Kobalt 1.6HP compressor will not run

by Mo
(Lewisville, NC)

Compressor was dropped before it was ever turned on an one of the cylinder heads broke off.

I have a Kobalt 1.6HP 30 gallon compressor with a twin head pump.

I ordered a new cylinder, gaskets, and rings.

After replacing the cylinder, gaskets, and rings the compressor would not start. The motor hummed but didn't seem to have enough umph to turn the pump.

I followed many of the suggestions on this sight including checking the start and run capacitors.

I then plugged the compressor into a dedicated 20 amp 120 circuit with the same result.

I then removed the drive belt. The motor starts without any issues when under no load.

I know very little about compressors.

I tried hand turning the pump pulley by hand. It is very hard to turn.

I removed both heads and it still was hard to turn.

I removed the cylinder I had just replaced and it seemed to turn reasonably well which seemed to remove my doubts about other internal damage.

I put the head back cylinder the opposite cylinder.

With one cylinder in tack and the one where the cylinder was broken removed the pump could be hand turned without much effort.

I reinstalled the new cylinder and I could still turn the pump by hand but it was a little stiffer but not as stiff as when fully assembled.

I reinstalled the head and connected the lines. At this point I could still turn the pump but it was much harder.

Seemed a bit easier than when I first tried but still much stiffer to turn than when the head was off.

I tried powering back up but not much different than the first time I tried to power it up.

Not sure where to go next. Suggestions are greatly appreciated.

Thanks in advance.

I must admit I know a lot more about air compressors now that I spend considerable time on your site.
Thanks Mo. Glad the site has been informative.

The humming motor means that it is trying to start, but cannot.

Can the pistons be cycled more easily with the line from the pump head to the tank removed? I suspect not, but that's a good way to ensure that the tank check valve isn't the problem. With the line off, if the pistons cycle easily, that would suggest a blocked tank check valve.

Since you have already checked the other things that might cause the motor to hum, and they are good, then the only other thing that remains is that something about the reassembly and working of the new cylinder is backloading the motor to the point where it cannot start against the load.

Sorry Mo. Wish I could be more help.


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Oct 14, 2013
problem solved!
by: Mo

After trying several things to isolate the issue I discovered the replacement cylinder I installed was not square to the compressor shaft.

I removed both cylinders so there was nothing but the connecting rods and pistons. I could hand turn with ease.

I installed the original cylinder without the head on the non-broken cylinder and was able to hand turn with ease.

Then I installed the new cylinder which replaced the broken one for the 2nd cylinder and it was hard to turn. Hmm. I had already honed the new cylinder several times so I felt it should work. But still having problems. I then loosened that cylinders bolts and could turn the compressor. Tightened back - couldn't turn. Hmm.

I then aligned the top of the cylinder to the new head and tightened one of the bolts. I could still turn but when I tightened the opposite nut it became stiff again.

I found the right combination of tightening the nuts which kept the piston head aligned to the top of the cylinder and it was still easy to turn.

I removed the cylinder and used a shim between the cylinder and body along with "The Right Stuff" to form a new gasket. Then reassembled the rest of the compressor checking at each step to make sure I could still turn the compressor easily by hand. IT WORKS!

If I had all the fancy measuring gadgets that might be found in a machine shop I probably could have figured this out earlier.

This site helped immensely in eliminating many other possibilities but this one almost stumped me.

Now on the the next project.
Good on you Mo. A great read, and my congrats on digging down through the issues to figure out what was what.


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Kobalt 5-HP 80-Gallon 155-PSI Electric Air Compressor

by Aaron Miller

Do I need a 30 or 50 amp breaker for this compressor
According to what I've read, your motor will pull around 22 amps when running, but typically, the inrush on start up may boost that up past 30 amps.

So, it were my compressor, I'd go with at least a 40 amp breaker.

Anyone else? Maybe even someone that knows something about electricity? :-)


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Kobalt 17 gal. air compressor, Model No. 236005

by Darrell rau
(Columbus, Tx. 78934)

Will not start, engine is dead.
Not much info to to on here, Darrell.

Visit the troubleshooting section on the sitemap page and follow the link to the page about why air compressors don't start.

Do the checks and add a comment here with what you found, or didn't find.


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What is torque for head bolts on 232177 model?

by Jerry Slauter
(LaPrte, Indiana)

Just put in new piston and connecting rod. Compressor builds 80 PSI and will bono further. No signs of leaks, but pressure is obviously lst somewhere.
Jerry, there is a general guide under troubleshooting on the site map page.

Your compressor symptoms however don't point to leaking head bolts but rather a valve or gasket problem.

If you did not use a new gasket kit, or if any of the valves were dirty, damaged or installed incorrectly, that could lead to the running but not building past 80 PSI.

My first thought is that your pump has a gasket leak between compress and high pressure side that is opening at around 80 PSI.


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