How often do diesels "run away"?

[Rock knocker]

I've been around diesels most of my working life, and have never seen it happen, or heard of it. But it seems like a persistent concern here. I have a old JD 950, and to choke off the machine from air would be a real project.

It's a totally mechanical system, are they safer or more prone to run-aways than solenoid machines?

 

[Egon]

The Diesel engine can "runaway" if there are combustible vapours entering through the air inlet. The diesel has no air restrictions.

What can be done is put a valve that can be closed inline on the air system. This is usually a clip gate type valve. There are various means of operating the valve.

Many refineries or similar type plants have a air shut off requirement for diesels. :

 

[phcaan]

I've been around diesels most of my working life, and have never seen it happen, or heard of it. But it seems like a persistent concern here. I have a old JD 950, and to choke off the machine from air would be a real project.

It's a totally mechanical system, are they safer or more prone to run-aways than solenoid machines?

I don't have any experience with tractors but in the 80's I owned a Diesel VW Rabbit. On a trip from Wyoming to California the rabbit began to run on it's own crankcase oil and I could not shut it down. Luckily it was a standard transmission and I was able to put into 5th gear and use the brakes to kill the engine. No fun and I would never care to relive the experience.

 

[JimRB]

The scary joy of an old Rabbit is a 50-65 HP Diesel Rabbit engine you could kill with the right gear and brakes. Not so sure if that would work with the more modern 90-120 HP VW 4 cylinder I have and I have no hope if my 300 HP 600 lb/ft Cummins ran away. By the way that old Rabbit was mechanical fuel injection not unlike my Jetta. Cummins has little injectors under the valve cover I think running of the camshaft. I never removed the valve cover on the Cummins but it is quieter than the old Cummins that used the same style pump my Jetta uses.

 

[jaydee325]

I would say modern diesels today, never.

Back in the day when I was in fuel injection class at Ferris State, we were learning how to adjust the fuel rack on a 6-71 Detroit Diesel. When my buddy got the rack adjusted, the instructor suggested we hook a battery up and fire it up in the lab. He had the rack adjusted to tight on one of the injectors and as soon as the engine fired, the rack stuck at full fuel. The lab filled with a roar and thick smoke. We all dove for cover. Fortunately, my buddy stayed with it and tripped the emergency trip, which was basically a spring loaded clapper valve over the inlet of the supercharger.

When the smoke started to clear, we hear the instructor laughing! He said, I saw 15 students run away but only one diesel. We all got a pretty good laugh out of that.:laughing:

Bob

 

[Ivan49]

When I was in the Army in the early 70's all of the heavy equitment we had that had a Detroit Diesel engines we run with the air intake cap loose so it could be flipped over in case of a run away engine. I saw one run away in a trenching machine and in a 20 ton trk mounted crane. I was in the cab of the crane at the time and I can tell you it is enough to make you fill your pants having to go in the back to flip the intake cap over. I have seen the results of an engine that sucked all the oil out of the crankcase also. The newer equitment that came thru the shop had the flap valve in the intake.

 

[Egon]

I would say modern diesels today, never.



Old or new when they get an unlimited fuel supply through the air inlet they will just keep on revving up.

In most cases the same Diesel engine only runs away once!:thumbsup:

Diesel Engine Air Intake Shutoff Valves
Model RDS5 High Temperature Electric Swing Gate Valve
Overview
If flammable gas or vapor is present in the atmosphere surrounding a diesel engine, it can be ingested into the engine and become an ungoverned fuel supply. This ungoverned fuel can result in runaway engine overspeed, potentially leading to dangerous mechanical failure or an explosion.
The Roda Deaco RDS5 Swing Gate Valve is a positive spring actuated air intake shutoff valve that provides emergency overspeed shutdown of a diesel engine. The RDS5 Swing Gate Valve can be triggered to close, which starves the engine of air and shuts down the engine.
Model RDS5
High Temperature Electric Valve



Reliable protection from
diesel engine overspeed
During operation of industrial and marine engines, combustible vapors present in the operating envelope of the engine can be drawn into the air intake. This provides an additional source of fuel. Intake of this va- por can result in loss of engine control. Loss of control can also be the result of a failed drive train or sudden loss of a coupled load. Attempts to shutdown the engine by standard control systems such as normal fuel shutoff will not stop the runaway condition and prevent serious engine damage, personal injury or catastrophic results.

 

[powerpace]

Years ago when I was in the Fire Department we had a area that was served by Portland, Or., TRIMET bus lines. After having a emergency on one of the buses we were given a quick what to do/not to do class a few weeks later. The first thing the mechanic said was flip the air shutoff if there was a fire or engine problem. The second was "do not crawl or reach under the coach. It seems the frame may go within a few inches of the ground if the airlines are compromised.

 

[psj12]

I was a diesel mechanic most of my life and only had one true runaway. It happened in 1972 on a WW II vintage landing craft that belonged to some researchers from Hawaii University who were stationed on Christmas Island in the Pacific. I was in the Coast Guard and we were there to work bouys around their small harbor and our captain said we would repair the LCM as a favor to them. The Landing craft was rusting away and had holes in the hull everywhere. When we finally got one of the old Grey Marine (later to become GM then Detroit diesel) 6-71s to fire up it had a bad blower seal and started running away on lube oil. The old Grey Marines had no emergency air cut off so I slapped a clipboard to the blower intake and then dove for cover. As soon as the rpm dropped the vacuum holding the clip board in place dropped and so did the clipboard. Then it really ran away until it tore itself up. Rods, pistons and crank all broke. We then used the LCM as a barge. Later that night it sank from all the rust holes in the hull.

 

[grm61]

detroit 4-71 in gmc 650 running away start after the 30 years - YouTube
Shook up the young kid pretty good.

 

[Ilikeurtractor]

There was an explosion caused by a gas leak (I think a methane source) that entered into a diesel truck causing it to run away and explode similar to earlier examples in this thread a few years ago here. It was pretty ugly.

The thing that always amazed me is how good a diesel can apparently run off a flammable mixture coming through the intake although I haven't actually witnessed this myself other than cold starts off ether. One might think that the horrible timing of the combustion wouldn't allow it to run very well (extremely advanced?) but apparently it's not that much of an issue. I suppose once it begins to hit higher revs the advanced timing aids in going to higher rpms as long as the fuel and air supply are there to support it.

 

[yelbike]

I remember as a teenager working in a marine dealership. The shop mechanic told a gas engine could diesel and overspeed as well. I guessing same way, aspirate fuel?

 

[tlm720]

I had a bit of a scare with my JD720 after rebuilding the top end. I knew there was a possibility of not getting the governor connected properly and I still did it anyway. Had I thought about it ahead of time it would have been as simple as pulling the compression release. Instead I paniced and got stupid. Eventually I put it in 6th gear and killed it. No harm done other than to the governor. It tore the weights up pretty good after they flew out so far the lever arms came out from behind the thrust bearing.

 

[Mechanos]

On an engine that doesn't have an air valve shutoff and has an intake arrangement that is not easy to get to choke off, there is another option... you can flood the air intake with CO2 from a fire extinguisher to starve the engine of oxygen.

 

[MHarryE]

We had a problem at Deutz-Allis after introducing one of our first Deutz engined combines. Allis-Chalmers had only a vent hose for crankcase ventilation but the Germans with tighter environmental restrictions had a closed crankcase ventilation system. Sure enough the hydraulic pump we used had a defect that resulted in internal leakage that the flow path couldn't handle so the double seals both blew, hydraulic leakage got dumped into the engine, the level got high enough for the crank to really churn it to a froth that went through the vent system into the intake manifold and voila! The engines would take off uncontrolled. I ot to talk to one customer when he came to the plant to pick up his new engine. He said the engine just started screaming so he knew something was wrong. He went to the ack, opened the hood and that really scared him so he ran as fast as he could to get away before it exploded. Fortunately instead of exploding the engines either seized from the heat generated or died because the oil mixture got too rich to burn. Beginning of harvest season in the corn belt so talk about a crash redesign to remote mount our old proven belt drive pump.

 

[Baby Grand]

Someone on here had a runaway after his tractor tipped over and it started ingesting crankcase oil. Trying to remember who that was. Got it :
http://www.tractorbynet.com/forums/kubota-owning-operating/179496-rolled-my-3240-ran-till.html

 

[Fan of the 1911]

I had a Detroit runaway backwards, it blew the water separator and the fuel bowl off of the side, and started to run off of crank case oil. I jumped on top of the cab and used my Kevlar to catch the flapper valve down on the exhaust and stood on it with one foot till it died.:shocked:

When it went wide open with that spooky wide open howl I almost wet myself.

 

[Scooby074]

detroit 4-71 in gmc 650 running away start after the 30 years - YouTube
Shook up the young kid pretty good.

That was awesome. Its wrong but I got a smile on my face. Laughed at the old guy,.. while the kids are nowhere to be seen, he walks over like "whats the big deal" and plugs her up.

 

[Scooby074]

Heres another good runaway video. New or repaired turbos I think was the cause. Got to love the boss on the phone telling him to go shut her down... "I aint pullin that hood open"!! No kidding:thumbsup: