What is an engine stop solenoid?

An engine stop solenoid is an electromagnetic device designed to cut the fuel supply to an engine to force it to stop. Most mechanical engines have stop solenoids fitted.

How does a engine stop solenoid work?

An engines stop solenoids normal state is not energized (i.e. there is no power to it). In this state most solenoids are in the closed position, so the fuel cannot get past. Before the engine starts, the solenoid is energized, which opens the flow of fuel to the engine. The engine then cranks and should start. When you stop the engine, the power to the stop solenoid is removed, which closes the fuel line and the engine then stops.

This means if power to the solenoid is lost while the engine is running, the fuel supply will be cut and the engine will shutdown.

Where can you find the engine stop solenoid?

The stop solenoid is usually located at the entrance to the fuel injection pump or in the fuel line before the fuel injection pump.

At a state of rest, the solenoid will have no power and need to be energised to allow the engine to run. In the case of a generator, the solenoid is usually controlled by the generator control panel. When you press the start button or turn a key, power is sent to the solenoid to allow it to open, before the engine is cranked. If the solenoid is not open, the engine won't start, because it will not have any fuel supply.