Compressor not reaching cut out pressure and continuing to run

by Gord
(Calgary, Alberta, Canada)

I was in the hardware store the other day and saw a small 1.5hp King Canada (model 8449) air compressor for $20.00. I had a look at it and it had a sign saying it leaked oil and didn't cut out. I took the chance and bought it.

I brought it home, changed the oil in it, filling to the recommended level,and gave it a 15 minute break in, running the compressor with the drain valve opened.

After 15 minutes I closed the drain valve and the compressor quickly built pressure to about 100psi, where it stopped building and held steady as the compressor motor continued to run.

I shut the compressor off and released the air in the tank, I then checked and tightened all connections on the compressor and started it again, it built to about 100 psi again and then stopped building and held steady.

While the compressor was running I checked it over and found that the is a significant amount of air flow out from the oil breather cap as well as a small amount of oil spay. The airflow will easily blow out a bic lighter and can be felt on the fingers 8" to 10" from the breather cap.

Bill says...

Hi Gord...

From the sounds of it your intake valve is pooched.

The valves on low end air compressors aren't good quality, and may even be poorly installed.

When the piston pulls air in the intake valve is supposed to open and the valve to the tank is supposed to be shut.

When the piston compresses, the compressing air is supposed to open the valve to the tank, and blow shut and seal the intake valve so air doesn't flow back out.

In your case, it seems to be doing just that.

The oil mist may simply be typical, or it might signal a piston seal is going.

Cheers and good luck.


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Dec 24, 2010
by: Gord

So I dug out the parts manual for the compressor and took the cylinder head off and played with the intake valve (which didn't look right), my first attempt had air coming out of the intake, so I took it apart again and gave the head a 180 degree turn, and there ya have it, the compressor is building pressure, reaching it's cut out and seems to be working just fine. A perfectly good little compressor, brand new, and for $20 bucks and a little time and effort thanks to you Bill!!


Hey Gord, good on ya for taking it apart more than once. Glad to hear that your air compressor is back in action.



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