Portable compressor XAS175 will not speed up

Hi, The Atlas Copco portable compressors regulate the capacity and pressure in two ways: by opening and closing the inlet valve (unloader valve) and by increasing/decreasing the engine speed. In your case, something is wrong with the speed regulation. When you use air, the pressure will drop, and the engine should increase speed. From the regulating valve (where you set the pressure), two pneumatic lines run, one to the inlet valve and one to the engine speed controller. The speed controller is a small piston that acts on the pressure from the regulating valve. It is connected to the speed controller of the engine by a rod/link. You will probably find the fault somewhere over there. The piston should pull the engine lever to the left, to increase speed. You can do it by hands, to see if that increases the speed. If it does, you know there is nothing wrong with the engine. I have included some pictures of a XAS175. This one has a Deutz engine, but yours should look about the same. 1st picture: regulating valve 2nd picture: piston that pulls on the speed lever of the engine to increase speed 3rd picture: speed lever/setting of engine. 4th picture: diagram of speed control of the engine. Good luck. Let me know if you need more info. I'd also love to know the solution when you fixed it.