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Discussion Starter · #1 · (Edited)
OK, here are the details. Porter Cable cplc7060v-1 7hp standup air compressor. I got this from a friend who owns a cabinet shop and this was a "dead" machine. (I actually needed it for the tank to replace a tank that developed a leak). Anyways, I wanted to see just why was this machine dead. I plugged it in and hit the switch and it had a horrible knock on the top end. It was so loud, I thought it was about to come apart. I tore the top end off and it was just all kinds of gunked up with carbon. I cleaned it up including the reed valves and the top of the pistons, ordered new gaskets and put it back together.

Started it up again and it purred.... until it got to around 35psi and the motor started surging as if it were having a hard time turning the pump and then it popped the CB on the motor. Let it cool off, reset the breaker and turned it back on only for it to barely make 1 revolution and stopped. I immediately turned the switch back off to prevent it from popping again. I could also hear air escaping out around the air intake on the head.

I immediately thought it was the check valve and put one on order, meanwhile, I took the old one off of my original tank and put it on and got the same result. A few days later, the one I ordered came in, I replaced the replacement and again got the same results. As a side note, the replacement valve and the replacements replacement valve stopped the air from escaping out the air intake and it does hold the air it pumped in. It just will not go any further than 40psi.

Just to clarify, the pump wants to pump, it just can't because of the back pressure I am assuming it has on the pistons. I even attempted to turn the pump by hand and it would not budge, but the motor will run forever with the belt off.

Any thoughts as I am stumped? I am swinging towards a bad reed valve, but they do "appear" to be seated correctly, but because I can not find a good diagram of what they are suppose to look like, I can not be sure. I can take the outlet tube off of the head and I get no air release from the tank.

On a side note, There is a secondary but smaller port next to the outlet tube on the head that is capped. Anyone know what this port is used for or can be used for?
 

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I'm wondering if there is a run capacitor in the motor that has gone bad and now the motor no longer can spin the pump after a certain pressure
 

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Discussion Starter · #3 ·
I guess I never thought of that. Its going to be another week before I can even get back to it to check. I will let ya know.
 
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