Larry, I was just thinking about air getting into thru the EGR valve on a runaway engine. That would all be exhaust gasses and it doesn't seem that they would support combustion very well. P E H

Larry is right. The surest way to kill the runaway motor is to stop the flow of fuel to the engine. I'd cut or rip off the fuel supply hose. The fuel in the pump will still let the engine run a short while but it WILL stop before too long without a fuel source. The lift pump moves MUCH more volume than the engine can use, and there is a constant, large volume of fuel pumped back through the return lines. Cut the feed, and there shouldn't be a whole lot that can sucked out of the filter, and the IP should be shoving excess out the return. Disconnecting the metal injector lines would be the most positive shutoff though.

Blocking the intake airflow may, or may NOT (as in Larry's case), be effective. Regardless, an ounce of prevention is worth a pound of cure (in this case, several hundred pounds of new engine). All DIY MB mechanics should own a MityVac, and if you just TEST a newly-installed shutoff valve, you won't have this problem!

__________________
Dave M.
Boise, ID
1997 E420 - 155kmi (Bugeyes)
1994 E420 - 145kmi (Blondie)
1993 500E - 193kmi (Lollipop)
1992 400E - 189kmi (Stinky Dirty)
Check out my website photos, documents, and movies!

Larry
This must be the thread:
Destroyed the Engine in my Daughter's 300D

Gilly

Larry, I want you to know that I appreciated that right from the first.... It was both brave and KIND of you to share that experience. You did not have to share it... you don't have someone there in the hinterlands who would have ratted you out... I am sure you have saved several people their engines in the time since you posted it.
Greg

gsxr,

I guess that I'm still not being clear. I am NOT talking about disconnecting the fuel supply hose. There is still enough fuel in the pump to destroy the engine. I AM TALKING ABOUT LOOSENING THE HARD LINES AT EACH INJECTOR ONE BY ONE.
That is why I say to have a 17MM wrench in your hands when you start it after IP work.

Have a great day,

Larry
GSXR is just getting the posts confused. I am the one who recommended pulling the supply hose/prefilter hose off.
After reading the previously attached thread, i noticed someone mentioned several (at least) minutes of running left due to the fuel in the main filter, which is correct. So I guess to be more effective, it would be better to cut the plastic line between the main filter and injection pump (the one actually going into the fuel galley (or is it gallery), and that may bring it down to an acceptable time period. May stop it faster than loosening individual lines, it's one of tose things that would take an actual "test car" to prove.

But the important message of course is to not let it happen to begin with, as you state.
The only runaways I've had have been oil runaways on 606 oil changes, those are scary.

Gilly

Sorry - my post wasn't clear! I edited it, should make more sense now...

__________________
Dave M.
Boise, ID
1997 E420 - 155kmi (Bugeyes)
1994 E420 - 145kmi (Blondie)
1993 500E - 193kmi (Lollipop)
1992 400E - 189kmi (Stinky Dirty)
Check out my website photos, documents, and movies!

Even the fuel in the pump alone will take a while to use up, so I am told. I believe the best way is to have the 17MM in your hand when starting up after working on the IP. It will take only a half turn or so on each injector line to kill it. I think this would be quicker than burning up the fuel in the pump. Also, you are not ruining any parts. You will be able to fix your pump, tighten injector lines and restart.

Good luck,

The shut-off diaphragm - is this somethign that should be changed on a schedule. Perhaps checked often - but even changed out - to prevent possible breakage and ultimate run-away. As I understand it - the STOP lever in linked to "shut-off" IP. Why would'nt it be connected if shut off diaphragm leaks. OR are we talking about work having been done on IP (overhaul, etc) abd STOP being disconnected? If no work is done on IP - then STOP should generally always work? Is this correct? Thanks

No, the shutoff diaphragm does not have to be changed unless it is bad. The problem of engine runaway is not caused by the diaphragm faling. It is caused by the unit not properly installed. That's why you should check it with alternate vacuum source after removing and replacing it. If vacuum moves the stop lever, then the governor is "captured" and will not allow it to run away.

Good luck,