CM2350 Air Compressor unloaded valve?

[Jose9640]

I have a cm2350 with air compressor issue? Shut off truck, build air pressure to 120psi. Then after that it will not rebuild pressure. Decrease air pressure to 60psi and it will not rebuild pressure. Just stays stuck there. I shut off truck turn back on and rebuilds 120? I’m thinking the unloaded valve is bad or could it be something with the air dryer?

[Lonestar10]

air dryer or governor shuttle valve getting stuck. i have do my air dryer every 6mo just to prevent any issues and its a relatively cheap insurance item to do on air system.

[Nilao]

My dryer is factory original. 980k miles and only gets a desiccant filter every 6 months. Put a new governor on it last year because it was only pumping to 115psi and cut in at 95psi.

I had a freinds unloader valve stick and that kept it from building air similar to your issue...had him unhook the outlet and inlet pipe and run marvel mystery oil through it an ounce at a time. It puked all kinds of nasty soot out and freed up the valve to get him home where he had the compressor replaced. You could do the same thing to see if its the unloader valve in the head sticking but once the start to go the need to be replaced asap. The governor is a $20 item at most stealerships and about 30 minutes to change out.