rightwinger

I have seen several generators blow up from going into overspeed or "runaway" and was curious how this is caused. I saw a you tube video of a dodge at a sled pull experiencing the same thing. On a diesel the air is constant, but the fuel is added to increase power, and this is done manually by the pedal.....so how would a dodge experience a runaway engine and blow up? Thanks in advance.

C Schomer

I worked at a heavy equipment shop in BF Ia. in the 60s and we had a detroit run away. The shop mngr was in the seat of this crawler tractor and the foreman and I were standing beside the engine. The mngr started the engine and revved it up and it instantly ran away. I was never around one but I was right next to the fuel tank and I was closing the fuel valve but the other 2 guys knew exactly what to do. The boss yanked the top off the air filter and the foreman grabbed shop towels out of his pocket and stretched them over the intake while the boss put his hand over the intake to choke it out. The rags were to keep the raw end of the intake pipe from cutting into the bosses hands. The pipe still put a deep red ring in his hands. Guys have been cut up and even broken hands from doing that cuz of the tremendous suction. After we all calmed down and changed our britches, we started it again and it was fine from that point on. That one was naturally aspirated and had a mechanical pump and the rack stuck. Others can have a turbo or blower oil seal leak which provides uncontrolled fuel. That's why stopping the air is the only way to kill them fast enough before they grenade or shooting a fire extinguisher into the intake. The main branch was in Ft. Dodge and they had a Cat runaway on the dyno. It broke a 10,000 rpm tach before it exploded and it threw pieces of block and rods thru an 8" concrete wall. Some diesels have an emergency air shutoff just for runaways. As far as I know, any diesel has the possibility of running away. Craig

madhat

The fuel linkage sticking is one way, ingesting something very combustible is another. I have heard of someone spilling gasoline near the intake of a diesel ( a large amount, not just a puddle) and the fumes causing a run away. Simply turning the key will do nothing, as long as she is getting a fuel source, it's gonna run: Compression ignition, the source of ignition is the pressure.

I don't agree with using body parts to choke out the turbo/intake... any time I've been around folks that know they may have a runaway condition, they have a heavy block of wood or metal near to choke out the intake. A 10-15k engine is not worth my hand. Sled pullers may have a guillotine shut off style intake choke, spring loaded metal plates in front of the turbo.

A fire extinguisher works, but only if it is a CO2. I'm sure a dry chemical would work if you had a big enough one, but the CO2 takes the fire out by displacing the oxygen.

Not the biggest expert on this subject, just stuff I've learned over the years. I'm sure I may have some faults in my conversation above...

infidel

I saw a JD backhoe run away to what seemed like 10.000 rpm when the operator hit a natural gas line.
Luckily the operator knew what was happening and drove out of the gas fumes at about 30 mph in 1st gear.

Diesels that work in some oil fields are required to have an air intake butterfly valve to shut down the air supply in case of a runaway.

SIXSLUG

We had on old CAT 3306 that ran Chair 1 at the ski area I used to work for. One of the old guys there told me it got running backwards after a failed repair attempt, not sure how but I have heard this can happen. There was a hole in the piston and it started burning its own lube oil or something to the tune of that.

Also, when we had the fuel spill here in town in 98, Whatcom creek was running rich with gasoline. A friend of mine drove over the bridge in his 86 Ford diesel, and he said he could really smell gas and his truck literally took off. He said if someone was in front of him he would have hit them for sure. He said it felt like nitrous. I imagine the intake air was rich with gasoline fumes and this powered her up.

I would suggest something other than one's hand for choking out the intake....

Red_Angus

up here all the diesel that work in the patch are supposed to have RODA Valves. its an automatic shutoff to prevent run aways. if she sucks in a combustible gas like propane or H2S, they re supposed to take off. ive never seen one do it but a mechanic told me that those detroits stove at about 3700 RPM.

Russ Roth

A CO2 will work. I had a friend lose his in his '98 Ram due to a runaway so it can and does happen. I also have a cousin who was Service Manager @ Portland Freightliner and after my bud lost his I asked Doug what they do. He said any time they have done anything that could contribute to a runaway it is a 2 man job to start the rig for the first time. One starting and the other @ the turbo with a piece of plywood to cover the turbo opening. I keep rags stuffed by the air cleaner box to try to shut mine off if I ever have one happen. Don't know if you could be fast enough but I would at least give it a try. I think it would be smart to have a flapper valve in the intake like the old 2 stroke Detroits had. BTW, Detroits and Mack engines will both run backwards. I have seen it with both of them although it never happened to me personally.

SOhappy

The Dodge dealer where I bought my first CTD told me about a customer who had a runaway when his turbo failed- he'd topped an infamous pass in this area and was headed down the other side. The engine started running on the oil from the turbo, had no choice but to ride it out until the 5.9 grenaded on him. They towed him back to the shop and replaced the engine (and other parts) under warranty - said the carnage was unbelievable.

madhat

I bet that was a wild ride...

SIXSLUG

Probably replaced the seat, too!!

SpeedyWS6

I saw a 3512 drop a valve and beat a hole in the piston. The rig savers (air shut offs) would not stop it. It was sucking the oil into the intake by way of the new hole in the piston. The flame out of the muffler was hot enough that it melted the aluminum rain cap. I had pulled the fuel shut off on the rack while the operators stuffed about 20 fire extinguishers into the intake which didn't do much good good with the rig savers closed. She finally slowed to a crawl of about 200 rpm as she ran out of oil. The fire in the muffler smoldered for several hours.

Also saw a powerstoke run away after the driver pumped a can of starter fluid in it. It didn't catch fire just reved to the moon and finally just died on its own probably shortly after it melted all the pistons.

rebal

I had 8V71 blow an injector burn a hole in the piston then runaway stopped with a air flap shut off had another 8V71 rack stick and rev to the MOON,also had a 8V92TA start up in reverse after a panic stop sorta weird feeling to have 2 forward gears and 13 reverse also had a CAT3306 start up backwards and we had a Cat 700hp V12 scatter after grinding through a gas main luckily it never caught fire,probably the A/F mix was to rich for an explosion .also had a 5.9 cummins take off after turning in the fuel screw a bit to far ,there are a few ways to have runaway

Indiana0331

my past two power strokes (7.3 & 6.0) have dieseled themselves. though it only happned a few times i never had to really do anything other than just let them run themsleves out of the fuel in the line. the 6.0L however would not only diesel itself but rev itself sky high before finally dying. I've since gotten away from Power Strokes due to 6.0 draining my wallet all the time. Thanks Ford for replacing 7.3 with a motor that gave me NOTHING BUT PROBLEMS!

Lil Dog

Yup. Runaways aren't funny. Read a whole refinery in Tx blew when a service truck ran away.

Working near gas equipment in Alberta needs one of these..

autocar56

Runaways are never good , when they run backwards that's always crazy,not good either , smoke out of the air cleaner , no oil pressure. Only seen mechanical engines do it.

Steven M