Replace pump or entire air compressor?

[mustangtyson]

We bought this compressor new and it broke a few years back. It will not start. It tries to but cannot get the initial inertia to spin the pump. The electric motor works fine when disconnected. The pump makes banging sounds like rod knock when turned. I believe this added friction is too much for the electric motor to start. The aluminum pump i believe is a bad design and should not have failed with our limited hobby use.

Is it easy to replace this pump with a better quality cast iron pump and save the rest of the compressor or should a entire new unit be purchased? What pump do you recommend as a replacement? How do you determine if a pump will work as a replacement?

Details on unit:

Compressor: Coleman (Sanborn)
Model: cl6506016
Hp: 6.5 (on tank)
Tank: 60gal.
Motor: magnetek ac century
Horse power: spl (on motor)
Volts: 208/230
Amps: 15
Rpm: 3450
Time: cont
Hz: 60

 

[scw1991]

I'd open up the compressor to see what the knocking sound is all about. Could be something as simple as a bad rod/bearing.

http://www.mastertoolrepair.com/sta...essor-parts-cl6506016-cl7006016-p-749116.html

Most of the time, if the motor cannot start up it's due to a bad motor start capacitor or the unloader valve at the pressure switch is not functioning properly.

 

[57JoeFoMoPar]

That aluminum pump isn't the stoutest of designs. I know HF's rep on here, and how much of it is well deserved, but their compressor pumps get pretty good reviews and have decent performance. If you're not needing a 100% duty cycle pump, grabbing a new head from HF may be a more cost effective and better long term solution, especially since their pumps are at least cast iron.

 

[PT Doc]

6.5 hp.

More like 3 and change.

 

[Shop Dad]

6.5 hp.

More like 3 and change.

Yeah, that drives me crazy...

A new HF pump may be your best option. The tank is still good but thinner than better quality compressors, so it doesn't make sense to sink a lot of money into it.

 

[ernie2525]

Bad capacitor.

 

[Davefr]

Bad capacitor.

How can a bad cap cause rod knock?

 

[MacMcMacmac]

I wouldn't give up on that pump yet. They are simple, and easy to fix. If the oil level wasn't neglected, it may be something as simple as a loose rod cap. I agree it sounds like a bad capacitor with regards to the hard starting, or a stuck centrifugal switch inside the motor.

 

[redmondjp]

I wouldn't give up on that pump yet. They are simple, and easy to fix. If the oil level wasn't neglected, it may be something as simple as a loose rod cap. I agree it sounds like a bad capacitor with regards to the hard starting, or a stuck centrifugal switch inside the motor.

Yes, at this point there is nothing lost but an hour to further investigate it.

If the pump does turn out to be bad, I'd go with the Harbor Freight one as already recommended. But do your homework on it and search for other threads on here, as your motor is essentially a 3HP (continuous) one.

If you buy the Harbor Freight compressor that says 5HP, you're going to have to slow down the pump speed in order to run it with your 3HP motor. Otherwise, the motor will be the next thing you are replacing on it!