In a true runaway I highly doubt that the shutoff lever would stop it as that is only used to cut off the fuel supply coming from the injection pump. In a runaway the engine is using its own oil as fuel, and since there is no way to control the amount of oil it is sucking up, there is no way to control it. I have heard a runaway can be stopped by cutting off the air flow using a piece of 3/4 or 1 inch plywood over the air intake on the air filter housing, but I really would not want to be that close to a screaming diesel running at over 6000 RPM.

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2012 Mercedes ML350 Bluetec 102K (hers)
2005 Corvette 55K (fun car)
2002 VW Jetta TDI 238K (mine)
1998 Volvo S70 T5 Turbo 211K (kids)
1994 Ford F150 4WD 246K (firewood hauler)
1983 Mercedes 300D 384K (diesel commuter)