What Is A Diesel Engine Runaway? *EXPLAINED* 

In the early nineties this happened to me twice with a new ford heavy duty! They are amazing stories happening on one of North Americas busiest highways! It was like that scene in the movie Days of Thunder with all the smoke!

I was about to ask why aren't the spark plugs just disengaged, didn't even realize diesel engines don't have spark plugs

2 years ago I had a Deutz in an 820 Fendt run on me at a customer's. The customer called the shop I work at to have a tech go out and get it running after they overhauled the engine. They couldn't get it started. This particular engine has 6 unit pumps that are hooked up to a rack that opens and closes the pumps in relation to the throttle input. Controlled electronically. They had the pumps out and reinstalled them and said they were all in time, they went through the procedure in the Deutz book. I check a few things over and start to work on getting it running. I was bleeding the air out of the system and noticed I had 3 pumps pumping a lot of fuel and three that were barely spitting fuel. I tightened all the lines and cranked on it and it started. The RPM went from crank to the moon in a blink! I jumped over the front axle cause I was standing face to face with a screaming cold engine! Because I knew it was a fuel run away I cut the fuel line feeding the pump. The three pumps that were pumping a large amount of fuel were not hooked in the rack properly and were wide open! At the end of the day it needs to be over hauled again cause it had spun a couple main bearings.

As a heavy equipment mechanic in the military we kept the covers from everything. Turbos, hydraulic cylinders. We used to tape up the old stuff with metal tape or cardboard and duct tape. We kept the covers for exactly this. I seen one run away once. Old Detroit engine. After we found it was sucking up oil. Fun rebuild after wards. Stop the air stop the engine. Scary to witness.

You can't shut off a diesel if it goes full on.
Just no way you can do it.

I know engines well.
Some can be scary.
I am very proud of many.

I was so (unreasonably) worried about this issue I ran a hose from a 2.5lb CO2 accessed from inside the cab to a port I machined that sits inside the intake plenum just in front of the turbo entry. If I get a runaway I open the tank valve and it floods the engine with CO2. Yes, it's overkill but I'm retired so I have the time and money for overkill. This is on a 1988 Land Rover 110 with a 300 TDI.

I have never owned a diesel vehicle, only drove it once at the previous job but never ever experienced a runaway thing... all in all it's a good tip to help someone else who might get in trouble like that, at least I will point in the right direction to stop the engine, thank you.

I have an '85 Mercedes 300 CD Turbo Diesel. As far as I know, ALL of the MB OM series diesels have an emergency STOP lever mounted on the throttle linkage. You can't miss it. So, I guess even tiny 5 bangers can run away. I cannot think of another reason why they'd put that there.

I’ll keep a turbo cap in my center console every day

We had a runaway on a Cat 330 track hoe one time, but it wasn't an oil based runaway. What happened was the operator hit a natural gas line, and so the motor was sucking natural gas into the air intake. There was nothing we could do. Everyone was running from the broken 4 inch gas line. I don't know exactly what failed on the engine, but it revved up real high and then locked up.

I think I saw this happening yesterday on hwy 401 in Ontario. There was a truck stopped on the shoulder that I initially thought was on fire, but as I got closer I could see all the smoke and flames were coming out of the exhaust stacks. I could smell it from quite far away and the amount of smoke was outrageous. I'm assuming the guy got out OK because it was stopped safely off the road.

In a drag application, I would make sure to have something strong to cover the turbo with me. In normal applications, the diesel run away would go a lot more gentle compared to a 1500hp engine right after a intense race. In a normal car I would choose to let de transmission take the fall instead of the engine. In a drag car with these huge 2000hp+ engines, you can only cover the turbo. The thing is, you have to be able to reach it. If you let go of the clutch, it would probably destroy both the engine and transmission. you got to be prepared for it. You only have seconds to act. In a situation like the first video with the black truck, there was nothing he could do. It would be to dangerous. I guess if you have a diesel car for extreme applications, you have to invest in a electric cover valve as shown in the video. Compared to all other investments it would be more than worth it!

I had this happen on a 2 stroke jet ski. Throttle got stuck during a bench test. I pulled the kill lanyard, it kept going, i ripped off the plug wires, it kept revving higher! My dad finally ran over, he ripped of the filters & stuffed a towel into the open carb, that finally shut it down.

Just seems like such an absurd issue

You still want 25 for it?

New fear unlocked for my beloved 20yo Passat 🥲

Remove the air filter and block the intake with a rag

LOL!

Awesome vid! Even tough i knew what a runaway was about i learned à lot through that vid. The begining was pretty funny too!

we're both running away then..

An analog runaway deadlock could prevent further damage, but good luck developing that.😅 I suggest a bimetal switch like the ones in modern electronic waterboilers and a solenoid valve on the fuel intake, engine gets too hot, boom no more drinks served 😅

My guy the last thing I am doing is going anywhere near the engine 🤣🤣🤣

engange clutch + shift to 5th. Like some legend said, the car would choke to stop

I saw one start to run and i was young and did not know what to do some old guy emptied two fire extinguishers in to the air intake at the same time and that killed the runaway spooky YEA
i was told that this works never saw this agean and so not want to

Definitely engine shutoff button that’s accessible through the cabin.

Can it runaway while driving? Sounds scary.

Caterpillar and Perkins use air shut off valves in the test cells because of certain issues that can’t be mentioned.

Had it happen on a gas snowmobile, had to cut the gas off

Year old video, but I've a marine diesel with decompression valves on each cylinder. Pretty sure tractor engines have them too.

That is the fastest, most effective way to shut down a runaway and it's beyond me why truck engines don't have them.

Man I hate hearing the words, she’s runaway ! I watched a V12 Detroit gen set take off, I watched guys try to run through a wall 😆 damn. I pulled the flapper, luckily that shut her down. Check the rack I told em, oh it’s fine they said 🙄

The other day i was mount my modfied bosch pump on my ford 1.8td and i started it up and it ran away i was scared shitless my first time it has ranaway so i remembered the lever on my pump that cuts of fuel and that solved the problem

Running the fuck away

Glad my farm tractor is N/A lol

some old Detroit Diesels had emergency intake shutoffs from factory for this situation at least that's what I've heard.

That glowing red hot engine block was horrifying

I would run away and cry

Great video! Had this happen on an only late 70s single cylinder Yanmar inboard on a boat I owned. My buddy and I had no idea what was going on. Super scary. Luckily, we already had the stairs/engine cover off and somehow in our panic I thought to pull the choke cable in the opposite direction which acted as an emergency shut off. I had to do this manually by reaching my hand into the enginer compartment...RISKY, but saved our enginer and boat! Still totally wild to see it happen in person.

I actually like that electric switch idea for being a killswitch. I'd definitely want a manual override on it though so I could manually close it if needed....if I bought a diesel that is(no personal use for one). But still a good idea either way.

As much money as goes into the a diesel why would someone not install a shutoff valve.

That electronic air shutoff should have been factory installed

I’ve seen a video of some guy shoving his shirt in the air intake to choke out the engine

Lol, best intro skit!

I had a diesel engine runaway once. Reported it to the police. He never returned home

this is why me is going electric now F150 lightning!

Not an expert, but if air intake valve does not exist or has malfunctioned, can activating jake brake help? After all it is used as engine brake in tractor trailers as effective way to slow down?

It is nice to always have a CO2 fire extinguisher handy, deny the machine oxygen.

Worked in a shop in Alberta Canada, don't know exactly what the boys were doing but a diesel ford we had in ran away on us. Old Bob the foreman threw a phone book into the turbo to choke it out.

If my diesel ran away I would probably start by putting flyers up around the neighborhood.