series

by James Quaid
(Cave Creek, AZ, US)

I'm looking for a discontinued item from Sears. It's for a model # 919.156580 > 919.156.880 series compressor. The old check valve is being soaked in W-40 at the moment. Most of the corrosion has been removed and I'm going to pull it apart to see what the valve seat looks like.

Comments for Find replacement Check Valve for 919.156* Series

Click here to add your own comments

Jan 03, 2014
Plumb New Valve Suggestion
by: JQ

Thanks, an associate of mine made the same suggestion. I just have to find a check valve with the same specs and then deal with the plumbing. Shortening the tubing won't be a big deal..

Jan 02, 2014
check valve
by: Doug in s.d.ca

Yer prolly not gonna find one;
Best bet is a repair shop to try to get something adaptable to your machine.

There's only so many possible permutations.

As you know, the old one may be ok or repairable.
_______________
Or, replace the tank check valve assembly entirely with another brand. As long as the air lines are oriented correctly, your unloader is plumbed correctly, the system doesn't care what brand you use. All of what is necessary to replace the entire check valve assembly is available from a good plumbing supply shop in brass and copper.

Click here to add your own comments

Add your own question or comment. It's easy to do. How? Simply click here to return to Craftsman Compressor Issues.

craftsman 2 hp century 220 volt comp quit

by Fred
(Middletown, Ohio, USA)

I bought a craftsman 2 hp 220 volt air compressor used 1981 in great condition, brought it home, plug it in correct voltage, ran for about 10 seconds then quit.

Thermal overload did not kick, breaker did not trip, could this be the contacts on the motor?

Comments for craftsman 2 hp century 220 volt comp quit

Click here to add your own comments

Dec 13, 2013
contacts
by: Doug in s.d.ca

Not likely. You'd expect to hear it try to start (buzz or hum or something) even if the start switch was bad.

I'd be first verifying the power supply circuit, especially if it is new.

Circuit breakers sometimes appear untripped when they have tripped. Poor connections anywhere can quickly overheat and go open.
_______________
As well as Doug's fine advice, have a look at the troubleshooting article about why air compressor won't start for a list of other things to check.

B.

Click here to add your own comments

Add your own question or comment. It's easy to do. How? Simply click here to return to Craftsman Compressor Issues.