Experencing blowby on my Craftsman compressor.

I have a craftsman 5 hp compressor it pumps up to pressure but it is leaking air through the air intake filter.

Bill comments...

Thanks for writing in. I hope that when you sent in your question you put your email address in the "notifications" area, so that you will know when I respond. That's the only way you'll be notified as to when a response occurs, and that's the only reason there's a place to put your email address in, at all.

You say you are experiencing "blow by" and that you have air exiting the intake filter.

If you think about what your compressor is doing... it draws air into a cylinder, and then alternatively pushes that air into the air tank.

To allow air into the cylinder there will be an intake valve (often just a flapper or reed valve) which pulls open on the piston backstroke, and then is forced closed by the air pressure when the piston is in it's compression stroke.

The air, as it gets compressed by the piston moving and reducing the available volume will either move into another cylinder (two stage compressor) or into the tank through a check valve, thereby elevating the air pressure in your tank.

In your case you have evidence that the air is being forced out the intake valve when the piston is in compression stroke.

That tells me that the intake valve is the problem, and that it's not closing tightly when the piston starts to compress the air.

If it's within your skills, clean that valve and then check for leaks. If that doesn't stop it, replace that valve.

If doing this is not within your skill set, take your compressor to a repair depot. Some repair depots are listed here. Explain the problem and they should be able to fix you up pretty quickly.



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Air seems to not be getting to the regulator.... but!

by Eric
(Skaneateles, NY)

Craftsman compressor.
Main pressure gauge looks normal and compressor makes good tank pressure up to 125 psi just as it should.
No air comes through the regulator. I opened up the regulator and I don't see anything that looks like it would block air flow. But as I turn the knob to the right it should let the air flow and I get nothing. Even when I completely bottom out the knob there is no flow.
I was going to replace the regulator but then thought the problem may be further up stream.

Bill says...

Hey Eric. We spent a wonderful afternoon in Skaneateles last summer. You have a wonderful town, and I recommend all to visit if they have the chance.

For those that are wondering how to pronounce the name, as we did, this is how it was explained to us by a welcoming local lady:

Skan - eeee - AT - Lass

Run 'em together, she said. Hope this is right, Eric?

As to your compressor issue, normally there is nothing in the air stream between the tank and the regulator. If the tank gauge is showing a full charge, then I'm pretty sure that the full pressure is getting to your regulator.

Regulators can be a valve too. If the regulator has been shut off, air cannot flow downstream. This could be the case if the gauge on the regulator is showing zero, since the gauge depicts the downstream pressure setting. Does your regulator gauge say zero?

If it does, and turning the knob does nothing, try pushing (up or down) on the knob to see if it moves in either direction. It is possible that the knob had become disconnected from the internal adjusting nut, and unless it is connect, you can turn to your heart's content and nothing will happen.

I know you say you turn it to stop, yet, I wonder what your regulator air gauge shows when you are turning the knob?



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model#919-165510 runs and won't build pressure

by Dave

I have compressor, model#919-165510. and it will only build to 20 lbs' but continues to run, and it does'nt leak... I"ve replaced the regulator but that didn't solve the problem... Please help..............

Bill says...

Dave, the problem of a compressor continuously running and not building pressure is a fairly common one, it seems.

I suspect that when your compressor reaches it's current maximum pressure of 20 PSI then it develops an intake valve issue, which intake air blowing back out the intake port through a leaky valve. That is one option.

The other is that the internal gasket between the intake port and the into-tank side opens at that 20 PSI, and the air cycles back and forth instead of going into the tank.



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