Taking the boat to the marina for winter storage proved to be a very exciting time over the weekend. We were under sail for our 25 mile trip when the wind decided to leave us stranded about half way. We powered up and proceeded to take the sails down. About a half an hour later the diesel (44 horse Yanmar) decided to leave us stranded too but not before racing out of control. For about three to four minutes, the engine seem to rev up to full speed, almost like we lost the prop or something, and it could not be shut down until the fuel line shut off was located and turned off. The emergency shut off didn't work. We did not lose the prop and later, after being towed in and while safley at the dock, we started the engine again and it worked perfectly. It was pretty wild there for a while. Anyone ever have a similar experience? The mechanic will be checking it out but he said wasn't sure what the cause was. What can make an engine do that?
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Oil level?
Did you perhaps change your oil prior to the trip? If you have too much oil in the crankcase, the engine will burn the oil as well as any fuel available. Also, what was the color of the smoke during the runaway? That could give a clue. Last question...did the boat respond to the increase in engine speed? If not, you might be looking at the gearbox, or perhaps the sheer pin on the prop or shaft. Steve
Did you perhaps change your oil prior to the trip? If you have too much oil in the crankcase, the engine will burn the oil as well as any fuel available. Also, what was the color of the smoke during the runaway? That could give a clue. Last question...did the boat respond to the increase in engine speed? If not, you might be looking at the gearbox, or perhaps the sheer pin on the prop or shaft. Steve
oil level
Oil level was not an issue. Smoke was a white to grey color and lots of it. (It usually smokes a little anyway) I cannot remember what happened as far as the speed of the boat when the engine raced. I did try to cut back the thottle and took it out of gear as a kind of automatic response. Gear box trouble could be and option and I will have it checked.
Oil level was not an issue. Smoke was a white to grey color and lots of it. (It usually smokes a little anyway) I cannot remember what happened as far as the speed of the boat when the engine raced. I did try to cut back the thottle and took it out of gear as a kind of automatic response. Gear box trouble could be and option and I will have it checked.
runaway
As far as I know, diesel engine runaway is usually caused by excessive wear of the engine internals (rigs, valve guides, ect). The engine starts burning it's own crankcase oil as fuel, and usually won't quit running until it runs out of oil or throws a rod. The only way I know to stop one is to shove a rag into to air intake and thus starve the engine of oxygen. The fact that you managed to stop it by shutting off the fuel line may be a good sign however, the engine kill cable should have done the same thing. I had the same thing happen on an old Volvo and it threw the govenor out the side of the block in little pieces. In any case you'll need to have a good mechanic go over the engine since you're probably looking at a partial rebuild.
As far as I know, diesel engine runaway is usually caused by excessive wear of the engine internals (rigs, valve guides, ect). The engine starts burning it's own crankcase oil as fuel, and usually won't quit running until it runs out of oil or throws a rod. The only way I know to stop one is to shove a rag into to air intake and thus starve the engine of oxygen. The fact that you managed to stop it by shutting off the fuel line may be a good sign however, the engine kill cable should have done the same thing. I had the same thing happen on an old Volvo and it threw the govenor out the side of the block in little pieces. In any case you'll need to have a good mechanic go over the engine since you're probably looking at a partial rebuild.
runaway
We checked the engine oil level afterward at the dock and the oil level was good and the oil was clean. The engine started again while at the dock and seemed to run fine. We did not check the transmission at that time, probably because we were a little rattled. I will have a good mechanic check it out but my first thought is that the engine is OK. This engine typically gets very little use. We use it just to get out of the harbor (5-10 min) before we set sail and then when we return. If it gets a total of three hours of running time a season I would be surprised. I'm inclined to hope that it is a transmission linkage thing rather than an engine rebuild. Before I bought the boat the previous owner told me that he had a linkage problem putting the boat into reverse but told me that it was fixed. It's worked fine for the two years that I have owned the boat. This is a 1985 Hunter 40 that has spent maybe five years of it's existence out of the water.
We checked the engine oil level afterward at the dock and the oil level was good and the oil was clean. The engine started again while at the dock and seemed to run fine. We did not check the transmission at that time, probably because we were a little rattled. I will have a good mechanic check it out but my first thought is that the engine is OK. This engine typically gets very little use. We use it just to get out of the harbor (5-10 min) before we set sail and then when we return. If it gets a total of three hours of running time a season I would be surprised. I'm inclined to hope that it is a transmission linkage thing rather than an engine rebuild. Before I bought the boat the previous owner told me that he had a linkage problem putting the boat into reverse but told me that it was fixed. It's worked fine for the two years that I have owned the boat. This is a 1985 Hunter 40 that has spent maybe five years of it's existence out of the water.
Heeling effect
Tomm On most diesels, if you are heeled over beyond 17-20 degrees, the oil pump won't pick up. In addition to the obvious consequence of losing lubrication, you could suck air into the cylinder bores.The latent heat on the cylinder walls would volatilize the remaining opil and cause any remaining lube oil to ignite causing the problem you experienced. Not likely but I can't think of any other possibility. Don
Tomm On most diesels, if you are heeled over beyond 17-20 degrees, the oil pump won't pick up. In addition to the obvious consequence of losing lubrication, you could suck air into the cylinder bores.The latent heat on the cylinder walls would volatilize the remaining opil and cause any remaining lube oil to ignite causing the problem you experienced. Not likely but I can't think of any other possibility. Don
my bet is different!
What the engine hot. I have heard of diesels running away when over heated. the fuel fires itself and fuel shut down is the way to stop it. Never seen it my self. but ask arround about it.
What the engine hot. I have heard of diesels running away when over heated. the fuel fires itself and fuel shut down is the way to stop it. Never seen it my self. but ask arround about it.
Stuck injector
Could injector tips have gotten stuck open from crudy fuel, rust, or lack of oil in fuel? I would have the mechanic remove and pressure check the injectors.
Could injector tips have gotten stuck open from crudy fuel, rust, or lack of oil in fuel? I would have the mechanic remove and pressure check the injectors.
Andy, don't confuse diesel with gas engines
A stuck diesel injector can't pass additional fuel. I don't think modern gasoline injectors can stick open and pass a steady stream of fuel either. The only fuel the engine gets is what is calibrated into the pump at the optimum instant for combustion. This problem is a head scratcher.
A stuck diesel injector can't pass additional fuel. I don't think modern gasoline injectors can stick open and pass a steady stream of fuel either. The only fuel the engine gets is what is calibrated into the pump at the optimum instant for combustion. This problem is a head scratcher.
Runaway Easy to Stop - Use a Shoe
A runaway engine is easy to stop. My preference would be to put a shoe, sole side of course, over the end of the air cleaner as soon as possible to starve the engine of air. The reason for my preference for air starvation is because the fuel shutoff valve is usually too hard to get at and all the fuel in the line has to get burned up before it will stop. A shoe or tong is usually readily available. A common source of runaway engines is the fuel return line gets restricted or blocked: 1. Pinched return fuel line (put something on it?, Kinked?, etc.) 2. Scum buildup inside the return line like the stuff that's in the bottom of an old fuel tank. The return line only has to restrict the fuel enough so that pressure builds up upstream. The excess pressure forces fuel out the only other openings available - the injectors. The good news is there are probably no air leaks on the pressure side.
A runaway engine is easy to stop. My preference would be to put a shoe, sole side of course, over the end of the air cleaner as soon as possible to starve the engine of air. The reason for my preference for air starvation is because the fuel shutoff valve is usually too hard to get at and all the fuel in the line has to get burned up before it will stop. A shoe or tong is usually readily available. A common source of runaway engines is the fuel return line gets restricted or blocked: 1. Pinched return fuel line (put something on it?, Kinked?, etc.) 2. Scum buildup inside the return line like the stuff that's in the bottom of an old fuel tank. The return line only has to restrict the fuel enough so that pressure builds up upstream. The excess pressure forces fuel out the only other openings available - the injectors. The good news is there are probably no air leaks on the pressure side.
But John, wouldn't a stuck, high pressurized return fuel
line blow untimed fuel into the engine, thusly contributing nothing to the needed precise timing required for diesel combustion? How could that cause such high, runaway speeds? (maybe if the top end was soaked in raw fuel?) Besides, the return line is rubber and hose clamped on. It should blow off it's fittings under high pressure wouldn't it? But what do I know at this hour?
line blow untimed fuel into the engine, thusly contributing nothing to the needed precise timing required for diesel combustion? How could that cause such high, runaway speeds? (maybe if the top end was soaked in raw fuel?) Besides, the return line is rubber and hose clamped on. It should blow off it's fittings under high pressure wouldn't it? But what do I know at this hour?
Thanks everyone
Thank you all for your input. I will discuss all these responses with my mechanic and let everyone know as things go along. I'm just not sure how long this will take to resolve. If it helps, this is a fresh water boat and has never seen salt water. The engine always starts immediately when the key is turned even after sitting all winter. The engine smokes some with a whitish color or grayish color smoke which increases with more throttle but the oil level is not affected. Because we use it for only short periods of time (in and out of the harbor)it does not get used much and I always thought the fuel might be a little suspect causing the smoke. It seems like there has been a half a tank in there since I bought it. The marina always puts stabilizer in it during winter storage. I still think it might be a linkage issue but could it be the quality of the fuel? or maybe something with the injectors?
Thank you all for your input. I will discuss all these responses with my mechanic and let everyone know as things go along. I'm just not sure how long this will take to resolve. If it helps, this is a fresh water boat and has never seen salt water. The engine always starts immediately when the key is turned even after sitting all winter. The engine smokes some with a whitish color or grayish color smoke which increases with more throttle but the oil level is not affected. Because we use it for only short periods of time (in and out of the harbor)it does not get used much and I always thought the fuel might be a little suspect causing the smoke. It seems like there has been a half a tank in there since I bought it. The marina always puts stabilizer in it during winter storage. I still think it might be a linkage issue but could it be the quality of the fuel? or maybe something with the injectors?
Big Diesel
Reminds me of an exciting experience. While on duty at an Atlas E missile site in Wyoming the launch control center began shaking. Thr power production tech ran to the diesel room only to return in about a minute saying it is too late. Shortly thereafter we had one large shake and a loud noise. Parts of the diesel generator were inches into the concrete walls. Boring hours with frightening minutes
Reminds me of an exciting experience. While on duty at an Atlas E missile site in Wyoming the launch control center began shaking. Thr power production tech ran to the diesel room only to return in about a minute saying it is too late. Shortly thereafter we had one large shake and a loud noise. Parts of the diesel generator were inches into the concrete walls. Boring hours with frightening minutes
Fred - my thoughts on how it happens
Not being a diesel mechanic - this is my thought on how the runaway gets that way. Step 1. The injector normally injects a specific amount of fuel into the cylinder. Step 2. But, with just a little pressure on the fuel return line the fuel supplied is increased, even slightly, to the amount of fuel that is injected. Step 3. With the slightly additional fuel the result is an engine that runs slightly faster. Step 4. The now faster running engine causes the fuel pump to pump more fuel puting more pressure on the fuel in the return line thereby causing more pressure on the fuel going to the injector which then squirts more fuel into the cylinder. Return to step 2. Given the additional information Tomm supplied, that the boat is not a fairly new boat, I think it is likely the problem with with the return line. Rather than trying to clean the line I would just replace it. Another possibility, like in humans, a piece of plaque in a vein can break off and cause a stroke. In a diesel engine fuel return line this can happen too, only in this case you don't get a stroke (well.... maybe you could) but instead a runaway engine. Sidebar: In the "olden days", as my daughter calls them, we didn't have to worry about this problem. "Sailboats" didn't have engines. Sailboats that had inboard engines were commonly called "Auxiliaries". Non-sailboats with engines were called "Motorboats" where as today everybody calls them "Powerboats".
Not being a diesel mechanic - this is my thought on how the runaway gets that way. Step 1. The injector normally injects a specific amount of fuel into the cylinder. Step 2. But, with just a little pressure on the fuel return line the fuel supplied is increased, even slightly, to the amount of fuel that is injected. Step 3. With the slightly additional fuel the result is an engine that runs slightly faster. Step 4. The now faster running engine causes the fuel pump to pump more fuel puting more pressure on the fuel in the return line thereby causing more pressure on the fuel going to the injector which then squirts more fuel into the cylinder. Return to step 2. Given the additional information Tomm supplied, that the boat is not a fairly new boat, I think it is likely the problem with with the return line. Rather than trying to clean the line I would just replace it. Another possibility, like in humans, a piece of plaque in a vein can break off and cause a stroke. In a diesel engine fuel return line this can happen too, only in this case you don't get a stroke (well.... maybe you could) but instead a runaway engine. Sidebar: In the "olden days", as my daughter calls them, we didn't have to worry about this problem. "Sailboats" didn't have engines. Sailboats that had inboard engines were commonly called "Auxiliaries". Non-sailboats with engines were called "Motorboats" where as today everybody calls them "Powerboats".
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