Berak

I've heard reference to this happening in reference to getting a &quot;whiff&quot; of gasoline vapor. Can someone explain to me what happens to cause this and what the real world dangers are for a modern diesel engine like the ISB 5.9? With the electronic PCM controlled injection on the new 2003 ISB, is this even possible?<br><br>Thanks.

Shovelhead

From what I understand.......
the diesel is a huge air pump like most engines, however we have no &quot;butterfly&quot; to control the amount of air entering the engine, our Cummins only regulates the amount of fuel to control RPM.
If the engine gets an alternate fuel source (like a fuel vapor rich gulp of air) there is no way to control RPM, or shut off the engine, except starving the air source via a CO2 extinguisher, or blocking the air intake (don't try a rag or your hand over the intake tract. )
This is another good reason to shut off when refueling at your local gas and go.
If the guy at the next pump dumps gasoline on the ground, and the Cummins gets a whiff.....................well, let's just say you're in for a little excitement at best, an expensive repair bill at worst. :

Dieseldude4x4

Diesels can run away if they take in enough of a flamable vapor through the intake system (gasoline vapors, cleaning solvents, etc). The intake will in this case act just like a big carburetor and if enough concentration gets sucked into the intake, the engine will run even with no fuel injection taking place. Since there is nothing limiting the amount of vapors it is taking in (throttle plate, injection amount, etc), there is nothing to control the speed of the engine and away it goes if there is enough concentration of vapors and a steady supply. This can be an issue with any diesel no matter what controls the engine has. The computer could shut off all fuel and the engine would still run on the concentration of vapors being taken in.<br>A hot diesel can also run away on the fumes from the oil in the crankcase under the right conditions mainly if the engine is heavily loaded and the intake air is shut off for whatever reason. While it is extremely possible, it is not likely that it will happen unless a number of things are just right. There was some discussion in here a while back about shutting the Cummins down while refueling. This concern was more from sucking up gasoline vapors from a nearby gas pump more than anything. Diesel fuel vapors would more than likely not cause this to happen unless there was a very very high concentration.<br>Hope this help and I'm sure others will add to this.<br>

Berak

Thanks, I got a better understanding now. I guess the only way to stop this once started is to have an air shutoff valve somewhere in the air intake system. Do any of the aftermarket system offer a shutoff of some type?

Shovelhead

[quote author=Berak link=board=8;threadid=11343;start=0#108138 date=1046043017]
Thanks, I got a better understanding now. I guess the only way to stop this once started is to have an air shutoff valve somewhere in the air intake system. Do any of the aftermarket system offer a shutoff of some type?
[/quote]

Some one posted awhile back about a mechanical shut-off valve that is required to be installed on a diesel before they let it in the oil fields to prevent runaways.
Might try a search on here or yahoo.
You'll probably never need one if you're careful and aware of the potential problems.

Here's a little more info.
PDF doc. on Runaway Diesels

Dieseldude4x4

While it is highly unlikely you will ever need it, you could install a valve if you could find one. The main thing is to be careful around explosive vapors with a diesel. Shut it off when you fuel up if you are fueling near a gas pump. Don't run it if you are using or are near someone using fluids. I've heard of people shooting Co2 into the air intake but I'm not real sure I want to be that close to one when it is running away. You don't know how fast it's going to turn before it decides to come from together. You would have to be in a pretty vapor rich environment for that to happen, probably the most you would see it a little burst of speed till the vapor trail was burnt up or dispersed to below the flash point.<br>If you do find one, be sure and post the link in case anyone else wants to do the same.

dodgeram

had a turbo seal go once, and the motor would start sucking engine oil in when you let off the gas real fast(vacume condition) and start to run away<br><br>it would start to rev sky hi and then some boost would build up and it would stop sucking in oil and then it would die(cause I already had the key shut off ........)<br><br>it wasn't a CTD it was an 86 toyota with the toyota turbo diesel.........got real exciting a couple times till I figured out what it was ........

cp

Any compression ignition engine is subject to runaway. All it needs is fuel of some sort, because it has the air and ignition temperature already.<br><br>My VW diesel Rabbit did this twice, both times running on its own engine oil. How it survived these trips to the stratosphere of rpm's is beyond me. It's pretty scary when it happens because you turn off the fuel and nothing happens--it just keeps on revving.<br><br>A friend had a Cat engine run away on Jet-A fumes. That engine did not survive. Old Detroit 2 cycles had an emergency stop provision which cut off the air. Apparently they were prone to running on their own oil.<br>

BigBlue

That's pretty funny.

acoustic_axe

Ditch Witch trenchers use an emergency shutoff lever that closes a valve in the intake. In case during trenching you hit a natural gas line or the such. Sure makes the machine hard to start if someone accidently hits the lever and doesn't realize it. heheh.<br> Later.

Dieseldude4x4

[quote author=BIG ED link=board=8;threadid=11343;start=0#108187 date=1046050438]<br>What's really cool about the old 2 cycle Detroits is when they run backwards. I used to drive an old ten wheel boom truck with a 8V-71. To shut it off you used to pull a lever that I believed closed a butterfly in the intake. Anyway, I let off the lever just before the engine stopped rotating and the next thing I know the exhaust stack is now the intake manifold and it's blowing exhaust smoke out the intake openings on the hood. To shut it off I had to put it in gear and dump the cluch while standing on the brakes. It was a very interesting couple of seconds in that drivers seat. <br>[/quote]<br><br>Funny you should mention that. I had an old B61 Mack run backwards on me one time. I left the clutch out and the trailer brakes were frozen on. I left off the hammer before totally disengaging the clutch and just the torque from the cab settling back down stalled the engine and started it running backwards. Thought I blew up the bosses rig till I figured out what I had done.

Lil Dog

There are many Positive Air Shutoff devices on the market for all diesel engine driven vehicles. I have to get one this week for mine as I now am using it in the Oil and Gas field.<br><br>My partner just had his installed in the Duramax. Its an electronic controlled shutdown that monitors engine speed. If the engine goes 5% over the rated red line the valve closes to shut the engine down. Its installed in the intercooler line just before the intake and is a solenoid actuated slide valve.<br><br>They run for about $1800 CAD installed for the electronic version. For the same electric valve with only a kill switch is around $1200 CAD.<br><br>Most major oil companys require it to be on site. JHansen has one in his 2002 as he is an oilfield operator.<br><br>J-eh

Dieseldude4x4

Cool. Do you have a web site or anything for those interested?

Shovelhead

Joel, Try here for Cutoff valves.

http://www.rodadeaco.com/

Diesel Engine Air CutOff Valve