Welcome to Dieseltruckresource.com, odds are if your reading this your new to the 1st gen Cummins. I am going to explain what runaway is, what causes it, and how u stop it!

What is a runaway?
A runaway can occur while turning up the fuel on the VE injection pump, the reason they run away is that the control collar can't move far enough towards the "defuel" end of the plunger (making the spill port area smaller), and the backpressure in the spill port becomes high enough that engine speed goes out of control. This is why they will idle OK but then hang at high RPM. At low RPM there's not enough backpressure to start the runaway.

How do u prevent a runaway?
With this procedure you can help prevent a runaway better then the old method of slow increments.
With every 1/2 turn of the fuel screw, snap the throttle. IF the throttle hangs in the upper RPM's before coming back down your on the edge of runaway, or if it will not comeback down to its prior RPM, back your fuel screw back out at least 1/2 turn.

How do u stop a runaway?
Remove an intake somewhere on the engine, if your doing this by yourself, open the intake on the driver side of the engine, if 2 people, remove the intake at the turbo and give your sidekick the board to cover the inlet into the turbo. What your doing is choking the engine should the runaway occur. This will the engine down.
You need to keep a sturdy board handy while your turning up the power, after all u dont want plywood sucked into your motor at 6000 RPM's do ya?

This is runaway, and thats how u can try to prevent it, and stop it. Still want to turn up the power??

 

YUP!!! Thanks for the info.

 

turned mine up and up till it ran away, then turned it down just a tad,
Just where I want it!!!!

 

Great post, needs a sticky in the tech facts section...

 

Does a run-a-way engine just get faster and faster, until she blows; or, is the speed still governed by the governor-spring??

Will shutting the fuel off, via a valve in the line, shut it down as quickly as the board method??

I am assuming the manual shut-down lever will be in-effective, right??



As to using a board, I would think that a healthy section out of the side-wall of a BIG tractor tire would be more effective and seal things off better than a flat stiff board.

 

The engine just takes off like a rocket untill something lets loose, a rod, crank snaps in half, u get the point. The sky is the limit till she blows!

I am uncertain on the shutdown lever, I have been told that cutting the air into the engine is the ONLY way to stop it.



N yeah, I was goin fer sticky too. I was talkin to dave n he said to post it up first.

 

You could also smother it with a Co2 type fire extinguisher emptied into the turbo inlet.
But it MUST be a Co2 and NOT a dry chemical type.

And what ever you do NEVER NEVER NEVER try to stop it by covering the turbo with your HAND.

It will suck it in and shred it before you realized it was gone.

I have seen this happen. The mechanic tried to block off the air with a shop rag in his hand and tried to cover the inlet, this was on a Detroit 8v92TA.

Jim

 

So..... would it be a better procedure to have the air intake open and a person standing-by with a board( or i like the rubber tire idea) as a safety prior to making the adjustments?
cheap insurance?

JR, you might want to add that a runaway can also be caused by being in an enviorment where there are excessive hydrocarbons in teh air, teh engine will burn those even if the fuel is shut off. Oil feilds, fuel stations or too close to an open propane source ( torch i.e.) are examples.....-

 

They hit a big gusher of crude-oil, a few miles from here.

It was coming out of the ground so fast that they were trying to dig ponds with dozers to contain it.

Several of the dozers and pump-trucks got too close to the well, and their engines got to breathing the fumes and would run away uncontrolably.

 

According to the late Pastor Bob, he tested runaway on his and it would hit 3800 RPM and hang - so apparently the governor gets some control eventually. However, 3800 RPM is enough to float the valves unless you have the 60 psi springs installed.

A fuel shutoff is not as fast and can starve the VE of much needed lube. Air shutoff is better.

Manual lever is ineffective because it's doing the same thing as the governor.

When the engine is running away and you try to use the key to kill it, it will just rip a chunk out of the plunger and keep on going.

 

Small increments work well enough. They will start to "hang" before they want to just run away when started.

If you've made major adjustments it would be foolish not to have an intake open and a board ready.

So in my opinion, "better" depends on what you've just done to the truck.

 

when i was very young starting out wrenching always heard the stories on the detroit diesels running off. they would pick up the oil in the pan and go nuts. also heard about the guy who used a phone book to cover intake and it got sucked into the turbo.

 

The two-stroke Detroits can kick over and run BACKWARDS.

Many confuse this with a regular runaway.

I recently witnessed a tri-axle dump, with a 6V93TT Detroit, run backwards.

I was waiting behind the guy, to turn and back into a dense-grade spreader-box, in front of a dozer.

There was a steep hump, that the driver had to run the front-end up on, in order to make his turn.

The engine choked down to the point of almost dying, and, my guess is, the truck rolled backwards a little, with the clutch still engaged, and rolled started the engine BACKWARDS.

There were about a dozen guys, all more familiar with such situations than I was, all over that truck in seconds.

It was puking out antifreeze, smoking like a locomotive, and sounded on the verge of flying to pieces.

I don't know what those guys did, but they got it shut down.

They fooled around some more, and to my surprise, got it started and he spread his load and went back for more.






As to this turbo blade business, would not one be better off to open the intake, somewhere between the turbo and engine, rather than work so close to disaster??

Or does the turbo need be connected, in order to make the adjustments that precipitate a runaway??

 

It's just easier to disconnect the intake hose, no reason you couldn't pop off an intercooler tube to do the same thing.

 

I've seen hummers run away... it ain't pretty. They make their own fuel by eating the oil, usually when one runs away, if we don't have co2 handy, we just stand back.