diesel guys--this is for you

blacksnapon · Jan 22, 2008

When referring to a diesel runaway, technician a says that you can shut off the motor by closing off air passages. Technician b says you can use a CO2 fire extinguisher in the intake to shut the motor off. Who's right? Tech a----Tech b-----both a and b-----neither tech

mrfixit · Jan 22, 2008

Halon gas, lol...

Technician A. I would reallllllly be leary of introducing CO2 via a fire extinguisher. That gas coming out is not just cold, but DANGED cold. I'd think you'd damage something.
If you close off the air intake, you take 1 of the 3 components for fire away. so "A" gets my vote.

6L PWR · Jan 22, 2008

I vote neither tech. Doesn't the fuel have some oxygen in it? Isn't that why it foams? Then I agree with Tom about the fire extinguisher. I think you gotta cut the fuel flow somehow.

Fellro · Jan 22, 2008

Back in tech school we used block off plates on the Detroits. Runaways don't always involve diesel, some will run on their own engine oil. Just be sure that your fingers are not under whatever you should place on an intake, that is if you like to keep your fingers attached...

Kep4 · Jan 23, 2008

Tech A is correct - cutting off air will shut a Diesel down. That's why Diesel sled pullers have an intake cutoff device. The throttle controls air intake hence engine speed.

Tech B - Not sure but since it's CO2, and that means two parts Oxygen, I would think that may make the situation worse! Unless it would freeze the intake air filter closed... not likely IMO.

6L PWR · Jan 23, 2008

Just curious, but that's not really possible on a 6.0 is it?

O'Rattlecan · Jan 23, 2008

out of the two things fuel needs to burn... removing air would stop ignition. Tech A...

Ryan

Kep4 · Jan 23, 2008

I must have lost my freakin' mind! :slap:

Both Tech A and Tech B are correct.

Skandocious · Jan 23, 2008

Hey Vince how 'bout the answer? You've got me curious now.

blacksnapon · Jan 23, 2008

Skandocious said:
Hey Vince how 'bout the answer? You've got me curious now.

both----- you need to shut off the air to shut down a runaway (turn key off, the engine keeps accellerating). I saw a guy try using a workshop manual to shut off a 318 detroit. It sucked it into the intake, shredding it, and keep going. Block off plates are good if you have the time. The fire extinguisher will work as well, but it makes a mess.

Bob Ayers · Jan 23, 2008

My Mercedes diesel has a fuel shutoff on the injector pump, if it ever fails to shut down with the key.

Fellro · Jan 23, 2008

But that's the thing, runaways aren't just a matter of the injection pump. If somehow it got an oil leak into the intake, it can run on that, and you will have no control. It varies by engine as to whether that kind of thing is a risk or not though. The old Detroits had a common problem with being able to draw oil in if you did something wrong.

blacksnapon · Jan 23, 2008

The 6.0 had the injector issues, filling the oil pan with fuel. The level would get high enough that the crank would splash in the oil, kicking it up into the ccv system, and into the intake. Body shops had to be careful with 6.0 rollovers, fix the body, start it up, and away it goes.

Kep4 · Jan 23, 2008

I bet they come apart in a big way if you can't get 'em slowed down. I bet the noise would scare the heck out of anybody near a runaway as well.

Yet another great reason to have a CO2 extinguisher in the truck.

john112deere · Jan 23, 2008

Bob Ayers said:
My Mercedes diesel has a fuel shutoff on the injector pump, if it ever fails to shut down with the key.

Interesting... I'm used to tractors with a fuel shutoff right next to the ignition key, but I've never seen anything like that in a PSD. From this thread, I gather that not all runaway diesels are burning fuel, but it still seems like a fuel shutoff would be better than nothing.

Gunner · Jan 23, 2008

blacksnapon said:
When referring to a diesel runaway, technician a says that you can shut off the motor by closing off air passages. Technician b says you can use a CO2 fire extinguisher in the intake to shut the motor off. Who's right? Tech a----Tech b-----both a and b-----neither tech

Both...........

You cut the air out of the fuel/air equasion, and no ignition.........

That being said..........The last engine I saw run away was a 399 Cat......it got a big whiff of natural gas from a well blowing out and went to about 7000 rpm...........

Now I'm not sure that you CAN cut the air off completely, but I AM sure that if you give it a good dose of CO2, it SHOULD shut it down, as CO2 will not ignite, or support ignition......

Gunner

Bob Ayers · Jan 24, 2008

Blocking the intake eliminates the O2 source, and also eliminates the ignition (heat) source.

d-kuzmen · Jan 24, 2008

Tring to block off the air on a 6.0 run away isn't easy, use the Co2. We had one here that the turbo beaings/seals failed, started drawing crankcase oil in the turbo and burning it, truck ran wide open over 6000 rpm for 20 min or more untill it couldn't draw up any oil. Want to talk black smoke, couldn't see across the shop, had to evacuate the building, people on the highway crashing into the guard rails because they were too busy watching the smoke poor out of the shop. When it was all said and done, I put 8 injectors (the tips were melted) and a turbo on the truck and fired it right up, still running to this day.! smiliegitrdone

6L PWR · Jan 24, 2008

d-kuzmen said:
Tring to block off the air on a 6.0 run away isn't easy, use the Co2. We had one here that the turbo beaings/seals failed, started drawing crankcase oil in the turbo and burning it, truck ran wide open over 6000 rpm for 20 min or more untill it couldn't draw up any oil. Want to talk black smoke, couldn't see across the shop, had to evacuate the building, people on the highway crashing into the guard rails because they were too busy watching the smoke poor out of the shop. When it was all said and done, I put 8 injectors (the tips were melted) and a turbo on the truck and fired it right up, still running to this day.!

DAMN! All that and mine blew apart! Sheesh!! I'm claimin' Warranty!! smilietease

d-kuzmen · Jan 25, 2008

6L PWR said:
DAMN! All that and mine blew apart! Sheesh!! I'm claimin' Warranty!!

Customer was lucky, his was still under warr. You just need to find a dealer that doesn't know you. :suspicious:

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