r/AirCompression • u/Either_Art410 • 4d ago
Compressor motor can't start unless the tank is mostly drained. Ideas?
I picked up this used Campbell Hausfeld compressor a few years back for cheap. I ended up having to replace the motor on it because it wouldn't start at all, even though the regulator was triggering it properly. (Although now I think I know why it burnt out).
I replaced the original motor with a similar 2 HP motor from Vevor. This motor works well when there isn't much air in the tank, but once the compressor cycles and the low pressure side of the regulator trips, the motor will not start. You can hear it buzzing trying to start and if you can push the pulley on the compressor itself, it starts spinning. But it can't seem to overcome that initial torque to spin. Is there anything I can do to allow the compressor to free spin before starting to compress, like a one way valve or something? Low tank pressure about 120 psi, high is about 150-160psi. I haven't touched the regulator.
3
u/CrustySailor1964 4d ago
There should be something that you can’t see that ‘continues’ down into the tank. There should also be some sort of provision for unloading the pressure when it stops.
It might even be some little cold start valve type of thing but hat is integral to the valve.
Worst case scenario, you can install a proper check valve with an unloader port and connect that to a pressure switch with an integral unloader.
All doable for under $100 easily.
3
u/SCAMMERASSASIN007 4d ago
When I read the problem it sounds like a start capacitor problem by the looks of the 2 humps you should have a start capacitor under one and a run capacitor under the other and since it runs fine when you help it start I would say the run capacitor is good but the start not so good. Although it is a new motor I wonder if a wire fell off or something crazy has happened. You need to read up how to test if you dont already and be awear if you touch both terminals it will feel like a hose kicked you.
2
u/mrcranz 4d ago
make sure the unloader valve is operating
1
u/jeffreagan 4d ago
I don't see provisions for one.
1
u/Gromitlikescheese 1d ago
Unloaders are used in gas powered compressors so the gas engine can get up to speed. Electric motors don’t use them because they develop max torque at stall. Agreed that it’s probably the check valve.
1
u/No-Wonder6102 1d ago
They do use them. quite often the check valve output has a head air bleed plumbed into the start switch.
2
u/Either_Art410 4d ago
I don't believe this has any kind of unloader valve.
3
u/New-Key4610 4d ago
the unloader valve is the brass fitting that is going into the tank unscrew. it and clean it with brake cleaner
2
u/Either_Art410 4d ago
To me that just looks like a stack of fittings. But I will unscrew that here in a bit and see what I find.
1
u/New-Key4610 4d ago
usually has a hole on the side to take the pressure off head they get gummed up and spray brake cleaner works well just a suggestion
1
u/No-Wonder6102 1d ago
there is your problem, no tank reverse flow valve as it seems to be using the one in the discharge of the pump head.
1
u/Most-Stranger-1 4d ago
That's a single stage pump, shouldn't be set to more then 110/115 psi max, that type of pump doesn't have an unloader. Check valve could be bad, and power cord looks small should be at least 10 wire
1
1
u/u3b3rg33k 4d ago
where's the connection between the pressure switch and the compressor discharge line?
1
u/Silver-Dress-4936 4d ago
When the unloaded is working there will be a woosh of air when the compressor stops.
1
1
u/Defiant_Shallot2671 4d ago
Those lumps on top are starting capacitors. The motor won't develop starting torque without them. I'd test/replace them.
1
u/ayrbindr 4d ago
Check valve, unloader, capacitor. I'm goin' with unloader here. Being that it looks as if it's a load genie. And the fittings seem mis align. Or, you are correct and it's just a bunch of fittings stacked on a check valve? God only knows. Maybe there ain't even a check valve on there? 🤷🏼♀️
1
1
1
u/Expensive-Youth-5709 1d ago
Quite a few comments are correct, there should be a check valve at the tank inlet, but a concern would be why you need 150 psi? Air tools are mostly rated for 90 psi. Small consumer compressors have a safety relief that is set at 150psi. I do not see a safety in the picture. A couple of other things to consider is to throw away the 16 or 14ga 25 foot extension cord get a 12ga. If running from a generator make sure it has the wattage for a loaded 2hp motor as the initial inrush can be as high as 50amps. Been on a lot of job site where the compressor is blamed and magically fixed with a heavier extension cord.
1
1
0
u/1994M-edition 4d ago
What voodoo magic is this!?! Why won’t it work?!? You have a bad tank check valve. Plain and simple. The motor can’t start against a load. That’s the pressure in the tank. Change that and I bet it fixes the problem
15
u/LazloHollifeld 4d ago
Bad check valve leaking pressure back up to the head. It’s located in the tank threaded in where the discharge line from the pump comes in.