What should be done against the risk of overspeed and diesel engine runaway?
Overspeed protection is a separate arrangement that typically trips 10-20% above rated speed and requires a manual reset. In a diesel runaway the engine uses hydrocarbons in the ambient air or crankcase oil as fuel; cutting the fuel is not enough, the only proven solution is an automatic air shut-off valve fitted to the intake manifold. The GS740 and GS740-3P do not include these protections.
Two different events need to be separated:
- Overspeed: the engine accelerates excessively through the normal fuel path. The protection measures the speed and cuts the fuel; the typical threshold is 10-20% above rated speed and it requires a manual reset after tripping.
- Runaway: the engine burns hydrocarbons in the intake air or oil originating from the turbo or the crankcase. Even with the fuel path completely closed, the speed keeps rising. The solution is an air shut-off valve that mechanically closes the intake.
The role of these kits is clearly limited: they drive the position of the throttle lever. The taught upper limit restricts only the actuator stroke; if the engine accelerates because of its own mechanical governor, the fuel system or the intake air, the kit neither detects nor prevents it. In risky environments (sites where gas may be present, old engines with turbo oil leaks) overspeed protection and an air shut-off valve must be installed separately.
Full topic: Electronic speed and throttle control on diesel engines