Can this happen on a 02 Cummins 5.9 with a "high tech" VP44? I don't understand how a combustible fluid like starting fluid can cause this. I can see a short term burst of rpm while the ether burns off but as soon as it's gone the vp shouldn't feed it anymore fuel than to keep idle going.

Here's the scenario: I'm stupid and the engine won't start. I spray some ether into the intake and she fires right up but continues to rev until it throws rods and chunks through the block and fender causing everyone to dive for cover.

Can someone explain what causes run away and what exactly happens?

 

too much of whatever flamable substance that was in the intake. A diesel will run on just about anything flamable that is introduced through the intake. Engine oil, either, what ever. The more you put in the faster the engine revs. We had a garbage truck with a front load container get right at the intake pipe on top of the cab and a can of paint busted and got into the breather. did the same scenario you just described. Enough gas fumes in the air can cause it. Most chemical plants wont let diesels drive into them for this reason. The pull them in and out.

 

To increase RPM on a diesel just add fuel. Then the boost will come up and then need more fuel. Like DmaxEter said if you take away the control of the fuel (by some other flammable source) you loose control of the RPM.

The ECM limits the RPM. While it is theoretically possible for a failure to occur that could cause the "run away" it is VERY unlikly.

Randy

 

And those diesel trucks that are permitted to drive in chemical plants, oil refineries, and such MUST be equipped with a mechanism that will shut off the air flow to the intake. Another good example of a runaway situation is a backhoe or excavator digging and hitting a natural gas line. With the abundance of fuel and no way of controlling it the engine will exceed its max RPMs (sometimes RPMs will reach 10,000+) for a while until the engine has a meltdown and destroys itself.

As far as ether and our engines are concerned please refer to this thread.

 

Diesel power vehicles or equipment that go into chemical/refineries or drilling rigs must have a emergency intake shutoff. The Mack RS600 I drove with the Maxidyne engine had a intake shutoff because I deliver fuel to inland drilling rigs.

MikeyB

 

For interest sake... How do you go about stopping a runaway? I know you have to restrict the air to an engine because sometimes restricting just the diesel fuel itself isn't always enough. So if you have an automatic that's on the way out and you want to stop it... how do you QUICKLY go about doing this?

 

A more common runaway is not one that runs away on the diesel fuel itself, but one that finds a source of fuel somewhere else, aka a blown turbo seal , once that engine gets a lick of the engine oil , game over, it sucks up more and more , faster and faster , until you reach a point in the rpm ( 10 000+ as stated before) where the engine either runs out of this fuel source , or destroys itself , usually with a load bang , and scattering of parts. Since it is not running on the diesel fuel , the only way to shut it down is to block off the air intake.


I witnessed a video at college of a V style detroit runaway, it was staged on purpose , for training, at about 15 000 rpm , the crankshaft vapourized.....

 

Run aways can be prevented with a positive air shutoff.

 

I know using any type of starting fluid is a big no no just for this reason. I dont think the dodge's say it but the old chevy's with the 6.0's or 6.2's or whatever the prediesssor to the 6.5 was had warnings all over the air filter.

 

When I was in the military, we used a lot of mobile generators to power com gear, radars and such. A lot of them were diesel powered. We all received training on the various units, and one in particular that I remember was called a PU-549. It was a small, single cylinder diesel powered unit. There was a four step process if it started to run away:

1. Shut off the fuel

2. Shut off the air

3. Throw the compression release

4. Run like he**

Step four was allegedly never needed, since the compression release always worked.

One day, a bunch of us techs were 'working' in our shop at the base. The generator shop was across the street, and a few power guys were working outside on a PU-549. We could hear its distintive pop, pop, pop inside our shop. All of a sudden, the pops got a lot more frequent, and people starting shouting. I stuck my head out the door just in time to see the power guys scattering like jack rabbits. A few seconds later, the PU-549's con rod let go and pieces and parts went flying.

So much for the compression release always working. Entertained and educated, it was back to 'work' for us. The power people got to play hot metal pick up.

 

Just to make this clearer, a diesel engine does not have a throttle plate, as gassers do. The intake is wide open, form the filter to the cylinders. Any form of fuel that gets into that area unregulated will cause engine overun.
The big thing about starting fluid is the glow plugs or heater grid can set it off, before you actually get to starting the engine.

Chris

 

The reason for not using either isn't because of runaway but rather explosion.
Any engine that has engine preheater such as glow plugs or our grid heaters can ignite the either before it gets to the cylinders. With the heaters disconnected there is no problem using either, the only way you would get a runaway is if you kept on spraying the either while the engine was running. As soon as you let up on the nozzle it would stop.

Very common cause of runaway is a backhoe hitting a natural gas or propane line. Best advice is to throw it in reverse and get away from the fuel source.

 

Reminds me of a story my dad told me about my great uncle.
He was plowing some low-lying bottom ground w/ his 4010 John deere diesel, went down in a hollow where an oil pump flare had somehow been extiguished. The Tractor sucked up the natural gas fumes, and took off like a lightning bolt! By the time he got to the top of the hill, the engine was probably seeing 4,000 RPM, and throwing the dirt out of the furrow about 4 or 5 feet. I think he waited for a windy day to go in there and re-light the flare, before he finished plowing that section.

 

I don't know how quickly you could do this, but a long shot from a CO2 fire extinguisher at the intake would stop it. Another good reason to shut down the truck while re-fueling.

 

To stop a runaway diesel (or any engine) take away one of the things that make it run. Spark (not a diesel engine), fuel, or air.
If you are in a situation where you can't stop the engine use a fire extingusher (preferably CO2) in the intake. The engine will be toast, but it WILL stop.

I was in JR High on a school bus trip when the driver stopped the bus and got out with the gas engine WOT. I mean this baby was ready to blow! The exhaust manifold were cherry red! He could not figure out how to stop it when I calmy walked up to the front of the bus and turned the key off. I got an award for quick thinking!