Little compressor for $15

[freebo86]

Found a little Craftsman, 7gallon compressor, oiled on the local classifieds for $15.

Figured I give it a shot and tinker with in the garage. The guy said that the unit turns on but is broken.

Once i saw it I noticed there was no quick coupling after the pressure regulator so I was like doh! No wonder it doesn't build pressure.

Got it home, screwed on a coupler and it started building pressure. However it gets to 60psi then stops, it's bleeding air by the unloader valve.

Any idea what might be going on here? Do I need a new regulator switch? Unloader valve?

I changed the oil (quite watery) and the drained the tank which looked fine. Might be a worthwhile compressor to have around for smaller tasks if I can get it running.

 

[plinker]

Could have a damaged unloader line, still should get over 60psi before shutting off though. It's possible the pressure switch is bad or the previous owner messed with it.

 

[freebo86]

Could have a damaged unloader line, still should get over 60psi before shutting off though. It's possible the pressure switch is bad or the previous owner messed with it.

I checked the line that goes in the unloader and removed it and made sure it was nice and snug and still the air seems to be bleeding under the unloader valve. Don't think its the lines itself.

Can the pressure switch bleed out air something? I was under the impression that unit is purely electrical?

 

[plinker]

On pressure switches, It's basically an air operated electrical switch, psi maxes out, cuts the power. Psi lowers, switch cuts back in. It threads onto a pipe ******, so it could leak from there if not tight, ete..

They are also adjustable in regards to the cut in/cut out pressure, so it's possible it may have been tampered with.

Thinking about it, I have seen an unloader valve stick open in a pressure switch (may have been a bad spring, dont remember off hand). Pressure switches are fairly inexpensive, make sure the specs match.

EDIT; Here are some for around 10$, for some reason they have water pressure switches listed in there as well.
https://www.surpluscenter.com/Air-Pneumatics/Air-Tanks/Air-Pressure-Switches/

 

[sherrillkelby]

I am far from an expert on compressors, but I've been reading about how they work. Unloader valves are commonly plumbed to a check valve through which air enters your tank. These can stick open and let the air out of the tank through the unloader. Good explanation here if you scroll down to "When Unloader Hissing Continues":

https://www.about-air-compressors.com/has-unloader-valve-issues.html

It's strange to me yours shuts off at 60 psi. The pressure switch has a diaphgram that pushes up on a plate, which breaks switch contacts, stopping the pump. Factory switches are usually pre-set.

 

[Tracs]

Found a little Craftsman, 7gallon compressor, oiled on the local classifieds for $15.

Figured I give it a shot and tinker with in the garage. The guy said that the unit turns on but is broken.

Once i saw it I noticed there was no quick coupling after the pressure regulator so I was like doh! No wonder it doesn't build pressure.

Got it home, screwed on a coupler and it started building pressure. However it gets to 60psi then stops, it's bleeding air by the unloader valve.

Any idea what might be going on here? Do I need a new regulator switch? Unloader valve?

I changed the oil (quite watery) and the drained the tank which looked fine. Might be a worthwhile compressor to have around for smaller tasks if I can get it running.

I have rebuilt a few of these small compressors. Most of the time the gasket between the head and cylinder is blown out in the middle. I just make my own from gasket paper.

 

[The Cobbler]

if I understand your post the compressor shuts off at 60 psi, that is a pressure switch issue. most can be adjusted, it may be crapped out too
the hissing at the unloader, does it bleed continuously and let all the pressure out of the tank? then the check valve at the tank is bad. the unloader should hiss at the end of the cycle to bleed off the head pressure then stop. the check valve is there to keep the pressure from bleeding out of the tank

 

[freebo86]

if I understand your post the compressor shuts off at 60 psi, that is a pressure switch issue. most can be adjusted, it may be crapped out too
the hissing at the unloader, does it bleed continuously and let all the pressure out of the tank? then the check valve at the tank is bad. the unloader should hiss at the end of the cycle to bleed off the head pressure then stop. the check valve is there to keep the pressure from bleeding out of the tank

The unloader hisses/bleeds air continuously until there is no pressure left in tank.

 

[bczygan]

Check the check valve.

Bill

 

[freebo86]

Got a new pressure switch Leefo from eBay, screwed everything on. Same thing, hisses/bleeds air at the unloader valve which is brand new and part of the pressure switch that I just ordered.

Pressure builds up to 60 and thats that.

I circled the area on the picture where the air is coming from.

 

[bubinga]

Like mentioned above, Check the Check Valve.............LOL
Should screw into the tank, with A heavy line screwed into the valve.
(Looks like an Old GM gas filter housing on a 4 barrel Carb, if you're old enough to Remember them.)
Mine was doing the same thing, but also wouldn't restart after it kicked off, and blead about 20 PSI of air out of it. It would try to kick on, but kick the main breaker.
(Note; The Hissing at my Un-loader was continuous as well!!)

The Tank pressure was having a "Fight" with the head pressure.
Unscrew the fitting off the Check Valve, then the check valve out of the compressor.
Mine was about. 7/8" IIRC, took a long breaker bar, and My Girl at the time sitting on the tank to break it loose.
or zap it with a socket and an Impact if you have another air supply.
With the Check Valve in hand, try blowing (with lung power) into the side where the line fitting screws into the valve.
air should pass.
I wouldn't **** on the same end, might get a foreign object in you mouth/throat.
Instead, turn the valve around, and Blow into the end that screws INTO THE TANK!
It Should NOT PASS AIR.
Mine was passing air both ways, and It was a simple matter to "Rebuild" the Check Valve. An internal cir clip from Ace, and an old spring I had out of a spring Kit, and cleaning up lightly,
And....."Bob was my Uncle"
Check that and go from there.
If you don't have any springs, Ace should sell just a single spring.
It wasn't a very heavy spring.
If you don't want to "monkey" with it, a check valve is about $10.00 on e bay.

 

[bubinga]

Please follow up, and let us know what you find.

 

[TRWham]

Check valve is stuck, bad or trashed up. It is letting all of the air bleed out through the unloader. Also, where are you reading the 60 psi? The switch may be seeing something higher, but the gage is seeing only 60 psi. Could it be reading pressure after the outlet regulator?

 

[bubinga]

Check valve is stuck, bad or trashed up. It is letting all of the air bleed out through the unloader. Also, where are you reading the 60 psi? The switch may be seeing something higher, but the gage is seeing only 60 psi. Could it be reading pressure after the outlet regulator?

Good point TRWham, and the regulator needs adjusted.

BTY Welcome to the group.
I've been here a while.
You sound like a nice fellow, We have lots of those here, and can always use more.

 

[TRWham]

...

BTY Welcome to the group.
I've been here a while.
You sound like a nice fellow, We have lots of those here, and can always use more.

Thank you!

 

[bubinga]

Thank you!

 

[Ole Slewfoot]

My little free dewalt needed a cord.
then it ran continuous, and only made 40 PSI.
So I threw it in a ocrner for a few years.
then I pulled the head and found a bad valve.
Changed that, it made 60 PSI
Found part of the valve in the check valve. They are pretty expensive on that model, so I cut it open, dressed valve and seat, and epoxied it back together.
Now it kicks ***, but does lose 10lb or so overnight.

 

[freebo86]

Like mentioned above, Check the Check Valve.............LOL
Should screw into the tank, with A heavy line screwed into the valve.
(Looks like an Old GM gas filter housing on a 4 barrel Carb, if you're old enough to Remember them.)
Mine was doing the same thing, but also wouldn't restart after it kicked off, and blead about 20 PSI of air out of it. It would try to kick on, but kick the main breaker.
(Note; The Hissing at my Un-loader was continuous as well!!)

The Tank pressure was having a "Fight" with the head pressure.
Unscrew the fitting off the Check Valve, then the check valve out of the compressor.
Mine was about. 7/8" IIRC, took a long breaker bar, and My Girl at the time sitting on the tank to break it loose.
or zap it with a socket and an Impact if you have another air supply.
With the Check Valve in hand, try blowing (with lung power) into the side where the line fitting screws into the valve.
air should pass.
I wouldn't **** on the same end, might get a foreign object in you mouth/throat.
Instead, turn the valve around, and Blow into the end that screws INTO THE TANK!
It Should NOT PASS AIR.
Mine was passing air both ways, and It was a simple matter to "Rebuild" the Check Valve. An internal cir clip from Ace, and an old spring I had out of a spring Kit, and cleaning up lightly,
And....."Bob was my Uncle"
Check that and go from there.
If you don't have any springs, Ace should sell just a single spring.
It wasn't a very heavy spring.
If you don't want to "monkey" with it, a check valve is about $10.00 on e bay.

So basically the check valve is on the other end of that line I have circled. Correct?

Please follow up, and let us know what you find.

Will do!

Check valve is stuck, bad or trashed up. It is letting all of the air bleed out through the unloader. Also, where are you reading the 60 psi? The switch may be seeing something higher, but the gage is seeing only 60 psi. Could it be reading pressure after the outlet regulator?

The 60psi is read on the gauge which is after the pressure switch. See the red knob in the picture where I circled? Well that there is the regulator basically and the gauge is right at. I can provide a picture tonight.

 

[bubinga]

My little free dewalt needed a cord.
then it ran continuous, and only made 40 PSI.
So I threw it in a ocrner for a few years.
then I pulled the head and found a bad valve.
Changed that, it made 60 PSI
Found part of the valve in the check valve. They are pretty expensive on that model, so I cut it open, dressed valve and seat, and epoxied it back together.
Now it kicks ***, but does lose 10lb or so overnight.

good Job.
10 lbs. overnight, that's not too bad though!

 

[bubinga]

So basically the check valve is on the other end of that line I have circled. Correct?

yes, I would say so.
that is the model of the compressor?

 

[freebo86]

yes, I would say so.
that is the model of the compressor?

This is the unit right here;

Here is a pdf of it; https://c.searspartsdirect.com/mmh/lis_pdf/OWNM/L0520344.pdf

 

[Zexx]

The check valve will be the tank fitting on the big pipe coming from the compressor head. It sometimes also had a T coming off it for the small line going to the unloader.

 

[freebo86]

The check valve will be the tank fitting on the big pipe coming from the compressor head. It sometimes also had a T coming off it for the small line going to the unloader.

Yup! Thank you. Just as I assumed, the one thats off that small line I circled, which in the compressor picture there is blocked by the handle you can't see it but its like a T.

Thanks for everyones help! I'll be sure to update

 

[bubinga]

Nice looking little unit.

 

[freebo86]

So this must be the check valve but how do you get this thing off? Am I supposed to undo the red but which almost looks like it’s fuses to the tank or does the check valve itself come just off - because I have nothing to grip onto it to make it loosen..



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[freebo86]

Well on the backside of the check valve I noticed there was a 19mm nut, I loosened that easily and saw a spring with like a little white cap in there. Besides some light grease/black stuff on the cap I cleaned that all up and put it all back together and still same thing.

Air is hissing down at the unloader. Gets to 60psi and then slowly builds after that never wait long enough to see how far it would go.

 

[Zexx]

Now that I am home and can see your pictures decently. I would recommend checking the unloader and fittings around it with some liquid soap and see where exactly it is leaking from.

 

[freebo86]

Now that I am home and can see your pictures decently. I would recommend checking the unloader and fittings around it with some liquid soap and see where exactly it is leaking from.

Its leaking from the the opening between numbers 2 and 3. I have tried a unloader from a working compressor and it does the same thing on this compressor lol. So it is not that part that's faulty.

 

[The Cobbler]

the only time a properly working unloader bleeds air is when the pressure switch is in the off position ( air presssure achieved) . it will only bleed air from the head & related plumbing up to the check valve (if the check valve is working)
check to see that the tab (item 1 in your picture) has a gap between it & pin #2 when the compressor is trying to build air pressure

 

[freebo86]

Yup there sure is a gap there.



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[Zexx]

Does the pin (#2) actuate freely? Check it isnt bent or binding

 

[freebo86]

Does the pin (#2) actuate freely? Check it isnt bent or binding

Yup works perfectly fine. And as mentioned, I tried another unloader from my other compressor that works 100% and it was doing this same exact issue..

Can someone tell me what is supposed to be in that check valve? Could that be missing some sort of piece? Because when I took the nut off it in the back of the check valve all that was in there was a spring and a small white little plastic cap thing. Looking at the check valve I could see how this cap would get pushed back once the compressor head starts to create pressure and push the air down the line and into the tank. But I do not see how this thing would prevent any air from coming from the tank back out thus pushing the air into the unloader valve where its leaking. So maybe something is missing from this check valve?!?

 

[Citation]

Do you happen to have access to a second compressor? If so put together a male to male air hose coupler. Then use the good compressor to fill this one. If the check valve is your problem it will start to leak when the tank pressure gets over 60. That will confirm the problem is the check valve (or not).

 

[freebo86]

Do you happen to have access to a second compressor? If so put together a male to male air hose coupler. Then use the good compressor to fill this one. If the check valve is your problem it will start to leak when the tank pressure gets over 60. That will confirm the problem is the check valve (or not).

I do have a second compressor. Could you please explain where I am supposed to connect this male to male coupler?

 

[sherrillkelby]

So this must be the check valve but how do you get this thing off? Am I supposed to undo the red but which almost looks like it’s fuses to the tank or does the check valve itself come just off - because I have nothing to grip onto it to make it loosen..



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https://www.jackssmallengines.com/jacks-parts-lookup/part/sanborn/e100898

Here's the same check valve according to the part number in the manual you linked. It looks like it has flats you can fit a wrench on right above where it threads into the tank if you still want to remove it.

 

[freebo86]

https://www.jackssmallengines.com/jacks-parts-lookup/part/sanborn/e100898

Here's the same check valve according to the part number in the manual you linked. It looks like it has flats you can fit a wrench on right above where it threads into the tank if you still want to remove it.

Yah not a chance, I tried to put a wrench on that and there is not even room where the wrench would go and then one of the 90degree take offs. Unless you had a wrench that was like 2mm thick.

What I removed is that nut on the left had side and thats where my spring and white plastic cap is.

 

[Citation]

I do have a second compressor. Could you please explain where I am supposed to connect this male to male coupler?

I have made these things by getting two male air connectors, one with make and one female threaded ends (see center and right in this picture)
https://images.curbly.com/7CVhGodQc...om/photos/0000/0006/9856/aircompressor15a.jpg

screw them together with some Teflon tape. Now you can connect the two compressors via a hose. Note that this will vent if connected to a pressurized hose. Most regulators will also vent air from the line to drop pressure to the desired pressure. To deal with this I connect things in this order.

Connect hose to good compressor (don't have the adapter in the hose). Turn the regulator down.

Assuming the $15 compressor has no air pressure, connect the adapter and turn the regulator to full.

Connect the hose to the adapter and turn up the regulator. When it's time to disconnect you might have to just turn both regulators down at the same time.

 

[freebo86]

Thanks for the info but I still don’t understand. The male end goes into what the regulator end of the coupler that’s on the bad compressor? How can air be fed in this way?




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[freebo86]

Took the nut off the check valve my working compressor and no air leak! So it is the check valve spring and cap that’s busted in this unit.

Now the compressor still builds pressure slowly..


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[bubinga]

Could maybe put a big pipe wrench around the check valve?