Hi,

Your inlet valve is stuck in the open position.

The inlet valve opens and closes according to your pressure set points.

Open = air sucked in = compressor running loaded
Closed = no air sucked in = compressor running unloaded

So in your case, it is stuck in open position.

When the maximum pressure is reached, it just continues pumping air, and the pressure will keep rising. Your safety valve will blow, or your compressor will bog down becuase of the increased load.

When you do stop the machine, the pressured air and oil find it's way out of the air compressor by flowing back through the inlet valve. This is the oil vomiting that you see.

Now you need to find the problem.

It could be that either the inlet valve is physically stuck. It may be dirty inside, the spring is broken, etc, etc.

Or there is a problem in the control system.

The electrical control system outputs an electrical signal to a solenoid valve.

That solenoid valve then opens and closes control air supply to the inlet valve.

It depends on the inlet valve type, but in most cases it will open when compressed air is applied and it closes back by spring force.

In other models, it's the other way around.

I would start checking for an electrical open/close signal at the solenoid valve. Also check that it opens/closes (you can hear it click) and that air really does come out of it (disconnect the hose).

Be careful when opening the inlet valve. The main body has a powerful spring inside. When opening, make sure to be careful and remove the tension of the spring carefully.

Good luck with finding the exact problem.

All the best,
Cas