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Remember you're a womble
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Discussion Starter · #1 ·
Had an interesting experience at the weekend so just looking for some pointers, advice and the usual useful suggestions that always come from Sailnetters :p
Anyway, I was motoring out of the harbour, normal cruising revs which on mine is about 2800rpm, had the main up as I was going to sailing shortly. There was a clunking, sounded definitely transmission related and I had something similar previously (which I thought I'd fixed but there you go). Throttled back and into neutral, I have an Edson single lever control, back into forward, throttled back up and all fine again.
About 30 seconds later, same clunking, this time when I throttled back the engine revs climbed, and climbed. Back into neutral and off she went, revs up and up. I pulled the kill lever, no effect.
Mildly concerned by a hundred pounds of pig iron trying to destroy itself under my feet, I went below to pull the access covers off to get her stopped. Of course there were a bunch of things in the way so it took me about 30 seconds (a guess, time has a strange way of deceiving you in these situations).
Just as I was pulling the first access cover off, the revs dropped back down as if the throttle had been closed, and then she shut off (same as she does normally, kill lever was pulled remember).
She had revved so hard that one of the water hoses was starting to come off. I tightened everything up, checked what I could see and there was nothing obvious causing it.
After mulling my options, changing my underpants and so on, I fired her back up again, took a few seconds longer than usual but she fired and sounded pretty normal. I motored back to my slip at just above idle.
Went back to the boat Sunday and took the engine control covers off, all looked spotless in there, everything seemed to work smoothly. Couldn't see anything obvious anywhere, only slight tickle was the dipstick touching the throttle lever on the engine when the throttle was open. Bent that out the way. Fired her up, let her warm for a few minutes, revved in neutral no problem, ran her for several minutes in forward at about 2k rpm (can't go any higher when tied up, the load makes her smoke like a chimney), same in reverse at 3k rpm, nothing untoward.

So.... any thoughts on a cause, how to prevent it in future, anything else I need to check etc?

Seems somehow different to most/all the other things I have read about a runaway diesel, she was running at full throttle for at least a minute or two I would think, but never got to the destructive part where bits of engine were flying off and puncturing my hull.

In hindsight, I wish I had checked the throttle was closed at the engine end because that would have at least told me it was an actual runaway, but that's hindsight for you.
 

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Good detailed post.... unfortunately nothing helpful is occurring to me - mysterious...
 

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Interesting scenario.

I think I would:
- check the oil level...check its viscosity by running it between my fingers...and smell it to see if there is diesel fuel in it.
- pull the governor cover and see if there is any obvious loose linkage or unexpected wear including fly weights and springs.

Then I would think some more and scratch my chin. And check my tech manual drawings and ponder some more.
 

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Remember you're a womble
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Discussion Starter · #4 ·
On the positive side, I now know what a single cylinder diesel sounds like at 4000rpm :D
 

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Overfilling with oil can cause a runaway as the engine burns its lube oil. Were you at much of an angle - you said the main was up? I wonder if that could cause the lube oil to be ingested if it was higher on one side.
 

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Discussion Starter · #6 ·
I was pretty much upright, there weren't even any waves. Oil was only overfilled if someone broke into my boat overnight and added some more, I did an oil change 42 engine hours ago so I'm pretty sure I would have seen this prior to the weekend, and I have motored in some pretty bouncy sea as well plenty of times.
Only think I can think of is that either it wasn't a runaway at all, rather a stuck throttle lever at the engine end or something like that, or that whatever caused it got used up allowing the engine to return to normal.
Either way, I don't really have an answer. I'll check the oil again at the weekend to see if it's magically got fuller (in which case I must have either diesel leaking into it, or the transmission oil is getting out and into the engine), take the air intake apart and see if there is oil in the filter, pull the governor cover off (will have to look in the book for that), anything else?
 

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If not lube oil then the governor could be the cause. I'm not a mechanic so just guessing.
 

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Discussion Starter · #8 ·
With a runaway, wouldn't the revs just keep going up and up as the increased revs draw in more fuel, more air and so on? I'm pretty sure it revved to a point but no further. Admittedly that point was somewhat higher than I would normally expect the revs, but then I wasn't looking at the tacho.
 

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It's not just fuel that is being drawn in, engine oil can combust too.
Your crankcase is vented through a crankcase ventilation tube that returns crankcase gases back into your intake.
If the engine is worn enough to create blow-by via the piston rings or you have too much oil in the crankcase or worse fuel in your oil via a fault in the fuel rail. You have a recipe for disaster.
The crankcase gases will feed into your intake via the crankcase ventilation tube. Once they become combustible you have a runaway condition.
You can shut off the fuel but the engine with keep running off of the crankcase gases. It will start to increase in rpm which will promote this situation and so on and so on. The engine will start to create so much oil mist that it will continue to increase in rpm until it has a mechanical failure or runs out of oil and seizes. You got lucky somehow.
I'm going to take a guess and say that there is no fuel in your oil and your oil level was a bit to high and/or your rings are worn.
If it happens again you can smother the intake, you can decompress the engine with the decompression lever or you can give it a shot with a fire extinguisher into the intake and put the fire out.
One way or the other you are going to need some engine work done.
Sorry to hear this Paul.
 

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Thinking further...perhaps you had something fouling your prop that you lost in bits or unwound in an erratic way...kelp or other heavy bio material loading her up and keeping revs down that disintegrated to allow the engine to rev higher until the governor "caught" the engine speed and brought it back down. That clunk could have been the prop/shaft/tranny loading up with the heavy load of the foulant?
 
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You mentioned the dipstick, ? If it is not sucking lube oil from somewhere, which I think might be constant,? It may be in the linkage system. You might try disconnecting all the linkage components at the engine and try to duplicate the run away/over reving.

I think if it was sucking lube oil it would rev higher than 4,000 RPM or until it scatters? The other possibility could be a bad injector pump which could be checked by a shop.

Let us know what you find, always interesting.

Paul T
 

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My thought is a sticking valve in the injection pump as well they need some type of lubrication added to the fuel now days with the ultra low sulphur fuel now days replaced the db 2 pump on my old 7.3 International and the company said I had to use a fuel adative lube or it would void the warranty. ( Thanks epa) and that uncontrolled fueling would explain all the symptoms including eventually correcting its self.
 

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Discussion Starter · #15 ·
Well, it may turn out to be one of those weird things that never gets explained, resolved (and hopefully) never happens again. I'll check what I can at the weekend and then just see what happens. If it does it again then obviously I'll have to start pulling things apart, which likely means pulling the whole engine out.
 

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Most likely, and most commonly with that engine, the fuel rack became stuck. It doesn't need to be at full load to overwhelm the governor and the runaway speed will naturally be limited by the pumps lack of advance timing and valve response. Nothing else makes sense.
Check your filters for debris, treat your fuel (lubricity) and have your pump and injector removed and inspected.
 

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Discussion Starter · #17 ·
I'll have a fiddle at the weekend. Then I'll go look at the engine. The fuel rack is the gubbins inside right? I need to take the filler cap off and poke about until I find the lever and make sure it all seems to operate smoothly? I'll pick up some diesel treatment goop as well, cleaner and lubricant. At some point I guess I'll have to take the top off the engine and check the moving parts under there, get the elbow off and check that too. And then I might as well pull the whole head off, and get the injector off for a service, and the pump at the same time.
I see oily hands and much swearing in my future, I refuse to pay a shop $100+ an hour.
 

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PIV, other than the contortions required to get to everything in the engine bay, the 1GM10 is lawnmower-simple to work on. removing the elbow, the injector, the bonnet, the alternator, etc., requires one, maybe two wrenches, a 12mm and 14mm if i remember correctly.
 

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Discussion Starter · #19 ·
Well, oil level was a touch above max so I syphoned off about 1/2-3/4 pint of oil, that put it a touch below max. Cleaned out the air filter, was a bit oily but nothing crazy, checked all the throttle levers etc, adjusted the alternator belt tension. Couldn't see anything obvious, dumped a bottle of fuel treatment/lubricating stuff in the tank as well, can't do any harm.
See what happens I guess.
 

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The manual say's your engine only holds 1.3 litres of oil. Removing 30-50% of the oil will probably solve the problem.
If the oil doesn't have a diesel smell to it then you might want to fix the lock on the companionway door. You don't want anymore people breaking in in the middle of the night and over filling your crankcase again.:D
 
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