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hit stump, mower died instantly

Discussion in 'Mechanic and Repair' started by brucec32, Apr 17, 2008.

  1. brucec32

    brucec32 LawnSite Platinum Member
    Messages: 4,403

    I went against my own good instincts and mowed an empty lot with sparse but waist tall winter wheat/rye sown for erosion purposes. Of course I "found" a hidden stump the hard way. The instant I hit it the engine died. Only the mower deck hit and hopped it, no physical damage to the clutch area. The mower will not restart and is DOA.

    Do any of our mechanical experts have an idea what the problem is? I suspect the blades suddenly stopping may have caused the clutch to burn out (though usually you'd expect a broken belt first) I've had bad clutches before but not ones that also killed the engine.

    It did cause the mower to leap up in front, but the driver presence interlock seems to be moving ok, not stuck in the off position.

    It's gotta be electrical I figure, which is so out of my league it's not even funny.

    Anything simple to check before I drag it to the dealer this weekend?

    Thank god for backup mowers, btw.
  2. brucec32

    brucec32 LawnSite Platinum Member
    Messages: 4,403

    Sorry, it's the Exmark lazer Z HP that's dead.
  3. jkason

    jkason LawnSite Senior Member
    Messages: 546

    If it caused the dec to jump, I would say it's one of two things:

    1 - Belt popped off the clutch and the clutch is fine. Put the belt back on and go.

    2 - Deck jumped, belt popped off and pulled wires out, causing clutch not to work.
    If the wires aren't too bad, you might be able to splice them back together.
    If not, the clutch is probably close to $300.00.
  4. brucec32

    brucec32 LawnSite Platinum Member
    Messages: 4,403

    The mower won't start or even turn over, so it can't be just the belt (been doing this 15 years, I thought of that one!. lol) But thanks anyway.

    Visually inspected it with it raised up, belts (deck, pto, pump drive) aren't even burned or burred up, much less off the spindle. If they'd locked up tight against the stump I'd assume some damage on them somewhere. Like I said, the machine died the instant I hit it. I'm not sure the blades even contacted the stump, which was only a couple inches high and old enough to be fairly soft. They're not damaged, at least, though they really wouldn't be on an old stump. Didn't see any major damage on the stump either. I think the front edge of the deck caught the stump and caused the machine to leap up a little. I've never had an engine kill that fast before.

    Some questions:

    1. I notice there's a mercury switch involved with the operator presence mechanism. How do I disable that to rule it out?

    2. Also, can one remove the blade engagement switch to rule it out? Do you have to jump it or what?

    3. Can shock from a hit damage any of the electricals?

    4. Is it even possible that if the clutch is burned out the mower won't even turn over?
  5. razor1

    razor1 LawnSite Bronze Member
    Messages: 1,985

    Check all fuses. Can you crank the engine by hand or w/the starter?
  6. razor1

    razor1 LawnSite Bronze Member
    Messages: 1,985

    How old is the electric clutch? I had the bearings burn up in one and it stopped the motor. Remove the clutch (usually 1 bolt) and try starting the eng.
  7. Tider6972

    Tider6972 LawnSite Senior Member
    from Alabama
    Messages: 649

    Bruce, sounds like the blow knocked the engine timing off. It 'may' have the sacrificial key like on push mower engines, I'm not sure. But if it does, that key is a soft metal and shears to protect the crankshaft. When it shears the timing is off. It would be under the flywheel. Pull the flywheel, it's the key which locates the flywheel to the crankshaft.

    Hope this is clear enough to understand; and I am guessing!
  8. LarryF

    LarryF LawnSite Bronze Member
    Messages: 1,181

    I have the same mower (except mine is a 52"), so naturally I'm interested. Almost sounds like a blown fuse, doesn't it? My parts manual has a schematic that shows a fuse for the ignition switch. Have you checked it? And how about the seat/tilt switch. Was the impact with you sitting on it enough to perhaps damage that?
  9. brucec32

    brucec32 LawnSite Platinum Member
    Messages: 4,403

    Yep, blow fuse. I'm an idiot. I had it in my head on the way home with it to check that first, but overthought it. I had no idea where the fuses were on the machine and when I spotted them when looking at other things it finally dawned on me.

    I guess the fuse did its job. That thing shut down in less than a second.

    Works fine now.

    Sorry for the wasted time.
  10. LarryF

    LarryF LawnSite Bronze Member
    Messages: 1,181

    Not wasted! Good information and now I know what to look for should it happen to me. Thanks for sharing.

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