Diesel "Runaways" and other failures to stop

[KevinCoughlin]

I read a bit on one of the other threads about diesel engines running the wrong way, and using the oil as fuel (and not stopping until it destroyed itself). So I thought I would bring up the issue in general.

Gas (and LPG, and CNG, and Alchohol) engines have spark plugs. If the plug fires, the motor runs. Turn off the key and no more spark, the engine stops.

Diesel engines do NOT have spark plugs. When the air is compressed it gets hot - add a little fuel in one way or another, and it goes BOOM and the engine runs. But how does it stop running?

New engines are setup to cut the fuel when you turn off the key to stop the motor. No fuel, no more vroom.... Older engines have a "stop lever". On my Detroit 6-71T I had a T-handle on the dash - pull it and it went to the fuel system and manually shut down the fuel.

On a GMC bus I was working on, the fuel stop lever was so corroded it could not be pulled. Before trying to get it to start, I made sure I could get it to STOP.

One evening, on my Detroit equipped rig, I pulled the stop handle after backing into my parking place (10 pm in a nice suburban neighborhood, and my big rumbling motor really annoying the wife....) and gave the handle a pull.... and it came all the way out of the dash.

For about 10 minutes I crawled around the engine compartment trying to find where this cable went.... enough time to wake up the spouse, and get told off soundly (something about a very early class tomorrow). So I drove off again to the supermarket parking lot to figure it out. In the dark I never did find the attachment that had come loose, but did determine I could un-attach the 8 inch flexible pipe from the air cleaner into the turbocharger, and shut it off by putting my hand over the pipe (or sticking my arm inside - I was 4 FEET from the turbo intake). At idle, it wasn't bad. I'd hate to have to try that if the engine was running wide open.

So..... if you have a diesel, figure out what you would do if it would not shut off.... BEFORE it happens. Maybe know where the tools are, or have a phone book you can set over the throttle body intake, or a plunger that can plug things up.....

Just my two cents... or three (this was long).

[lapeer20m]

Excellent point you bring up about shutting off your engine in case the little handle were to not do it's job.....I've also heard of people using a CO2 fire extinguisher directed into the intake to shut down an engine. Carbon dioxide is very very cold but i don't think it would really be an issue. DON'T ATTEMPT TO DO THAT WITH YOUR TYPICAL ABC DRY CHEM EXTINGUISHER!!!

on a separate but related note:

Diesel trucks that have great potential to work in flamable/explosive enviroments ie: fire rescue trucks that may respond to a refinery, or paint factory come equipped with a flapper valve that can be closed over the intake to shut the engine off in the event flamable vapors enter the engine. This can not only make the motor not shut off when you want it too, but it can literally scream past redline until something lets loose (like a rod, or the crankshaft)

[lapeer20m]

Originally Posted by KevinCoughlin

I read a bit on one of the other threads about diesel engines running the wrong way, and using the oil as fuel (and not stopping until it destroyed itself). \.

I don't think most diesel engines can run backwards. Even the 2 stroke DD's have exhaust valves instead of reed valves i'm pretty sure. A 4 stroke motor would never run in reverse.

a 2 stroke week wacker gasoline motor will run backwards....harley davidson made soem golf carts with 2 stroke motors that ran backwards when you put the machine in reverse.

[jdd]

i have a highway tractor with a mechanical cat engine and i am sure on 2 or 3 occasions when i have hit the key quick to start it it didnt start clean kicked back and started backwards i dont think you have to worry so much about it running away but the oil pump was probably blowing bubles in the oil pan so you would want to catch it quick but i guess you would figure it out when you put in gear or let the clutch out!!!!!!