The compressor works fine up to 90psi. Its an oil less electric compressor.
At 90 psi, with the cover off, I noticed the piston was slowing down and eventually stops.
The engine keeps running. The belt is trying to push a stopped piston and this is the reason why the belt is burning.
Its trying to force the piston but at 90 psi it does not want to move. I just replaced the check valve. This did not help. What do you think is wrong.
Lonnie, if this were my compressor I would be looking at the valves, and in particular, the high pressure valve to the tank.
It sounds like the tank pressure is back loading the line to the valve, and since the valve may not be working right, the piston cannot easily drive air past it into that line, and it stalls the piston, but the motor doesn’t slow.
Might also be the pump itself causing the problem, but I’d be checking the valves first.
Where is this part on the schematic
Thanks Bill for your quick reply.
The model # of the compressor is 919.167620.
Can I trouble you to look at this link which is the schematic of my compressor.
I do not understand what part you are saying is suspect. Where is this high pressure valve in the diagram. Thanks again.
The valves are on the valve plate #85, and if they are the problem, there should be some evidence (broken / jammed / debris )if you can get to them.
I will take the pump apart this weekend
I will take it apart this weekend and see what it looks like.Thanks again.
Do you know of a repair manual that can provide the torque settings when putting it back. Can I call Sears?
Yep, Sears is the source, unless a kind reader has the info for you.
Valves seem ok
I took a look at the valves.Everything looks brand new. I put the valve plate back on. The compressor used to go to 90 psi before the piston slowed down and I smelled burnt rubber. After putting the valve plate back on, the compressor only goes to 30 psi now. The piston slows down, the wheel that turns the belt gest very hot and this is what is burning the belt.
The belt definitely looks burnt but does not appear to slip. Can the problem now be the belt? Maybe the belt is not tight enough to move the piston hard enough, what do you think?
Lonnie, your “adjustment” of the valves by opening and closing the head seems to have affected the operation of the compressor. You didn’t touch the belt, so, why would the output change?
I doubt it’s the belt. Do you get 1/4″-1/2″ play both sides when you push or pull on the belt between the sheaves? Somewhere around there is a typical belt tightness.
I still feel the problem is in the pump, or possibly the check valve into the tank, if it is not a mechanical issue with the pump drive / piston / cylinder itself.
Keep us posted Lonnie. I expect someone else will chime in soon with other suggestions.
Still getting burnt rubber
I have no idea why removing the head and plate and then putting everything back would change the max pressure I can get from 90psi down to 30 psi.
The valves and plate look brand new.I am not sure if you are supposed to but I flipped the valves back to front. That is, I removed each valve and turned them around. This made no difference.
The small wheel the belt is on gets really hot. This is whats burnig the belt. I have no idea why only this piece is getting hot.
When the psi reaches 30 psi ,which is very quickly, I can see the piston slow down.
Did you get a chance to pull, clean, and replace the check valve?
Yes, check valve replaced
The check valve looked good but I installed a brand new one anyways. no difference.
Finally fixed burning rubber belt on compressor
Finally fixed the problem!
The top wheel that the belt is on when adjusted, tightens the belt. Once the tension was correct, magically the compression was back at 150 psi and the center wheel stopped heating. Much time was spent and its hard to believe a loose belt would cause so much issues.
Man, that seems like a heck of a journey. Glad it worked out.
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