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Uh, so I did the top end of a really old tigershark jetski\pwc. I've been having trouble torquing the head bolts right - I think the metal is fatigued. As such, head gaskets never lasted me more than a couple dozen hours. Long story, but not the point of this thread. I always thought preignition was just a scenario where fuel combusts early - can cause engine damage, sounds weird, etc. In this case it created quite a dangerous situation - engine ran away. I was trying to eject water from the engine after trailering the PWC. It started sucking air in from where the head gasket was cracked - it's connected to the side of the jetski to eject water. The engine started running away, max RPMs, no cooling. What the gently caress? Pulled the lanyard, did not stop. Pulled the plugs, did not stop. Thought for a second - what can cause that? Did I turn my spark plugs into glow plugs? It's so hot in the cyls that it's just self sustaining explosions? Ok, what can I do? Cut off the air? No way to block it. Ok, how can I stop fuel to the carb? Where is the shutoff? Oh....very...very close to the engine running away...not up front where it should be. Not burning the poo poo out of my arm or dying for this. Engine revved higher and higher. I detatched my car from the trailer, and pulled away, very worried about actual fire or explosions, carb sucking gas faster and faster, higher and higher RPMs with no governor. After much smoking, melting hoses, a bit of fire, the engine shuts down. I'm...pretty sure it's hosed forever, probably the bottom half too. Probably ran like that for 3 minutes. I haven't actually looked at the cyls yet. I knew what was going on, but didn't have a way to stop it. After the fact, I tried to do some research. Some people had luck pumping gas into the engine via the primer - try to create a very rich scenario. Is that the best thing to do\safest thing? More gas into something exploding? Maybe if you catch it early enough and recognize it for what it is? It took me a good 30 seconds to come to the conclusion what was actually going on. If I ever work on one of these again, I'm going to move the fuel shutoff closer to the front. I'm wondering if fogging oil aimed into the flame arrestor of the carb could also stall it out, might be worth carrying some. Apparently this has happened to some people on the water as well, the jetski flies off into the horizon. Horrifying. loving hell. What other options are there for stopping a runaway 2 stroke? Maybe stuffing my shirt into the exhaust...? Haha. SSH IT ZOMBIE fucked around with this message at 05:37 on Aug 7, 2017 |
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Aug 7, 2017 05:18
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That's both awesome and terrifying. No easy way to crimp the fuel feed?
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Aug 7, 2017 05:54
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Put in a brass shutoff valve mounted out away from the runaway death motor?
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Aug 7, 2017 07:54
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On nitro RC cars you just pinch the fuel line. most 2 stroke dirtbikes have a fuel shut-off valve, i would think your boatercycle would too.
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Aug 7, 2017 09:15
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Powershift posted:On nitro RC cars you just pinch the fuel line. most 2 stroke dirtbikes have a fuel shut-off valve, i would think your boatercycle would too. Yeah, it did. Right I'd have to wrap my arm around the engine to get to it. I didn't think of moving it.
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Aug 7, 2017 13:29
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Adiabatic posted:That's both awesome and terrifying. Hm, if I kept a pair of vice grips in the front, yeah, that'd work. It's relatively thick neoprene hose. One of the thoughts that ran through my head was pulling the gas feed out of the carb....but gas + something already on fire doesn't mix.
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Aug 7, 2017 13:30
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A CO2 fire extinguisher would have handled it, taking the oxygen out of the combustion triangle
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Aug 7, 2017 14:10
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Hell that may have been the only way, if oil was also getting into the combustion chamber through the head gasket.
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Aug 7, 2017 15:49
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Adiabatic posted:Hell that may have been the only way, if oil was also getting into the combustion chamber through the head gasket. Its a 2 stroke I second the vice grip idea. And get the head/block planed so the head gasket quits blowing.
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Aug 7, 2017 16:18
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Empty a fire extinguisher into the intake, as mentioned above. Best/safest way is to stop air from getting sucked in, but as I understand it the intake on those things is kind of strange.
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Aug 7, 2017 16:53
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rdb posted:Its a 2 stroke 
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Aug 7, 2017 17:21
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I probably would have done exactly what you did so don't feel too bad. No way I would risk injury or death for a loving jetski. Please post pics of the motor internals if you take it apart, should be interesting 
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Aug 7, 2017 17:44
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Applebees Appetizer posted:I probably would have done exactly what you did so don't feel too bad. No way I would risk injury or death for a loving jetski. Yeah, gonna do that. I'm also kinda curious. Gonna lift the engine out anyway to salvage parts. Will post pics when I do.
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Aug 7, 2017 20:42
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http://imgur.com/a/1S63I This honestly is boring and not anywhere near as bad as I thought it was going to be. The heat damage was localized to the top end, at this point I'll need to lift the engine out but the pistons even look intact. Rings are probably gone.
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Aug 8, 2017 02:13
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A buddy of mine had a farm truck overheat and diesel for an hour. It wasnt revving and it was a real piece of poo poo so we just let it go and drank some beer figuring that was that. After it died we replaced the coolant put gas in it and the drat thing still runs 8 years later. Its amazing the abuse some engines can take and be relatively fine. Also imo fire extingushers should be standard equipment on all cars. I saw a car park on grass and go up in seconds. We didn't even see the smoke before the flames had wrapped around the gas tank. A guy did have a fire extinguisher but in the minute he took to get there it was far too late. When we first saw flames i think it could have been saved. Hard to say but its a horrible feeling watching and knowing theres gently caress all you can do. Mount fire extingushers on everything imo.
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Aug 9, 2017 02:40
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One of my stepdad's employees (back when he owned a carpet cleaning company) went on a coke bender and took off in one of their vans all day. It took about as long for it to stop dieseling when he finally turned back up. Wasn't as much of a happy ending though, it didn't run again until the heads came off. 1984 Chevy G20 with a 305, if I remember right (this was around 1987 or so). Wasn't a happy ending for the employee either.
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Aug 9, 2017 04:59
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Breakfast Feud posted:Empty a fire extinguisher into the intake, as mentioned above. Best/safest way is to stop air from getting sucked in, but as I understand it the intake on those things is kind of strange. Not really applicable in this case, but amusing that the standard quick cure for a runaway diesel -- it usually happens during the first test-fire, while the air cleaner's still off -- is to put something solid like a 2x4 over the intake, and then throw a wet towel over it. Without the 2x4, it'll just eat the towel (or Tupperware lid) and keep on going.  https://www.youtube.com/watch?v=vbiNndfNNKI&t=119s
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Aug 21, 2017 05:12
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Bad Angus! Bad!
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I would plug or restrict the exhaust, most these two strokes can't rev for poo poo as soon as you knock out the effect from the expansion chamber. Also you won't cook the engine by leaning it out by cutting fuel.
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Aug 21, 2017 19:35
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Surely you can plug the intake. How much air can an engine really suck in through the gap created from a warped head/block? Enough to sustain high RPM? Though since it's a jet-ski, I'm guessing the intake is buried somewhere splash-proof.
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Aug 21, 2017 22:10
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Delivery McGee posted:Not really applicable in this case, but amusing that the standard quick cure for a runaway diesel -- it usually happens during the first test-fire, while the air cleaner's still off -- is to put something solid like a 2x4 over the intake, and then throw a wet towel over it. Without the 2x4, it'll just eat the towel (or Tupperware lid) and keep on going. I work with an older guy who used to drive old timey cement trucks in the backwoods of Canada when he was younger. He said that there was a lever under the dash to pull that would shut the air intake if/when the truck ran away.
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Aug 22, 2017 03:27
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Breakfast Feud posted:I work with an older guy who used to drive old timey cement trucks in the backwoods of Canada when he was younger. He said that there was a lever under the dash to pull that would shut the air intake if/when the truck ran away. All oilfield diesels are required to have a shut-off. on the pickups it's electric, on the larger trucks it's air, a lot of the older trucks it's a cable. http://www.rodadeaco.com/ I had to reach for it once and very nearly had to hit it when someone else parked their truck with the vent line pointing at the front of my truck while loading. The truck started chugging up, i realized what was happening and shut the truck off, and it kept going, i was going to flip the switch if it hit 1800 rpm, but it started dying back down and shut off. The last time i got it CVIPed, they hit the switch to test it, and then tried failing the truck because it wouldn't start when they tried taking it out of the shop without resetting it. There have been a lot of situations where there was enough hydrocarbon in the air and someone wasn't able to hit the switch and the truck ran away and blew up.
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Aug 22, 2017 08:54
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Powershift posted:All oilfield diesels are required to have a shut-off. on the pickups it's electric, on the larger trucks it's air, a lot of the older trucks it's a cable. http://www.rodadeaco.com/ Its caused two plant explosions that i know of in houston. Bp had let contractor park his truck at the base of a stack that vented. There was also the texas city explosion when a truck drove into a field that where a valve was leaking, a dip in the field made it a bowl of gas overnight.
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Aug 22, 2017 18:30
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DogonCrook posted:Its caused two plant explosions that i know of in houston. Bp had let contractor park his truck at the base of a stack that vented. There was also the texas city explosion when a truck drove into a field that where a valve was leaking, a dip in the field made it a bowl of gas overnight. I remember the BP one, we were in Spring and felt the boom.
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Aug 23, 2017 17:22
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