# Engine stops at 80psi



## pawned (Apr 1, 2017)

I had a 5hp B&S engine at the house. So I decided that it would be great to power an air compressor.
I found a 80-90+ air tank and then added the 5hp air compressor from Harbor Freight. As shown in the picture. I have since added the unloader/check valve to the setup. With the trottle control cable. 
The unloader/check valve came with no instructions of any kind and as I have never worked with this before so I can only hope it is set up correctly. But it does not have that much to do except screw it in (that I know of)

When the psi in the tank reaches 80 psi, the gas motor shuts off.
It does not roll to a stop. It stops on a dime.

The engine is a 5hp Briggs and Stratton. It runs very well normally or when uncoupled from the compressor.

I imagine you all know more than me. Any ideas would be appreciated
For some reason the photo will not upload


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## motormonkey (Jul 10, 2016)

When preset pressure is reached on a gasoline engine type pressure switch, two things should happen. First, the pressure switch should activate the unloader/checkvalve, which releases the head of pressure the compressor is working against. Second, the pressure switch should reduce the engine to idle.

If the engine is reduced to idle before its load has been removed, it will stall as you describe. Sounds like the unloader/checkvalve is either not releasing the pressure head on the compressor quickly enough, or not at all.

You should hear the hiss of air being released by the unloader/checkvalve when the pressure switch is tripped.


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## pawned (Apr 1, 2017)

The unloader/check valve is set for 95 - 125 psi. I am not getting near that before the engine stops. 

For no reason at all I changed the spark plug and oil this morning. Maybe the old plug was not producing a hot enough spark to get full power from the engine. It is a shot in the dark, but it needed it anyways.

To quote my 'daddy', ' Do something, even if it is wrong'


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## pawned (Apr 1, 2017)

I have gotten it up to appx 118 psi and then it idles down and shuts off. Not sure why as the throttle control is not moving yet


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