Air compressor - reed valve replacement

[stickshift]

I ran it up to 80psi, cracked open the pressure switch end of the unloader line - no air. Then ran compressor with my finger on the open end of the unloader line. Some air, but very little, not nearly enough to push my finger off. Then removed unloader line and ran compressor - lots of air pulsing out of check valve's unloader port. I used the air gun to blow out the unloader line - didn't see anything fly out, but I think you were right about there being something in there, because unloader line is certainly clear now.

Reinstalled unloader line and ran compressor - now I can hear air hissing while pump is running. Air is blowing out of the little port on the unloader valve. So there's no pressure in the head or discharge tube because it's getting blown out while the pump is running. This stops when the compressor reaches max psi and shuts off.

So that's one issue. Possibly bad unloader valve or pressure switch itself? There isn't enough room to see if the pressure switch is making contact with unloader when switch if flipped off.

Another issue is I'm now hearing a leak near the pressure switch area after compressor shuts off. It's a very slow leak. I timed the psi drop from 96 to 88psi. That 8 psi drop took ~12 min. I tested all the joints in the area with soapy water, but no obvious culprit. Couldn't feel any air flow around any of the joints. Might have to revisit that with better lighting. So I'm not sure if this is from one of the joints given that I was messing around in that area, or if it's a leak from within the pressure switch. Possibly the check valve? I guess I can test for that by removing the pressure switch end of the unloader line and feeling for air (and seeing if that stops the hissing).

 

[stickshift]

These older compressors can become quite the money pit. I rebuilt a trash pick compressor and between flex copper tube, fittings, paint, etc. well around 1- 2 hundred dollars....I had a reed valve that was cracked on mine.i wrapped it with HVAC duct tape. The silver foil type.

Yeah, I'm feeling that!

Given that compressor can get to max psi with both leaks (one during operation and one after compressor shuts off) as described above, I can use it as is. The very slow leak isn't a huge deal because it's a portable compressor for DIY use, so I'm only charging tank when I have a need for air, and I drain tank when I'm done. The leaking during charging means the motor and pump are working harder than they need to, but again, it's DIY use, so I'm not running it hard.

The hissing is annoying though.

 

[The Cobbler]

sounds like maybe there's something stuck in the unloader valve, holding it part way open and not allowing it to seat .
for your slow leak, the check valve could be the culprit, allowing air to escape thru the unloader valve . just have to keep looking till you find the leak. it should be easy to find as it's a fairly large leak

 

[Jswain]

If it's leaking from the unloader valve while the compressor is off then it will be your check valve leaking. Given it sucked up that air filter and it was fairly dirty inside the head anyways I would remove the whole assembly(individually so you get access to all the connections), pressure switch, safety valve, unloader valve, ******, check valve and give everything a thorough cleaning.

Reassemble with fresh Teflon tape and then check everything for functionality & leaks. Make sure you manually function the safety valve after cleaning to ensure air will flow through.

Some wd40 to get everything working smoothly followed up with some brake clean or similar will work

 

[stickshift]

Good news and bad news.

Good news is the leak during charging was the unloader valve. It was stuck open, which explains why, after I blew out the unloader line (and cleared whatever was in there), I could hear hissing while the compressor was running and why that hissing went away after compressor shut off (no more pressure in head and discharge tube). I cleaned up the internals of the valve, reassembled and tested function by connecting to unloader line - with compressor running, the pin pops up right away (see pic). Easy to press the pin down and air is released. Feeling pretty good about myself. And then the air pressure launched the unloader valve internals out of the unloader's brass housing and into orbit (into some bushes, but may as well have been orbit because those bits are lost forever).

Given that this style of unloader costs $20+shipping, I may be better off getting a cheap new 4-port pressure switch w/ unloader (and then I'd also have a cover; current switch is missing cover).

Check valve is good - there's no leak from the unloader line once the compressor shuts off.

I also found the slow leak (with compressor off) - it's the regulator. When I dial regulator pressure down to zero, hissing stops. Dial pressure up and hissing returns. So I'll remove the regulator and see if I can figure out what the issue is.

 

[The Cobbler]

it's a learning experience LOL been there, done that . probably makes sense to replace the pressure switch
The regulator has a piston probably made of plastic. it has probably cracked, and/or a bad oring . I have in the past been lucky to replace the guts with another one & not have to take the old one off .

 

[redmondjp]

Amazon has the Square-D pressure switches for very reasonable prices. There are dozens of different options as to port sizes, pressure on/off ranges, and so on.

I would not buy one of the Lefoo Chinesium ones just to save $10-15 however. YMMV

 

[stickshift]

Following up, I replaced the switch (lost parts of the unloader valve on the old switch). New switch works fine and now I can hear the distinct sound of the unloader valve opening when the motor shuts off.

I used this calculator which @Jswain linked earlier:
https://www.airgastech.com/resources/calculators.html#cfm-calculator

Use atmospheric pressure (14.7 psi) as starting pressure, 120psi final pressure and time of 2:24 to fill 20 gal tank, I get 8.0 CFM. Seems kinda high, for this style of compressor, no?

 

[The Cobbler]

I've never calculated the cfm on mine, but it's impressive for a small unit IMO

 

[Jswain]

Does it say on the sticker it's 20gallon? Perhaps it is a 10 gallon but it's hard to judge in the pictures

If so and the pressure gauge is reading correctly then I'd definitely be happy with that as long as the pulley on the motor wasn't replaced and spinning the pump too fast

 

[stickshift]

Does it say on the sticker it's 20gallon? Perhaps it is a 10 gallon but it's hard to judge in the pictures

Yes, sticker with model # lists as 20-gal.

On same sticker:
Displacement: 10.4 CFM
8.4 SCFM @ 40 PSI
6.7 SCFM @ 90 PSI

On a perhaps related note, I tried running it once on a 15A circuit (that did have other loads, but nothing large I don't think) and the motor stopped in 1-2 seconds. All other times, I run it on a 20A circuit that has no other loads. My prior Husky 10-gal compressor ran happily on that 15A circuit.

 

[Jswain]

Nice well then I would be happy with 8cfm and pat yourself on the back for a job well done.

The motor itself may draw 15amps and the startup draw is tripping the breaker it wouldn't be uncommon to require a 20amp circuit for it. It should specify the FLA on the motor sticker

 

[stickshift]

Nice well then I would be happy with 8cfm

Definitely happy with it. Just surprised and somewhat suspicious.

But assuming the 8cfm is legit, what does that mean for real world use? Can I use a mini die grinder - not for big jobs, but small ones such as removing old gasket material? What about an air hammer - again, not big jobs, but small jobs such as knocking a rusty ball joint loose, pushing out a stuck pin, etc.?

 

[gungatim]

I think they were devilbiss pumps. and I've heard of guys making new reed valves with feeler gauges .
you have the head off,
you may need more force on that plate but you don't need to remove that to replace the reeds
yes, use 2 wrenches on the nut & fitting.

you can also cut your own reed valves from bulk material they sell. used to make larger ones cutting the material (was like Kevlar or plastic or something) when we hotrodded 2-stroke mopeds. Malossi reed valve paper if you google it. Treatland was a great site...

 

[Jswain]

8cfm would run those both very intermittently. The air hammer wouldn't have too much of a punch for too long unless you hooked up a larger tank. Would be fine for impact wrenching lug nuts but if you find something real tough the gun will lose its punch quick as well but likely not a problem of you're just using it occasionally

 

[stickshift]

8cfm would run those both very intermittently. The air hammer wouldn't have too much of a punch for too long unless you hooked up a larger tank. Would be fine for impact wrenching lug nuts but if you find something real tough the gun will lose its punch quick as well but likely not a problem of you're just using it occasionally

Thanks. I'll pick up the cheap HF air hammer and see how it goes before investing in any other air tools that are at the margin of what this compressor can run.

Appreciate your and everyone else's help in getting this compressor up and running. I definitely got a crash course in how air compressors work, and will be a lot more knowledgeable when I decide to upgrade in the used market.

 

[Jswain]

That's what it's all about!