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post #21 of 50 Old 05-21-2013
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Re: Runaway diesel

I have not the specialized tools (torque wrenches and such) to get inside the main engine chamber. A specialized Yanmar mechanic is coming down this week. I will be on the boat during the work.
The engine will be fixed, or replaced. The problem WILL be fixed ONCE AND FOR ALL.
I will post a full diagnostic once obtained. Thank you for your interest.
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post #22 of 50 Old 05-21-2013
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Re: Runaway diesel

Originally Posted by Frogwatch View Post
Harborless's problems with a "runaway diesel" is so odd that I really want to know more. How can this happen when the Governor sets the max amount of fuel unless the governor isnt working? Bristol suggested that overfilled oil was allowing oil to be burned instead leading to runaway. Yes, I can imagine an engine continuuing to run on oil but to run away? I woulda thought that in order to run fast that good properties would be necessary and with just the oil, it isnt being injected right.
I've always found that REALLY understanding symptoms solves 90% of problems so we have to get a solid handle on them.
frogwatch, your point that in order for an engine to run fast you must properly meter in the fuel and air, and plenty of it makes perfect sense.

But in this case there is an abundance of fuel, so much so that excess "fuel" is exhausted partially and fully unburnt (absolutely tons of smoke is emitted, and raw "fuel" pours out). In the case of a runaway there is plenty of fuel and air is the limiting factor. It just happens that there is enough air to take the engine to an unsafe RPM, and discard the extra fuel.

It is truly terrifying. I keep a piece of plywood near the air cleaner now so that I can use it in the event of a runaway. But I shudder at the thought of having to use it.

It happened to me on a previous boat, a Yanmar YSM15, I overfilled the after an oil change. tarted her up, revved a bit and it ran away. I had nothing handy to stuff in the air intake. I was lucky in that case, It stopped on its own after about 30 secs with no damage. I can tell you that those 30 secs felt like about an hour!

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Oriental NC
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post #23 of 50 Old 05-21-2013
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Re: Runaway diesel

Originally Posted by Capt Len View Post
Likely candidates for runaway are the Pathfinders (V Dub Rabbit) Detroit Jimmies and some English Fords. Dilution of lube with fuel oil from injectors or the return lines into sump can be the the culprit. Dumping the PCV line into the air cleaner can have surprising effect when stuff goes bad too. Pulling the air shut down on a Jimmy will probably suck the gaskets out of the compressor but better than a drive plate through the hull . Fairbanks Morse made the 'rock crusher'
Our Jimmy was many years ago and I may be a bit foggy as to how the kill mechanism actually worked. I don't remember a fuel shut off valve, all I know was that it worked, from the wheel. As neutral was extremely hard to find on the Twin Disc clutch it was just easier to kill it once I was in.

Paul T
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post #24 of 50 Old 05-21-2013
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Re: Runaway diesel

Originally Posted by Capt Len View Post
hull . Fairbanks Morse made the 'rock crusher'
Funny thing about the Fairbanks Morse. When my Father went to engineering school in the Mid-sixties. They had phased out the training on that engine as supposedly they were all being replaced in the fleet. Ten years later, he winds up on one of the last ships in the fleet to still have them.

Art Haberland

In the end all that matters is how fully you loved, how gently you lived, and how gracefully you let go of things that did not belong to you -Buddha


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post #25 of 50 Old 05-21-2013 Thread Starter
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Re: Runaway diesel

I love diesels but never knew this could happen.
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post #26 of 50 Old 05-21-2013
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Re: Runaway diesel

A severed pressurized propane line in the engine compartment will cause a runaway diesel as well. Quite terrifying.

'79 Camper & Nicholson 303, Blow'd up labor day
Sunfish just fine
Dyer Dow, crushed in Hurricane Sandy
Angler 204 Cuddy-, Crushed in Hurricane Sandy
Yes all true, No wonder no one will go on the water with me.
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post #27 of 50 Old 05-21-2013
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Re: Runaway diesel

Some years ago I had a boat with a Yanmar 3GM30 and I had a small container in the lazerette filled with gasoline for the outboard. The gasoline leaked and found its way into the engine enclosure and just the petrol vapor was enough cause the engine to briefly run away.

It came under control before any damage was done and I learned a valuable lesson about gasoline storage.

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post #28 of 50 Old 05-21-2013
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Re: Runaway diesel

the 2 cycle gm diesels had a flapper in the intake to shut off the air in case of a runaway. if the air box drains were plugged , oil would build up till the air would blow the oil into the cylinder through the air inlet ports in the cylinder liner. then the screaming jimmy would really scream.

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post #29 of 50 Old 05-21-2013
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Re: Runaway diesel

I wouldn't mind practicing shutting off the engine by snuffing the intake. Can you harm a diesel by doing that?

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post #30 of 50 Old 05-22-2013
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Re: Runaway diesel

I took my sewing awl, some #150 thread, a button, a old teak cup holder and a old rubber ball ( old doggie toy ), I ran the string threw the ball ( button keeps string from pulling threw ) screwed the cup holder in the engine compartment close to air intake, ball sit in cup hold so it doesn't get lost and has enough line to reach intake.

May sound a little goofy but, it's there when/if needed.

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