Some years ago in our marina a new motor cruiser was running his engine at the dock. Low and behold - RUNAWAY
. After lots of running around & shouting on the dock and no-one knowing what to do it suddenly stopped (after what seemed like a very long time). The result - lots of oil and engine block pieces strewn all over the engine room.
Fortunately, this is not a common occurence but it certainly can happen.
Has anyone here had this happen to them? And, how did you stop the engine? What did you learn from the experience?
Some research on this rather frightening experience:
From a Mercedes website:
General causes of a run away diesel:
If the turbo seal leaks on the intake side, it feeds unregulated fuel into the combustion chamber.
If the piston rings leak on the compression stroke, the crank case oil mist gets blown through the CCV (crank case vent) and into the intake, this feeds unregulated fuel into the combustion chamber, add a restricted or dirty air filter and you have a run away diesel.
An over full crankcase oil level can cause massive unregulated fuel into the combustion chamber leading to a run away diesel.
If the intake valve guides leak and the head oil drains are clogged with sludge, it feeds increasing amounts of unregulated fuel into the combustion chamber, which can cause or contribute to a run away.
If the piston rings leak on the intake stroke, it feeds unregulated fuel into the combustion chamber.
The larger the volume of unregulated fuel going into the combustion chamber, the greater the risk of a run away diesel.
Your best defense against a runaway is:
A clean intake system and air filter.
Regular oil changes.
Keeping a log of oil consumption.
Watching for excess smoke in the exhaust.
How can you stop a run away diesel?
There are three ways I know of to shut down a run away diesel:
Seal the air intake and starve it, this can be impossible if the duct work is on the intake.
Shove a 20 pound HALON or CO2 fire extinguisher in the intake and empty it.
Run for your life and come back when it has stopped naturally.
CAUTION: THE DECOMPRESSION LEVER MUST NOT BE USED TO STOP THE ENGINE EXCEPT IN EMERGENCY SITUATIONS SUCH AS RUNAWAY ENGINE OR THROTTLE DAMAGE, AS SERIOUS DAMAGE CAN BE DONE TO THE EXHAUST VALVES.
Shutting off the fuel supply will not necessarily stop the "runaway" as it could still run on the oil at extremely high temperature.
And, from a Yanmar website:
"Hydrocarbon vapors in the intake air will sustain a runaway even with the primary fuel source removed. A diesel engine will burn a very wide variety of fuel, especially when at operating temperature, fuel is fuel, if it burns the engine will run, crank case oil will burn as fuel."
PLEASE share any knowledge of this possible problem.