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Thread: Fixing an old seized diesel?

  1. #1
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    Default Fixing an old seized diesel?

    I have an old Onan generator with a little single cylinder diesel engine. We call it the "whole boat vibration system." It stopped running towards the end of the season. It didn't stop while running, it just wouldn't turn over when I tried to crank it one day. Will not move. There is only a small bolt accessible to try to turn it with, so I am not yet convinced its totally seized.

    I was looking at replacing it, but wheweee, do marine diesel generators cost an arm and a leg. I was gonna buy a Honda portable, but before I go there I figure I ought to give a serious try to freeing this thing up.

    Anyone know whats the first step? Take out the injector and drop some oil in there? Hit it with a hammer?

  2. #2
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    Take out the injector and drop some oil in there? Hit it with a hammer?
    Try a mallet first.

  3. #3
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    Put some "liquid wrench" in and let it sit for a while.

    Then free by tapping sharply but gently with a wooden mallet.

    If you can't find liquid wrench, then WD-40 is likely similar.

    Alan

  4. #4
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    "it just wouldn't turn over when I tried to crank it one day. Will not move. There is only a small bolt accessible to try to turn it with, so I am not yet convinced its totally seized"
    Curious. Doesn't turn over with the starter-motor, or doesn't turn over with a wrench? Very different thing.... let me (us) know which it is, in order to avoid my offering you very little dollars <Grin!>
    If it turns over with wrench, but not with starter, then that is pretty easily fixed. Doesn't turn over with wrench (on crankshaft), then.... dang.
    Sometimes you've gotta leave the kibble out where the slow dogs can get some....
    ... Roy Blount, Jr.

  5. #5
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    Quote Originally Posted by PatCox
    I have an old Onan generator with a little single cylinder diesel engine. We call it the "whole boat vibration system." It stopped running towards the end of the season. It didn't stop while running, it just wouldn't turn over when I tried to crank it one day. Will not move. There is only a small bolt accessible to try to turn it with, so I am not yet convinced its totally seized.

    I was looking at replacing it, but wheweee, do marine diesel generators cost an arm and a leg. I was gonna buy a Honda portable, but before I go there I figure I ought to give a serious try to freeing this thing up.

    Anyone know whats the first step? Take out the injector and drop some oil in there? Hit it with a hammer?
    NO HAMMERS.... NO HAMMERS

    Did you hear that??? NO EF'n HAMMERS

    Remove the injector.... and drain the oil pan if possible.

    FILL the hole where the injector was with Marvel Mystery Oil. then FILL the oil fill with the same PLUG that fill... then remove a oil vapor hose or PCV Valve hose from the Overhead Valve lifter cover of it has one... FILL with more Marvel

    The idea is to FILL THE ENGINE with the Marvel Mystery Oil...

    Wait a week... maybe more.... then look for a place to turn the flywheel, it may be best to remove the Generator part from the Engine first.

    Here is an interesting read...
    http://www.ytmag.com/articles/artint40.htm

    You could use 1/2 Kerosene and 1/2 Marvel Mystery Oil
    Last edited by Gary E; 04-17-2006 at 04:18 PM.

  6. #6
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    An old farmer down the road from me favors pouring a few tablespoons of vinegar in the cylinder overnight IF it truely is the rings and piston that are siezed. Once it's turning, change the oil and make sure to get all the vinegar back out of the engine. And of course, try Marvel Mystery Oil first.

    Dan
    Master of The Ensign's Gig: a 7 1/2 foot flat bottom plywood skiff,
    and Prudence: Lightning #7896.

    Think Good Thoughts.
    Thoughts become words.
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    Actions become habits.
    Habits become character.
    Character becomes destiny.

  7. #7
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    Thanks all for your input, as there is pretty good consensus, I will give the MMM a try, I love the label on that product.

    To try to further explain the situation of the thing, it will not crank when I try the starter. I have tried to turn it by hand, and it would not turn. However, because the flywheel is inaccessible, I only had access to a little 9/16 bolt on the front of the crankshaft which I tried to turn with a small wrench. I remain hopeful that a large wrench on the crankshaft would be different.

    My best theory is that it took a little cooling water back into the cylinder from the exhaust manifold. I hope it happened while it was not running. I don't recall it having "stopped" while running. At least not in any noteworthy way, it would occasionally stall while running if I put a heavy load on it.

    Thanks again.

  8. #8
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    Before you do anything, remove the starter to expose the flywheel, test for movement of crankshaft by levering with a small pinch bar or big screwdriver against the ring gear. (never use a screwdriver as a pry bar! lol)

  9. #9
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    Pat,
    Canoeyawl has a good idea, and NEVER try to turn a diesel with that little bolt on the end of the crank, you will shear off that bolt then your in more trouble.

    Since you said it might have swalloed some water, the "the filler up with MMO" should allow you to turn it with the pry bar.

    If you are not real comfortable with this intire rebuild idea, look around the area where you live for a kid with a hotrod car. They know a lot about taking things apart and putting back together. If there's no one near you, find a local speed shop, plent of hotroders in those places.

  10. #10
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    "I love the label on that product."

    I think the smell is better than the looks of the lable.
    TALLY HO
    Ken

  11. #11

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    Does the engine have a compression release lever? Maybe try releasing that and cranking... do diesels ever vapor lock? Donno!

  12. #12
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    Default Update on the seized diesel generator.

    Following the advice here, I have started work on the poor old thing. First, I know a little more about it. Its a 30 cubic inch single cylinder 7 horsepower Onan. Its huge for its power output, and built like a tank. Its like someone just cut off one cylinder of my main engine. Seems relatively easy to work on, though.

    I took off the valve cover and determined that the valves seem to be operating properly and the compression release solenoid that activates on starting is also working.

    The crankcase oil is normal.

    I uncovered the flywheel. There is no starter motor, instead the dynamo-generator is reversed and starts the motor. I don't think there's a huge amount of torque from this arrangement, so that explains the compression release solenoid; the compression is released until the motor gets cranking some and then the flywheel will have enough momentum to start it.

    The flywheel has no teeth. It has two bolt holes in it, which I put bolts into, then put a crowbar between them to lever the wheel around. The bolts bend, the wheel doesn't move.

    I knocked it on the edge with a small sledge hammer a few times, like you would a stuck mayo jar, nothing.

    I took out the injector and filled the cylinder with Marvel Mystery oil.

    The piston seems to be low in the cylinder, it might be at bottom, which means I have little leverage from the crank to break it free.

    I am going to try to move it again tonight, when it will have had 24 hours to soak.

    Whats the next step, taking off the head?

  13. #13
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    So far you have done everything right. Try with the bar and if it goes, you may have just solved all the problems. If it does not go try movining it the other way, then back and forth intill it does turn. If it wont turn at all, then your right about taking off the head, and the pan so you can get a look at the lower end, worst case would be a bent or broken connecting rod.

  14. #14
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    Bent, I'd agree might sieze things up, if broken, the crankshaft should turn easier, but not around the whole 360 degrees.
    "Simple minds discuss people, Average minds discuss things, and Great minds discuss ideas".

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