This can basically be caused by 3 things:
1) There’s a sensor error, which shuts down the machine as soon as you let go of the starter switch.
The alarms are overruled during starting, so any broken sensor will give off a permanent alarm that will stop the engine as soon as you let go of the switch.
The sensors on these kinds of machine are most of the time simple just switches. They are either ON or OFF. So, it’s easy to check them. Look for the:
– engine temperature sensor/switch
– engine oil pressure sensor/switch
– compressor element outlet temperature sensor/switch
It could also very well be an broken wire to/from one of these sensors, or somewhere else in the control system.
For stopping, the machine probably has a ‘fuel cut-off valve’. This small device cuts of the fuel supply when you want to stop the engine.
These cut-off device needs to be powered (12 or 24volts?) to be open (it’s a normally-closed valve). So if there’s a broken wire somewhere, the cut-off will close and the engine will shut down.
So check if this cut-off device gets any power, check all the sensor switches, and check for any broken wires or bad connections!
Good luck! Would love to hear if you manage to find the problem.