Electrical Problem in Mower

Discussion in 'General Electronics Chat' started by tracecom, May 8, 2014.

  1. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    I have a Bush Hog CZ2149 zero turn mower with a Kawasaki 21hp engine; the mower has 240 hours on it accumulated over the last six years since I bought it new.

    Last year, I began to experience shut downs. While mowing along, the engine would suddenly quit as if the fuel had been shut off. After turning off the switch, the PTO, and setting the parking brake, the engine would restart normally, and continue to run sometimes for hours, and sometimes for only a few minutes.

    I replaced the fuel filter and the fuel pump. No improvement, but the shutdowns were infrequent enough that I put up with the problem for the rest of last year.

    This year, I mowed twice with it (about 6 hours, total) and had no problems. Then, on the third use, the problem became intolerable. The engine might run 15 minutes before shutting down and it might run less than a minute. Restart continued to be flawless.

    Now, I believe it must be an electrical problem; the wiring diagram is attached.

    I shorted out the seat switch: no change. I replaced the PTO switch: no change. I replaced the control lever switches: no change. I tested the parking brake switch: works properly.

    Something is apparently interrupting power or ground to the fuel solenoid on the carb just long enough for the solenoid to release. Then, of course, the safety switches keep it from retracting until the start up sequence begins again.

    Now, I am considering replacing the keyswitch, but it's just a blind shot.

    If someone has experience with a similar issue, I would love to hear about it. I have worked with the dealer and he's mystified, and Bush Hog tech support didn't help much.

    Thanks

    Moderators: If this doesn't belong here, move it to off-topic, please.
     
  2. #12

    Expert

    Nov 30, 2010
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    Irritating question, but how do you know it's about the fuel solenoid?
    Did you attach a meter to see if the fuel solenoid is losing signal?

    Personally, I'd suspect the magneto. Tiny wires, lots of vibration, crusty connections, bad reputation, etc.
     
  3. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    I don't know; I am just guessing. The mower is about 90 miles away at the farmette, and I didn't have a meter. I plan to check the voltage when I get back, but I think the loss of power could be so short as to be undetectable by my meter. I had planned on powering the fuel solenoid through a manual switch, and see if the problem persisted.

    The mower has always been garaged, and well maintained, and I haven't seen any rust anywhere, but I can look for it. I don't know how to test the magneto. Any guidance would be very welcome.

    Thanks.
     
  4. Alec_t

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    Sep 17, 2013
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    Have you checked
    1) the wire to the solenoid isn't fractured internally?
    2) the solenoid ground, if via chassis, isn't loose/corroded?
     
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  5. tracecom

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    I have checked both visually, and there is no obvious sign of corrosion. When I go back (with the proper wrenches,) I will take them both loose, clean the connection points, and reinstall them. Based on your question, I will also use my ohmmeter to check the continuity of the the ground wire from the solenoid to the frame.

    Thanks.
     
  6. #12

    Expert

    Nov 30, 2010
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    I think it's basically impossible to check a magneto for intermittent, unless maybe you can attach a meter and see if current pulses are still happening while the engine winds down to zero RPM during a stall.

    Edit: maybe you can tape a neon bulb to the spark wire with the leads not connected to anything?

    It's just, install one and see if it fails. The last one I bought was under $20.
     
  7. debe

    Well-Known Member

    Sep 21, 2010
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    Id be suspicious of the Ign coil as they quite often will break down when they warm up & will progressively get worse until they eventualy fail.
     
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  8. #12

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    That's what I meant when I said, "magneto".
     
  9. elec_mech

    Senior Member

    Nov 12, 2008
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    Admittedly knowing less about engines than most people here I'm sure, I'll ask some dumb questions.

    Does it have a battery? If yes, can you take it to an auto store or battery shop to get tested?

    Have you checked the sparkplug? Unlikely the culprit if starts and runs for a time, but who knows?

    Could the carburetor be clogged? Does fuel sit in the tank over the winter? Does the fuel have a stabilizer added? Personally I like Sea Foam. Also an unlikely culprit if the mower runs at all, but worth a thought.

    If there is a short in a wire somewhere, I wonder if you could remove the battery and use a Megger or Hipot tester (perhaps an auto store would have one?).

    Does the shut down occur while you're mowing? Would it be worth turning the mower on and allowing it to sit in place to see if it still cuts off in the same amount of time? May or may not help point to a problem related to vibration, which may or may not be helpful or conclusive. :rolleyes:
     
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  10. strantor

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    Oct 3, 2010
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    Pull your spark plug cap off, give it a gentle sideways squeeze with pliers. While you're at it, pull the plug and clean its spark gap surfaces with sand paper and flush it out with evaporative contact cleaner. Clean out the plug cap same way. If that doesn't fix it, investigate the coil/magneto and replace the spark plug wire. In my experiences, fuel loss isn't something I would describe as "instant;" rapid, but not instant. Usually some sputtering going on before shutdown. Spark loss issues however, are usually instant.

    All, "in my experience, " of course. Yours may differ.
     
  11. strantor

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    Oct 3, 2010
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    Plus if it were fuel loss it would be hard to get restarted as your carb would be empty.
     
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  12. #12

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    There was a good point in post#9. I have heard of crud in the fuel line that moves in and out of the clogging position. Bear of a problem to take all the fuel system apart. I guess that's why we're trying to find something electrical. :D
     
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  13. bwilliams60

    Active Member

    Nov 18, 2012
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    Your problem seems to be temperature related in which case I would be focusing on either the ignition coil or the ignitor. The flywheel you will find probably contains several magnets which provide the magnetic field for the ignition circuit. A coil is a coil and you can test it with an ohmmeter (static) and you should have around 0.6 ohms on the primary and 6-10,000 ohms on the secondary. It may be hard to catch as it cools off quickly but a heat gun or your wife's hair dryer :) may provide enough heat to catch it. Baring that, it could be the igniter and there are no real tests for that. I would call a dealer away from your location and ask what part he sells the most. They usually have common problems. Good luck and hope this helps. If your wife catches you with her hair dryer, I know nothing.:rolleyes:
     
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  14. tracecom

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    Apr 16, 2010
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    Thanks to all of you for your suggestions. I will print this thread and take it with me on my next trip, and will post my findings (and hopefully my success) when I return.
     
  15. wayneh

    Expert

    Sep 9, 2010
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    I second the suggestion to pull the spark plug, but I'd replace it with a new one until you get this resolved. It's never a bad idea to have a fresh plug anyway.

    A sparkplug on my boat engine quit firing once. There was absolutely zero visual indication that anything was wrong with the plug and it took me forever to diagnose the problem. Mine was not intermittent, but maybe it's possible to have intermittent plug failure?
     
  16. Stuntman

    Active Member

    Mar 28, 2011
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    I can't seem to look at a small engine without the magneto going bad, so naturally I will jump on the coil bandwagon.

    Fuel solenoids are always tricky because they will kill an engine fast like an electrical failure (remember, the solenoid is there to prevent afterfire so it is meant to kill fuel quick). However, the solenoid has to deal with many of the same durability issues as your magneto. It's basically a coil suspended in potting/varnish and has to heat and cool regularly (not only from engine heat, but self heating as well).

    In short, the fact that this is intermittent makes this a harder problem to solve.

    1. I would start with the easy stuff. If you have a spark tester (like this: http://www.amazon.com/Lisle-20610-Inline-Spark-Tester/dp/B0002STSC6) I would install in a fashion that allows you to view the indicator while running the motor. Start mower and run. When the motor starts to falter, see if you happen to catch if you are getting a spark as the engine spools down.

    2. The solenoid can be tested by removing the plunger from inside. I'm unsure how easy this is to do on your particular machine. See if this resolves the issue. The consequence to this is you may get some afterfire when you turn off the mower (assuming it doesn't turn itself off :D). To avoid this, turn the mower throttle down to its lowest setting for about a minute before shutting down the engine.
     
  17. alfacliff

    Well-Known Member

    Dec 13, 2013
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    I would not use a hipot or megger on the thing till I disconnected the voltage regulator. a lot of newer ones are solid state, and would not take kindly to a megger.
    has the gas been checked for water? my mower dies after a short time if the vent on the gas cap plugs up too.
     
  18. inwo

    Well-Known Member

    Nov 7, 2013
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    First determine if its ignition or fuel problem.

    If you have meter or tester. Check for power at carb solenoid. G/W After engine dies, but before reset.
    Or disconnect lead and connect power directly to carb solenoid. That's the only fuel supply part that will kill engine instantly.

    If engine still dies with fuel supply ok.

    Disconnect kill switch wire where it connects to ignition module/ coils. BK

    The engine # came up as a 2 cylinder.http://www.kawasaki.com/kengine/Eng...093-03_FR730V_FS730V_FX730V_English_eBook.pdf

    Engine will not die from other part failures suggested!
    Even if plug or coil was bad, it would still run. With the exception of one coil shorting out the kill wire of the other.

    If engine dies with kill switches disconnected at coils, and carb solenoid powered, at least you will learn what it's not.:D

    ps.
    For safety.
    Make provision to stop engine.
    Fuel shut off or kill switch.
     
    Last edited: May 9, 2014
  19. ErnieHorning

    Member

    Apr 17, 2014
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    One thing nobody’s mentioned is the gas cap. I had a push mower that exhibited this exact same problem. It turned out to be excess varnish in the cap that blocked air equalizing in the tank. The engine would run until it could no longer overcome the vacuum. The lower the fuel level is in the tank, the longer it will run.

    Just a thought but sometimes the obvious isn’t so obvious.
     
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  20. shortbus

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    Sep 30, 2009
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    Most of these two cylinder engines only have one coil, and work on the "waste spark" principle.
     
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