Hi. I have a Delta/Porter Cable 80 gallon compressor and when I try to switch it on the motor turns very slowly at first then turns a little faster then slows down again. It does this all in maybe 1 revolution. It's like it is struggling to make one turn.

Is there a pressure relief valve that may be malfuntioning or is the motor possibly the culpret??? Also, it is trying to turn for about 3 seconds and then trips the breaker.

Does anyone know what could be the problem or what I can do to try and diagnose whats wrong. Anyone know of a compressor forums/group anywhere? I have searched the net but not come up with a group dealing with air compressor issues (hard to believe since there is a forum for just about anything now).??

Thanks,
Rodney

 

did this just start happening or has it always done it

 

It just started recently.

 

empty tank, or kick on pressure in tank??
if it is with an empty tank, either the motor is bad, or the compressor is bad.

if it is with kick on pressure in the tank(like 80lbs) the head pressure popoff valve is probably bad

 

Well, it started with full tank (120 psi) and now it's down to 50 psi and doing the same thing.

 

Depending on motor type/size, voltage, etc, could be centrifugal switch, starting cap, motor starter, heater, low line voltage, etc. Need to do some investigating to narrow it down. First check would be line voltage and current draw at the motor. And if you don't know how to do this, get help. (Just a cautionary note),

 

loosen the bled line that goes to the pressure control(the small 1/4" line that goes to the bled off valve), you can determine if the bled off is not working and/or the tank check is bad.

 

Ok, I just tried to trun the pump by hand and it was a little hard at certain parts of the revolution. I disconnected to belt to the motor and turned it on and the motor turned without any problems. I then went to the pump and hand turned it and it is hard to turn then it gets easy then hard to turn again.

I do have 220v at the compressor and it is about a 25ft. electrical run from my breaker box with 10guage wire. I'm also using a 30 amp breaker. I have not tried disconnecting the pressure control line. When I do disconnect the line do I just run the compressor and if so if it still does the same thing what does that mean? Bad motor?

Thanks.

 

If the motor has more then one capacitor, one of them is most likely failing. The problem sounds exactly like something at my father's work. They have alot of large heat/ventilator units, with 3-4' diamter fans, with dual capacitor 1.5HP motors. Good working motors will get the fan spun up in under 2 seconds, while one that got submerged during a flood, takes a good 30 seconds to get upto speed, once its up to speed it runs fine and has plenty of power, but one of the capcitors probably got killed during the flood, killing starting torque.

Let the motor sit for a while to make sure the capacitors are discharged, and then check the capacitance of each capacitor DISCONNECTED from the motor, and compare your readings to the specified level usually printed on the side of the cap.


The harder easier thing you speak of is normal intake-compression strokes of piston compressors

 

First, drain the tank and give it a try. If it does the same thing, then the compressor is most likely bad.
When was the last time you changed the oil and air filter?

 

i agree. drain the tank and try it.
if it runs with no problem, then you have a bad/stuck head pressure bleed off valve.

 

Thanks for the responses. I will try the sugestions above and see what happens. Hopefully I can figure out what is the problem...motor or something in the pump. I don't want to go out and buy a motor if it is something with the pump. Thanks again for all the help. I'll post this evening after I try it.

 

The filter is clean, I checked that the other day. The oil has been a while and is due for a change. I was about to buy oil to change it when this happened first.

 

If you can turn the pump itself by hand, it is most likely still good. Do you have anything else that is belt driven that you could test the motor on?

 

this is why i think the head pressure blow off valve is bad
he said the motor spins fine with the belt off, and the compressor head binds up when turned by hand. if the blow off valve is bad/sticking closed, every time the compressor tries to release the compressed air after the exhaust valve opens, it is going to get compress air already in the head pipe trying to backfeed into the compressor head.