Help Me Better Understand About a Runaway Diesel

[n_hall]

How concerned should I be about a runaway on a 2017 RAM?

Is this something Cummins has resolved over the years?

From what I understand blocking off the intake and starving the engine of oxygen is the best way to stop it.

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[cumminsdieselfreak]

Whoaaa, how come you're worried about a runaway diesel?

In my opinion it's not anything that I'd ever worry about with your truck.

Last runaway diesel I remember within the last 20 years was 1 Duramax, other than that it was old Detroit's.

My advice, if i were you I'd be more worried about what I was going to have for supper tonight than your diesel running away.

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[n_hall]

Works for me.

Thank you.

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[Polaraco]

Whoaaa, how come you're worried about a runaway diesel? In my opinion it's not anything that I'd ever worry about with your truck. Last runaway diesel I remember within the last 20 years was 1 Duramax, other than that it was old Detroit's. My advice, if i were you I'd be more worried about what I was going to have for supper tonight than your diesel running away.

Nailed it.

But if you must know, block the air at the turbo intake with a thick piece of plywood or 2 X 6.

If you try to block at the filter, there's a chance you could swallow the plastic duct.

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[SyN]

I actually didn't know how to take that question - would the engine actually start on its own & engage & move?

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[cumminsdieselfreak]

I actually didn't know how to take that question - would the engine actually start on its own & engage & move?

If you've never saw a runaway diesel, YouTube it, seriously.

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[SyN]

Ok - will do!
Ok now I feel really ignorant! I'm probably the only member who had no clue what truly this subject was about!

I guess all my years around diesel engines & other diesel owners - This subject was never talked about or was it brought up in conversation. I guess my concerns were directed towards different issues...

For others who didn't know - don't admit it... Here is what I found.



Learning something new everyday.. Thank You CDF

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[BrentM]

I remember having emergency shut off levers on my Dad's boat that had Detroit 671's.

Never had to use them but they were there and they worked.

We tested them every once in a while.

They activated a flap that shut off the air into the engine.

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[cumminsdieselfreak]

I remember having emergency shut off levers on my Dad's boat that had Detroit 671's.

Never had to use them but they were there and they worked.

We tested them every once in a while.

They activated a flap that shut off the air into the engine.

Yes sir, exactly.

Killing the air supply is the only way to stop it.

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[Aboshan]

Runaway diesels are mostly a thing of the past.

They were a problem with the older Detroit 2-stroke scavenger diesels in large trucks.

These engines needed a blower/supercharger to operate.

The blower pressurized air boxes on the side of the block connected internally to the cylinder wall so when the piston dropped down it would vent the exhaust and bring in fresh air in one step so the piston fired every up stroke, thus making it a 2-stroke.

The problem would arise when the oil seals on the blower bearings would leak engine oil into those air boxes.

Usually after sitting over night allowing the oil to pool in the air boxes once the blower built enough pressure to start pulling the engine oil into the cylinder it would accelerate uncontrollably as it had its own fuel and air supply.

I had this happen to me once in 1988 in a Ford F9000 with a 6V92 2 stroke Detroit.

When it starts the burning oil makes a whistling type sound and it blows right past the governor.

This truck had an emergency air block off plate which I activated at 2600 rpm.

This was a 3/8" steel plate and it bent the plate from the vacuum but it did stop the engine.

Replaced one bent pushrod and the blower seals.

Luckily everything else was OK. It was definitely a unique experience.

What I find odd looking back is this issue was so prevalent most trucks had the air block plate.

Something that probably wouldn't pass safety standards today.

Most modern diesels with intercoolers would be insulated from this effect.

Unless there was some way to leak engine oil into the intake or cylinders it would probably be a rare event at best.

Unfortunately with no way to cut off the air the engine would continue to accelerate until the oil was gone or the engine blew...usually the latter

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