Small (2 gallon) air compressor not filling tank

[Number_35]

My friend brought his small (2 gallon) air compressor over for me to try to repair.

It is oil-free, and runs off 120 VAC.

The electric motor seems to work well, but there's no output from the tube which comes off the cylinder head.

We opened it up, and I was unable to figure out how it's supposed to work.

I expected some sort of one-way inlet valve, but didn't find one. (There is a spring-loaded output valve in the head, to allow air to be pushed into the tank but not to flow back.)

Strangely, there's a hole in the piston which appears to be there from the factory. It seems as though the air would escape through the hole as it's being compressed. We considered installing a bolt to block it, but there's zero clearance between the top of the piston and the bottom of the head.

And even if it were blocked, it looks like the only source of intake air.

Has anyone else worked on one of these? I looked at some YouTube videos, but all showed logical intake valving, and none showed a hole in the piston.

The yellow Allen key is simply to show that the hole in the piston goes right through.

These is a recess in the head for the screw head on the piston.

 

[JohnnyG]

Never had one apart, but I'm thinking THOSE ARE THE VALVES in the piston (or are supposed to be.) That hole should be a valve.

 

[Number_35]

Never had one apart, but I'm thinking THOSE ARE THE VALVES in the piston (or are supposed to be.) That hole should be a valve.

So there should be some sort of one-way valve in that hole, right?

Turned the compressor over and shook it, but found no loose parts.

 

[Dave Sherman]

Could there have been a reed valve held by the screw that broke off? For that hole to be the inlet, the reed would have been on top of the piston. Is there a thin piece of metal under the screw?

 

[mk378]

Yes, there's supposed to be a reed valve on the piston so air can only flow in. I see damage to the top of the piston from having something loose inside the cylinder.

 

[Trav]

I doubt any internal parts are available for that one, they probably off the whole motor and pump assy. Bin the thing if that is the case.

 

[JohnnyG]

Or make the part yourself.

 

[wings&wheels]

That was also sold in red as a Coleman, if that makes your parts search easier. I have one from ~2003 that, luckily, has been one of my most reliable tools

 

[Dave9]

On different compressors some have had success making a reed valve out of a piece of ~0.005" feeler gauge.

 

[Number_35]

On different compressors some have had success making a reed valve out of a piece of ~0.005" feeler gauge.

That is a very good idea! I may try it - I have several ancient feeler gauges kicking around in my toolbox.

Could there have been a reed valve held by the screw that broke off? For that hole to be the inlet, the reed would have been on top of the piston. Is there a thin piece of metal under the screw?

I'll remove the screw and see if there's a remnant. That will help me determine the thickness as well.

 

[ironman_gq]

I've had one of these apart in the past, definitely a reed valve on top of the piston.I've made them from .005ish shim stock but I think a feeler gauge might be more flexible and last longer.

 

[Number_35]

I've had one of these apart in the past, definitely a reed valve on top of the piston.I've made them from .005ish shim stock but I think a feeler gauge might be more flexible and last longer.

On different compressors some have had success making a reed valve out of a piece of ~0.005" feeler gauge.

I cut down an old 0.004"/0.010 mm leaf from a set of feeler gauges.

The compressor works now, but takes a few minutes to reach 100 psi.

That could be due to the inefficiency of the new reed valve, or could be normal. In any case, I think my friend will be happy with it.

Thanks all who replied!