Intermittant Loss of power...out of ideas! Please help!

Discussion in 'Mechanic and Repair' started by Mark Pappas, May 28, 2009.

  1. Mark Pappas

    Mark Pappas LawnSite Member
    Messages: 9

    We've got an Exmark Lazer Z HP mower with a Kawasaki 18hp motor that has been giving us a lot of trouble lately. We've put a lot of time and parts into it and have had little success. Description of the problem/ time line:

    Last summer: VERY rarely (as in maybe once every 2-3 hours) the mower would fall flat on it's face, and run very rough. It would miss and sputter, and would die if I turn the blades off. Sometimes it would come back after a few seconds, other times it required the mower to cool down and then it was fine again. It happened so rarely that it was basically impossible to troubleshoot.

    Replaced: Fuel Filter

    This spring: First startup, it cranked immediately and ran great until it warmed up. After that it runs like the throttle was pulled out, but doesn't miss at all. The engine is consistent in rpm, however it sits at a lower rpm then normal. It has a lot less power, and is barely usable. Then seemingly randomly, it will rev back up to normal rpm and run fine for a few minutes. If we let it cool down, it runs fine.

    What we've done so far: 2 new fuel filters, drained tanks/ new fuel 2 times, blown out all fuel lines, replaced fuel pump, plugs, voltage regulator, and ignition coils, removed and cleaned carb twice, cleaned fuel bowl a number of times, performed both hot and cold compression tests (< 10% variance from cylinder to cylinder)

    After replacing the voltage regulator, it began to do what it did last summer with missing and running rough every now and then, but it seemed to prolong the period before losing power (possibly coincidence?). Most recently we replaced the coils and after running it today, it made it MUCH longer then normal before losing power. When it started having problems, it was MUCH better, and only lasted a few seconds most of the time. However a new symptom popped up: When turning the key to off, the mower continued to run. I had to turn off the fuel to kill the engine.

    We're extremely frustrated at this point! Does anyone have any ideas? I can't help but think it's electrical related after most major changes coming from the voltage reg & coils combined with the new symptom of the mower not shutting off.

    Any help would be greatly appreciated! If you've made it this far, thanks for reading...
  2. DT Lawn Care

    DT Lawn Care LawnSite Senior Member
    Messages: 850

    Well the fact that it won't turn off brings the Ignition Switch to mind. Could be solenoid? but I don't think that it would even run. You might have some loose connections somewhere to correct your main problems, but if you've done all of that other crap, I would assume that you've checked all obvious locations.

    That is a very weird problem, considering all of the stuff that you've replaced.

    When I was reading the start, I was thinking ignition coils, but looks like you've got those covered. Could be the flywheel that actually works the magneto? The flywheel is what will power the coils. That is about the only other thing that I can think of.

    Good Luck
  3. Mark Pappas

    Mark Pappas LawnSite Member
    Messages: 9

    Thanks for the response...hadn't really considered the magneto thing, I will take a look at it and maybe consider a new part there depending on the price.

    We have looked at most of the obvious connections, but I'm wondering if maybe this could be a grounding issue, or just a lose connection that hasn't been found yet (or multiple). I should probably also note that fuel shutoff solenoid doesn't seem to be working properly, as it has been backfiring after shutoff. I'm tempted to make a new harness, because it almost seems like there could be a number of electrical connection problems. I'm just not convinced that that's what it is given the sequence of events.

    Any other ideas?
  4. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    I'd like to see some unit model AND serial numbers along with engine model AND spec numbers ?
  5. viper00085

    viper00085 LawnSite Member
    from NC/VA
    Messages: 237

    when it drops power, any type of smoke from the exhaust at all? When it drops power, can you pull the choke out 1/2 or more and it regains power?

    From your symptoms I dont think it is a carb/fuel supply issue, but if you see any type of black smoke from the exhaust it may be running rich or flooding everynow and then, or if the additonal choke helps it, it may be running lean on fuel for some reason.

    It def sounds electrical related. Grounds, ign switch and connections to start for sure with the engine not shutting down properly. I would get this situation fixed first, so it does not affect the rest of your troubleshooting, and who knows it may take care of all the issues.

    Also had one just like this earlier this year on a lazer hp. Customer complained of losing power, sometimes stalling, but very, very intermittent. It ended up being the seat delay module (safety module). Quick test on one side of the module is with the brake off and steering handles in, lift up off the seat. there should be a 3-5 second delay before the motor dies. If it shuts off right away, then the module is bad, if it does not shut off at all, check your grounds and wiring first. Now there are other tests on the module too, but they are more serial number specific.
  6. Mark Pappas

    Mark Pappas LawnSite Member
    Messages: 9

    Thanks for the tips viper, It doesn't smoke at all, and I've tried playing with the throttle/choke when it's rough and it doesn't seem to make a difference. My thought was that it was flooding also, but there doesn't seem to be any indication of that. One time I pulled the plugs after it was acting up and one had some unburnt fuel on it, but the other did not. I'm guessing that was because of the ignition system not working properly, not because of a fuel delivery issue.

    I'm pretty sure the motor will die the instant our seat goes up, so perhaps that's the problem. I always thought that it was supposed to be instantaneous for safety reasons. Are you sure there is supposed to be a delay?

    Sounds like I should probably be looking for a repair manual with some more detailed electrical info. Any suggestions as to where to pick on of them up? I will get the serial/ model #'s tomorrow later in the day.
  7. viper00085

    viper00085 LawnSite Member
    from NC/VA
    Messages: 237

    yep, there should def be a delay before it shuts off when the operator comes off the seat, a few seconds or so. Its there so on bumps, and with lighter operators,etc the unit does not constantly try to shut off and die.

    I dont believe exmark offers any serv amnuals, but they do offer good electrical troubleshooting guides for the units and components to us dealers thru there dealer websites. I dont know if they have the tech sheets avail to the public though. May want to call exmark tech help directly and see if they will give them to you or speak to your dealer.
  8. DT Lawn Care

    DT Lawn Care LawnSite Senior Member
    Messages: 850

    This must be only on an Exmark ZTR, because every other walk behind, riding mower, or ZTR I've used has no delay at all.
  9. Mark Pappas

    Mark Pappas LawnSite Member
    Messages: 9

    Checked the manual and it does mention that the seat saftey switch is a time delay system.

    But anyway, here are the #'s:

    Engine sticker read:

    CODE: FHV500V-A510
    E/NO FH500VA06289

    Model #: LHP4417KA
    S/N: 175793
  10. Ruben Rocha

    Ruben Rocha LawnSite Senior Member
    Messages: 577

    Not knowing hours on the machine.
    How long has it been since the valves have been adjusted?
    Should be like every 300-400 hours.

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