Diesel Runaway Description:

[Darrin Tosh]

I got this emailed to me, thought it was pretty good.

Found in the Discussion Board Archives (Sept 10, 2009): Posted on June 16 by Greg Holekamp: A diesel runaway is when the engine rpm goes up uncontrolled and there is no way the engine can stop itself. Diesel engines don't actually require any controls on then to run. All they need is fuel and air. Gas engines need a spark at just the right time, and a fuel pulse of just the right duration to run. Also, diesels can run on a wide range of fuel. Remember when all of us diesel guys were complaining about leaking injectors on 03's that were filling the crankcase with fuel? Well, 30+ quarts of a fuel/oil mix in the crankcase will submerge the crank. One of the last steps on the diesel diag sheet is an oil aeration test where you have to run the engine at wot (3500 or so rpm) for 3 minutes and then view the oil condition. That crank whipping up the fuel/oil will make a foam that rises through the engine, and eventually starts getting drafted into the intake stream. If there is enough coming into the intake, the engine rpm will start to rise even higher. Of course, this causes the oil to whip more, which makes it rise faster in the engine - a vicious cycle. You cut the key off, but the engine doesn't care - it's getting it's own fuel from another source. Smoke starts to pour from the tailpipe, and the truck starts to vibrate. At about 6000 rpm the ground starts to shake throughout the shop and the sales department looks outside to see if a thunderstorm is coming. 7500 rpm has the shop evacuating - by this time, the whole shop is flooded with smoke. 9000 rpm brings ominous noises from the shop - a cyclic wave of sound that feels like an invisible hand pressing on your chest. Somewhere about 10,000 rpm and the engine gives up. A sound that is a combination of a nearby lightning strike and every toolbox in the shop turning over at once explodes from the shop. The sound echos and continues for several seconds. You can actually feel a shockwave disperse through the concrete you're standing on. And then, the deafening silence. You try to see through the smoke and locate the truck - but something is wrong. It is sitting at an angle, tilted down in the front. And then you see why - both front tires are blown out. There is a scattering of parts 3 bays in each direction. A puddle of fluid is rapidly spreading from under the shredded front cap. The hood and fenders are destroyed, but ironically, the grille and headlights are still intact. And your first thought is - at least I don't have to work on this one anymore! And that, my friend Bernie, is a diesel runaway.

 

[Matrix37495]

My old fuels said they weren't really runaway diesel, its was runaway technicians....

 

[snaponprofile]

Had me on the edge of my seat.

 

[dsltech83]

I saw the original posting on the Ford technicians forum, that must be a wild thing to see- never had a diesel runaway on me yet.

 

[sootman73]

I've done this in a 6.2l before, inside my moms barn. That was 6 yrs ago. It still scares me today to start a diesel engine anytime any mod is done to the engine. I always have a board and the intake open so i can shutdown the intake of air just in case.

Always go for the air supply during a runaway for those that dont know. No air means no compression which means no ignition.

I hope no one has to live through a runaway. not a fun experience.

 

[Dieselcrawler]

Co2 extinquishers work great.......

 

[Arborigine]

I worked in a Mercedes only shop. New guy installed the vacuum shut-down solonoid on a 300TD, 3 liter 5 cyl turbo diesel. It went to full. We pinched off the fuel lines, it kept running on oil from the crankcase. We plugged the intake with rags, it kept going. It took a CO2 fire extiguisher to shut it down. It ran wide open for at least 4 minutes (felt like an hour) and when it was connected properly and restarted it ran as if nothing happened.

 

[sootman73]

Talk about it feeling like an eternity but mine only ran 3 minutes about and then blew up. i pulled a muscle in my leg on adrenaline pushing that thing out of the barn to prevent a fire. the wall of the barn is still dark black from the soot to this day.

live and learn!

 

[Black dawg]

Co2 extinquishers work great.......

I have wondered that, but have not had the chance to try.

 

[rjjp]

I have wondered that, but have not had the chance to try.

It's one of those things that you don't really want to try.

 

[Danielle]

This is one of the scariest things I've ever read!

 

[DeepRoots]

a diesel engine, even when running away will not run up to 10,000rpms. It might sound like it tho.

in Baltimore we lost a 16v149 to a runaway. Port Engineer was supposed to show up and install a governor.... crew decided they could do it without him. Everyone heard the buzzing of a 10,000lb engine spinning 5000rpms, the black smoke was pretty impressive. The crew all ran into the engine room, and 30 seconds later, they all ran out of the engine room and kinda scattered in a very non-uniform pattern. The **** was somewhat anti-climactic, and luckily the flywheel or a connecting rod didn't shoot through the hull.

I've seen other engines run away temporarily, but never a 16 cylinder 2 stroke..... most awesome (only because it wasn't my engine).

 

[sootman73]

look up runaways on youtube..... that'll scare ya. they are very loud and if you haven't been in that situation before its very hard to react effectively...

 

[Diesel_brad]

Piece of plywood on the intake opening fixes everything. Had it happen on 2 pulling tractors

 

[gunz]

Had a 4 cylinder Detroit run away on a mobile power cart. I hear the mech fire it up and heard it take off. I ran over ,pulled the fuel shutoff and the air door. neither had any effect, It sucked the seal on the air door so it could still get air. it ran for about 2 minutes before it gave up the ghost.