Air compressor problem

[LCHIEN]

OK, I need help - all you air compressor experts.

My 4 Gal pancake oilless compressor, Sears Craftsman "Professional" (black model), when I turn it on the motor just spins, sounds completely unloaded, when I unplug it, it coasts for a while to a stop. No air pressure, of course.

I haven't taken anything apart yet, the manual has a trouble shooting section but that symptom is not listed. I'm not real familiar with these devices.

What does it sound like? I would assume the induction motor is direct coupled to the compressor pump reciprocating cylinder. Is there a linkage that broke? A shear pin or something to prevent locking up the motor?

Or maybe the piston is actually pumping but with no load (air inlet blocked, check valve problem, what?)

Your help appreciated.

(maybe I should head on down to Rockler and get the $129 PC pancake compressor and brad nailer combo for $129...)

[Thom2]

Loring, as you very well know, troubleshooting something like this with a vague description is pretty near impossible. If it's the same pump unit that my craftsman 60g had, then it could be any number of things from a sticking intake/exhaust valve in the pump head, to blown rings (they were only nylon IIRC), to a blown unloader valve, to a shear pin on the motor connection.

As much as I'd like to help, I'm afraid you're just going to have to tear into it ... I'm an audio/visual type of guy, even hearing what it's doing over the phone would help a TREMENDOUS amount, but you're still going to find yourself tearing into it either way.

a few tips for trouble shooting,

1.) if you can, disconnect the exhaust line into the tank and put your finger over the fitting at the compressor head, you should feel some sort of pressure with the unit running

2.) if this is the oilless unit that I'm thinking of, rip the plastic shroud off, I think the bottom of the piston is exposed and you should be able to see if it's reciprocating or not

If you don't have pressure at the exhaust side of the head, but the piston is indeed reciprocating, then chance are pretty good it's either a stuck valve or blown rings.

HTH

[Tom Slick]

a friend of mine had the same problem. the exhaust valve had a bit of debris holding it open. easy fix.

[Uncle Hook]

Make sure the drain value at the bottom of the tank is closed. If the drainvalue is open the compressor will run but the air will just run out.

[LCHIEN]

OK, after taking the cover off and trying to run it the problem soon jumped out at me.
The unit is direct drive, there's an "eccentric bearing" which is a bar clamped to the motor shaft. There is a hole in the middle of the bar for the motor shaft and one end is slotted to the hole and a bolt spanning the slot to tighten the part to the motor shaft. A bearing on the the end of the part attaches to a crank arm that is connected to the piston.

The crank arm was not moving tho the motor was running. Upon close inspection the eccentric bearing had a crack in it that intersected the slot and rendered the clamping action ineffective. the motor shaft was just spinning in the hole.

The parts looks to be machined brass, not a casting, and the cross section that cracked is about 1/2" x 1/2" I'd have to say its unlikely that I stressed this and it was a latent defect, but its well out of warranty.

Sears parts: $16 plus $10 shipping.

[cgallery]

Sears parts: $16 plus $10 shipping.

I'm impressed that the part is actually available. R U going to fix it? The shipping is a killer in terms of percentage of total.

[Cheeky]

Is that one made by PC, Campbell H, Ingersoll maybe? I know there used to be a website to cross-reference manuf. of Craftsman tools....maybe you could save some dough on parts.

I'll try and find the reference.

see if this helps

http://www.owwm.com/Craftsman/Manufacturers.asp

[LCHIEN]

OK, now I need more advise.
The first pic shows the cracked part (Eccentric bearing).
The second pic shows the assembly.
I have to get the crank arm off the eccentric bearing.
Since it has no side play, it appears I have to take off the piston head/cylinder (the part at the top with the heat fins),
removing the high pressure fitting and the four bolts that hold it.

Is there a problem with doing this - what is the seal for the head? A gasket?
Is it easy to reassemble?

[Thom2]

Should just be a gasket for the head sealing, probably just a paper gasket. Take your time and be wery wery careful to not rip it.

Disassembly/Reassembly should be pretty straight-forward.

[Cheeky]

Is there a problem with doing this - what is the seal for the head? A gasket?
Is it easy to reassemble?

Is this illustrated on the Sears parts' site?

[TheRic]

If you ripe the gasket, or it's damaged, or you want to replace it for the heck of it. You could get a generic gasket sheet and cut it to fit. They use to sell them at auto parts stores. I'm sure they still make them. Take the old gasket, or whats left of it, and use it as a pattern. To save time you could forget some of the holes / slots /cuts since the same gasket is probably used for several items.

Um Loring, don't use your router with a pattern bit to cut it, use a very sharp knife.

[Thom2]

You could get a generic gasket sheet and cut it to fit. They use to sell them at auto parts stores. I'm sure they still make them.

They still come FREE on the front AND back of EVERY cereal box


you really wouldn't believe how many times I've made gaskets from tablet backs and cereal boxes

[TheRic]

They still come FREE on the front AND back of EVERY cereal box
you really wouldn't believe how many times I've made gaskets from tablet backs and cereal boxes

I thought about mentioning that, and file folders but didn't want to overwhelm him. Besides the back of his cereal boxes probably already have the games cut out so he can play the game before the box is empty.

[LCHIEN]

Is that one made by PC, Campbell H, Ingersoll maybe? I know there used to be a website to cross-reference manuf. of Craftsman tools....maybe you could save some dough on parts.

I'll try and find the reference.

see if this helps
http://www.owwm.com/Craftsman/Manufacturers.asp

919.163550

DeVilbiss made it.

Looks very like their 100E4D-1 down to the individual parts, but with some small differences.... Hmmm
But the part number is identical (AC-0140), but is $32.62 Plus shipping. vs. $15.55 + shipping for the same part at Sears.
Cheeky suggested the PC C5100 compressor was similar, sure enough it uses the same eccentric, but the online supplier for Porter Cable, Toolpartsdirect.com wants 46.42 for the part withthe exact same number AC-0140.
So Sears is a LOT cheaper than the parts dealers (like M&S) for DeVilbiss or toolpartsdirect for PC.
OTOH it wasn't time wasted, the Devilbiss parts diagram had all the torques specified for the bolts in the compressor area.

[LCHIEN]

Cheeky, here's the exploded diagrams from Sears:

http://www3.sears.com/imaging/ImageP...&titleID=00002&
http://www3.sears.com/imaging/ImageP...&titleID=00001&

Ric: I can't use my router? Really?

Thom: Got it. Thanks.

CG: its a heck of a lot cheaper than a new one.

Picture of broken part attached. It's steel, not brass, and
the cross section where it broke is like .575 x .512" - ought to be pretty strong!
( I suppose all that steel to the left side is supposed to be a counterbalance to the bearing and piston, to keep the vibration down - doesn't work all that well ).

Thanks to all. I hope they have the part in stock. It's a **** of a mess now spread all over my working area. [P.S. 4-7 business days to deliver]