The ignition and detonation of low flash point lubricants due to the high temperature generated during the rapid compression of air in a spring-piston air gun.
If a petrol (gasoline) engine gets overheated it is possible that with no spark being produced the engine still continues to run. To stop the engine the fuel needs to be turned off.
This is similar to diesel engines that rely on the combustion of air and fuel when compressed. In this case the pressure is provided by the main pumps and the cause is excessive air in the fluid and/or too high a vacuum on the suction side that allows the formation of free air bubbles. Temperatures in the wall of the air bubble being compressed can reportedly reach hundreds of degrees so that some fluid degradation is likely. It can also be called adiabatic compression that is the worse case scenario with no heat transfer into the fluid.