Fuel Shut-Off Solenoid
The fuel shut-off solenoid is the element that actually stops the engine by electrically closing the fuel path or the rack of the injection pump. What stops the engine is not pulling the throttle lever to idle, but cutting the fuel. The emergency stop chain is built on this element.
The solenoid comes in two basic types: ETR, which permits running when energised, and ETS, which is energised in order to stop. Knowing which type you have is essential to building the emergency stop circuit correctly; a wrong assumption means the engine does not stop when a wire breaks.
- If the solenoid sticks or its supply terminal comes loose, the engine does not stop when the ignition is switched off; this is a safety fault.
- The solenoid coil is an inductive load; fitting a freewheeling diode at the contact terminal extends the life of the relay contact.
Rule: the GS740 and GS740-3P are not a stopping device. If the cable breaks, the actuator fails or the supply is cut, the throttle lever returns to idle by its own spring; the engine keeps running at idle. The stopping function must always be built through the engine's own fuel shut-off solenoid or mechanical stop lever.
Context in which this term is used: Electronic speed and throttle control on diesel engines