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  1. #1

    94 SLT 750 No Spark

    I have been reading alot of the threads on here and they are very infomative. You guys really know your stuff so i joined to see if you could help. I have never worked on Polaris ski's (i have another brand). A friend of mine asked me to look at her 94 SLT 750 that was not getting any spark. It had been sitting for 2 years at her parents and ran fine when put away. I pulled the front plug and got very week intermittent spark and nothing on the other 2 cylinders. New NGK plugs and same result. I did all the ohm tests you guys have suggested in other threads and have listed the results below. The lanyard is in. All the grounds are attached and ohm out as good. I am a master electrician so I know how to do ohm tests. I disconnected the kill switch and still nothing. Switch ohmed out as good. I disconnect the temp sensors and nothing. They ohm out good as well. Box is grounded on both halves. Battery is very strong.

    Ohm Test results
    Alternator Coil Red/Purple to Yellow = .6 Ohms
    Trigger Coil white/yellow to black = 208 Ohms
    Pulser Coil Blue/Red to Red/white = 83.8 Ohms
    Exciter Coil Red/white to Green/red = 474 ohms

    Ignition Coils
    Primary Black to Black/white = .3 on all 3
    Secondary Black to Secondary Lead 3.3K Ohms on each
    Spark plug cap to lead inside = 5K approx on each

    My question is, could it be the flywheel or stator yet even though all the coils ohm out ok? Or is it the CDI box? Since it is not my ski, i would hate for them to spend that kind of money on a CDI box and that not be solution. I also do not want to pull the motor to check the flywheel and stator if it is the CDI. Does anyone have a known working CDI i could try to see if that is the issue? Or can I send the CDI to someone to try in there ski to check it. I am just south of Minneapolis, MN if anyone is in the area and would like to help me out.

    Thanks for all the help,
    Randy


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Welcome

    Did you confirm the stator coils are not shorting to ground?

    Tip: Even if you get it going with good spark, the rest of the machine still needs to be checked over.

    In particular the fuel system, and especially the carburetors. These engines really don't like even one carb to be gummed up, as this can cause lean piston burn down in just minutes when out on the water at speed. Rebuilding the carbs with genuine OEM kits is recommended.

  3. #3
    BlueFishCrisis's Avatar
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    I would be happy to try it out on one of my Skis. Would cost you about $12 total, $6 each way for USPS small flat rate box.

    PM me if you are interested.

  4. #4
    Well, BlueFish tested the CDI and it works fine. I checked the stator coils to ground and they were all good. Anyone got any ideas?

  5. #5
    Polarisitis loonatik's Avatar
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    Awhile back I read somewhere here about a case that stator was bad but ohm tested good. Hope it's not the case for you.
    Try disconnect black/yellow inside electric box see if it helps.

  6. #6
    How can i test the stator besides an ohm test?

    Quote Originally Posted by loonatik View Post
    Awhile back I read somewhere here about a case that stator was bad but ohm tested good. Hope it's not the case for you.
    Try disconnect black/yellow inside electric box see if it helps.

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by vos8869 View Post
    How can i test the stator besides an ohm test?

    Quote Originally Posted by loonatik View Post
    Awhile back I read somewhere here about a case that stator was bad but ohm tested good. Hope it's not the case for you.
    Try disconnect black/yellow inside electric box see if it helps.
    it is possible for a stator to pass the coil ohm checks (and Hall Effect tests) while the engine is not running, yet fail when subjected to engine vibration and heat.

  8. #8
    BlueFishCrisis's Avatar
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    Interesting thing happened while I was testing the CDI. I have learned in the past that the ignition system will let a random spark go intermittently with the lanyard removed ie motor killed. The motor will turn over, then catch for a quick second as it fires on the one spark then just keeps turning over. Typically when I test other CDIs i simply crack open the ebox, disconnect the host CDI, and plug in a harness that I fabricated. When I got this ski, most of the wire ends were cut. I was able to put new crimp on terminals on most, except the kill switch. In stead of tacking on a long enough wire, I simply soldered the kill switch lead to the black yellow on the CDI, with full functionality. I have been operating this way for 2 years without issue. Last night when I connected the harness, I needed to connect the black yellow to the kill switch. Since it wasn't landed on the circuit board, I pulled back the covering on the soldered connection and taped a pigtail into place, just for temporary use essentially landing the black/yellow from both the Host CDI and the kill switch on the circuit board. I then attached the harness black yellow to the circuit board as well. Tested the Vos CDI, no fire. I had another that I purchased and had not tested, so I swapped it in place. No fire. At this point I hadn't installed a spark tester, so decided to do that. This is when I noticed the intermittent spark that I usually get when the lanyard is not it. Curious, so I pulled the CDI black/yellow off the harness and immediately got spark and the motor started. Swapped in the Vos CDI, got spark and immediately started. Somehow with the HOST CDI still installed in the ski and connected to the Ground and the Black/Yellow was interfering with the kill function of the kill switch. Even checked to see if the black yellow was somehow being grounded out with the Host CDI still connected, and it wasn't.

    The point is, if you are getting intermittent spark, I would spend a bit more time looking at the kill switch configuration, making sure the black yellow is isolated from the ground, and that the kill switch operation of normally closed, open with lanyard installed, is indeed operating correctly.

    When you disconnected the kill switch, did you disconnect the CDI black yellow from the board, or just the switch from the board?

  9. #9
    I disconnected the switch from the board. I did not try disconnecting the CDI from the board. I will try that when i get the CDI back. Thank you very much for testing it.

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by BlueFishCrisis View Post
    ... This is when I noticed the intermittent spark that I usually get when the lanyard is not in. Curious, so I pulled the CDI black/yellow off the harness and immediately got spark and the motor started. Swapped in the Vos CDI, got spark and immediately started.

    Somehow with the HOST CDI still installed in the ski and connected to the Ground and the Black/Yellow was interfering with the kill function of the kill switch. Even checked to see if the black yellow was somehow being grounded out with the Host CDI still connected, and it wasn't. ...
    The CDI creates a voltage on Black/Yellow and senses the level of that voltage. When the Kill switch is grounding the Black Yellow then the CDI knows it should stop ignition. The Black/Yellow wire on the carburetor CDI is both voltage output and signal input.

    My expectation is that the CDI does not need the Black/Yellow to be fully grounded to kill spark, just dragged down to a voltage below some internal threshold. With two CDI both hooked up the Black/Yellow, the electronics of the 'non-powered CDI are still going to affect the voltage on Black Yellow. And apparently drags it down enough to kill spark.

    The Polaris CDI (all versions?) are designed so that even a momentary press of the Kill switch should entirely shut down the engine. Tap the Stop button and the engine stops running. That means that internally the CDI must recognize the Kill signal, then continue to suppress spark until the engine stops rotating.

    It would seem that what actually happens is that the CDI suppresses ignition for multiple seconds (I do not know exactly how long) regardless of the electrical state of the kill signal, then eventually 'times out' and again monitors the Kill wire. During this moment it apparently starts providing ignition/spark until it realizes that the Kill signal is still present. Hence your observation that you get the occasional spark while cranking with the kill signal is grounded.

    I could not say whether this occasional spark with lanyard out is consistent across all variations of these CDI.

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