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Thread: Compression

  1. #1

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    Compression

    I have air being forced out of the dipstick tube when I turn the engine by hand. It does the same when I try with the key. It acts like it has too much compression but I made sure valves were adjusted already. I can't check compression with my gauge because it won't spin enough.
    Model 31P777 0348E1 040426ZD

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  3. #2
    briggs's Avatar
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    Re: Compression

    your crank case vent could be blocked or not working properly....
    when all else fails ..Hit it with a hammer

    (I am here to help out where i can ..I will not be little u for asking a Question there is no such thing as a stupid question )

  4. #3

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    Re: Compression

    If you are turning the engine with the dipstick out you will get air being forced out of the engine when you turn the engine. It is caused by the piston displacing the air in the crankcase when it move down the cylinder bore. If the valves are adjusted properly then I would say that the compression release on the camshaft is broke and will required pulling the engine and replacing the camshaft.

    Currently doing that on the exact model that you have right now in the shop. The flyweight broke and was laying in the sump when the engine oil pan was removed.
    ILLINOIS ENGINE, BEECHER CITY, IL
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  5. #4

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    Thats what it seems to me too. But that is with the dipstick in. It hisses really loud when you try to crank the engine. Never had one do that before. Way too much compression and being forced out at the weakest point I guess.

  6. #5

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    How would you rule out everything to verify tearing into the engine. I have fixed those before but that was when I worked at a shop. I would diagnose and then the boss would verify. I guess I am just second guessing myself.

  7. #6

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    I had a guy tell me it was a bad starter cable. Because the solenoid was testing good and the starter was testing good but the voltage would drop when I connected to cable to the starter. But could that be because the compression is so high that the ignition system is trying too hard?

  8. #7

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    Re: Compression

    Could be blown head gasket between the cylinder and push rod cavity. that could also cause the excessive crankcase pressure.
    ILLINOIS ENGINE, BEECHER CITY, IL
    BRIGGS AND STRATTON MST (MASTER SERVICE TECHNICIAN)
    Sales and Service for Dolmar, Poulan, Briggs and Stratton, Kohler, Lauson(Tecumseh, LCT), Generac, Brute.
    Warranty service for MTD, Murray, Powerwasher, Karcher, Mcculloch, Earthwise, Earthquake, Yamaha engines, Hisun, American Sportsworks, Worx, Rockwell Tools, Great Lakes Technologies products(Wen, CZ), Efco, Snap-On pressure washers, and others.

  9. #8

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    So I definitely need to do a leak down test?
    Last edited by bwestbrook; 04-11-2012 at 03:52 PM.

  10. #9

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    How do y'all do your leakdown test. I know how to do one but I don't have the test kit. Just wondering some of the ways people have come up with.

  11. #10

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    Re: Compression

    I agree with IL bad head gasket. To do a cylinder leakage test I high recommend you borrow or get the proper tester.

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