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Discussion Starter #1
Been having some issues with my 2008 Sportsman 500 HO EFI. Back in the fall it kept stalling when coming to a stop. Finally got around to checking it out over the winter and determined that the rectifier was going bad. The voltage output jumped back and forth from battery voltage to 14 volts. Replaced it and everything seemed to be okay. Went to start it a couple weeks back and it was very hard to start. Checked the plug and the spark was pretty weak. Replaced the plug and that seamed to help. Went to start it today and it wouldn't start at all. Checked the spark and it's there, but very, very weak. Swapped out the coil with my 550 coil and it's still very weak. You almost can't see the spark. I fear I already know the answer, but figured I'd throw it out there. I guess the first thing i should do is check and clean all the connections just to be sure. Any other suggestions?
 

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Troubleshooting
No Spark, Weak or Intermittent Spark
• Spark plug gap incorrect
• Fouled spark plug
• Faulty spark plug cap or poor connection to high
tension lead
• Related wiring loose, disconnected, shorted or corroded
• Engine stop switch or ignition switch faulty
• ETC switch misadjusted or faulty
• Wire harness or connections wet, corroded or broken
• Poor ignition coil ground
• Incorrect wiring after repair (inspect color coding in
connectors, etc.)
• Faulty ignition coil windings (measure resistance of
primary and secondary)
• Sheared flywheel key
• Flywheel Loose or damaged
• Excessive crankshaft runout - should not exceed .0024”
• Faulty ECU
• Faulty CPS
• Low Battery
 

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Discussion Starter #3
Thanks. I have that manual. Most of those I've ruled out. I need to double check all the connections. I fear it's the ECU. However, I would expect the ECU to work or not work. The weak spark sort of points to a voltage drop somewhere.
 

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Discussion Starter #4
So I disconnected the ECU just to see if there was something going on with the connections. Everything's clean and I plugged it back in, but the fuel pump doesn't come on and it won't crank. Back to the book I guess.
 

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Discussion Starter #5
Figured it out. When I removed the CDI, it was enough to disturb the three solenoids right next to it. Some jiggling of wires and I could get the fuel pump to come on. Removed each and cleaned and greased the connections. Nice strong spark now.
 

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I meant to say three relays, not solenoids.
I know this is an older post, but did these solenoids look long and skinny almost like a fuse you couldn't check? having the same issue with my 2009 sportsman 400. Was running fine, the stopped. doesn't start any more, and has week spark
 

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Discussion Starter #8
No, these were three little, black cubes. Clearly they are relays. Directly under the headlight assembly is a panel that has to be removed to access. Under that panel is the CDI box (about 4" square). To the right of the CDI are the three relays.
 
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