stalling air compressor..??

[pistonhonda]

I have a small, single stage, electric air compressor that stalls out when the psi is above 40, but the unloader valve bleeds off when the motor cuts out ( I can hear the hiss of air). when it tries to kick back on at 90 psi it boggs down until the breaker blows, but if i bleed down the tank to 40ish psi it kicks on every time? could this still be a bad unloader or dirty valve?

 

[Outlawmws]

I'm confused: if it stalls out @ 40 how goes it get "down" to 90 for coming back on?

 

[Conor]

If I read it correctly it won't start to fill air if the psi in the tank is over 40

But below 40 and once it's started and filling it will fill all the way to max psi

My craftsman 5 gal does something similar. Not sure of the fix

 

[pistonhonda]

when i first start it up it fill up just fine but after using it and it reaches the cut in pressure of 90 psi it will stall / bogg down.

 

[stonesfan68]

If there is a separate unloader valve then try cleaning it out, or replacing it. The unloader valve could also be part of the pressure switch assembly.

 

[j.c.whitney]

^What he said^

 

[RECox286]

Yes, there is a problem with the unloader. That means that the motor is

trying to start while the compressors' head to tank is still pressurized.

Do you hear a hiss of air when the compressor reaches top pressure and

the pressure switch shuts the motor off ? Look on the side of the pressure

switch for a valve connected by tubing to the compressor head. It will be a

1/4" tube, unlike the larger tube that goes from the head to the check valve

at the tank.

Uncle Bob

 

[Charles (in GA)]

Some small SINGLE CYLINDER compressors have a different kind of relief valve. In stead of a pressure switch operated valve, they have a special valve in the tank inlet from the pump. The valve has a light spring in it. When air is not being pushed down on the valve from the pump, the valve springs up, closing off the tank, and opens up ports to relieve the head pressure in the pipe from the pump. The next push of air from the pump drives this valve down, allowing air to enter the tank, and closing off the head pressure relief.

This is an in-efficient design in that every stroke of the pump it relieves the head pressure, and the pump has to expend much of the air from each stroke to re-fill the pipe down to the tank. Thus every cycle of the piston, you hear the valve relieving air. This is usually found only on single cylinder pumps.

These valves are very prone to sticking and will stick in the open to the tank position, leaving head pressure on the pump.

Charles

 

[Steevo]

Also, most of these small compressors have a start-up draw that is excessively high compared to the run amperage. If you are running a 120 volt compressor on a 15A circuit, it may be exceeding the capability of the wiring, unless it is very close to the breaker panel.
My little "Scout" 120v oilless compressor will only startup if plugged into receptacles within about 30' of the panel.

 

[pistonhonda]

I have a small, single stage, electric air compressor that stalls out when the psi is above 40, but the unloader valve bleeds off when the motor cuts out ( I can hear the hiss of air). when it tries to kick back on at 90 psi it boggs down until the breaker blows, but if i bleed down the tank to 40ish psi it kicks on every time? could this still be a bad unloader or dirty valve?

Also since it only kills the breaker when it is above 40 psi would this still be an electrical issue? When i bleed the tank down below 40psi it will kick on just fine(tried it 10 times in a row, worked fine everytime below 40psi). I would think if it was electrical it would kick the breaker no matter how much pressure is in the tank?

Also i did notice that air was coming out of the unloader valve when it is trying to start up (above 40 psi) but it does not leak when the motor is off. Does this valve blow air when the the motor is running to help the piston or should it just relieve pressure when it reaches max psi??

 

[Major Ramifications]

If the unloader is discharging when it goes to start up, your check valve is leaking. But if this were the case, it would continue to leak after the pump shut off, draining your tank.
Are you trying to start it immediately after shutting it off before the unloader can finish unlaoding?
Some of the smaller compressors use a very small hole drilled into the check valve as an unloader. It leaks even while the unit is filling, but it is a very small leak. It does take this type of unloader a longer time to unload than the other types.

 

[Cryptic1911]

The unloader valve is there to let the air pump spin with no compression for startup. The electric motor can't produce enough torque to start at 0 rpms with the pump trying to overcome 90psi of air. The unloader lets the air between the pump and tank dump so it has little pressure until it is up to proper rpm, then it kicks in and starts filling the tank. When yours is below 40 psi, the motor can overcome the pressure and work properly. When it's over 40 psi, the motor stalls since it cant turn the air pump