If the cable breaks or the servo fails, at what speed does the engine stay?
If the cable breaks, the link between the actuator and the throttle lever is cut and the lever goes to the position its own spring or return arrangement takes it to; this is usually the idle side, but the exact behaviour depends on the mechanics of the engine. The kit cannot stop the engine. For that reason shutdown must always be built with a fuel shut-off solenoid, on a separate circuit.
In case of a cable failure, clamp slippage or servo failure the outcome is not the same on every engine:
- If there is a return spring on the throttle lever that pulls it to idle, the lever returns to idle.
- If the lever is held only by friction it may stay in its current position; that is, the engine keeps running at that speed.
- If the lever is held in the opening direction by spring force, the speed may rise.
This uncertainty is exactly why safety must not lean on the throttle side. During installation do the following:
- Before fitting, try and see the natural position of the throttle lever with the cable removed.
- Connect the emergency stop button to the fuel shut-off solenoid; prefer the ETR type for fail-safe behaviour.
- Check the cable periodically; look at clamp tightness, sheath crushing and wire fraying.
No sensor detecting a cable failure and no emergency stop input are declared on the GS740 and GS740-3P; protection comes entirely from the engine's own shutdown circuit.
Full article: Electronic speed and throttle control on a diesel engine