Hey everybody! As a mechanic I have plenty of EFI and electrical knowledge but I have never worked on an ATV before. So I'm not quite sure what if anything is/works differently. Before I even begin to list the problems I'm having let me say this baby has been rolled a few times and has had a fun yet hard life. The center display no longer works properly so I have no way of pulling codes. The display just flashes continuously, occasionally shows rpms and always says its empty. It also has had the complete wire harness replaced a year or so ago.
PROBLEMS:
-The Main fuse blows randomly. it will pop them every 10 min then will go months without doing it.
-Overheats randomly. Fan intermittently doesn't work. Will over heat with fan running.
-MAIN PROBLEM: We can ride through all kinds of mud and water with no issues every weekend then out of nowhere BAM! We shut her down and she wont start back up or she just dies and we may have only rode through a darn puddle. After letting it sit a bit she will start and idle but as soon as you give it throttle she dies. 9 times out of 10 after sitting over night she'll run like normal again.
I'm relatively certain its an electrical issue. From what I've read on here these have a lot of problems with the ECU. How can I figure out if this is my problem? I'm trying to figure out the link between all the issues. So far I have found no shorts or melted wires. The intermittence of these issues is making it difficult to pinpoint. If anyone can help me get closer to the main problem or knows where to find a full wiring diagram I'd be super appreciative!

 

Another member has similar problems and some of things I's check are bad places for shorts is the fuse block under the front panel. You can pull the block up and check for any of the wires that may have pulled out along with possible touching each other.Not a bad idea also if you have access to a fuel pressure gauge is to check that the fuel pump is ok. Should hold 39psi without dropping. Even things like a dirty throttle body from neglected air filters can cause problems on running. Plus don't overlook a common problem on these machines which is the thin wiring and connectors on the tps and tbap sensors that can cause erratic operation.Plus not a bad idea on using electrical grease on all the connectors if this happens with any kind of moisture. They along with the crank position sensor(this harness runs under the throttle body) can have small bare spots or internal wiring damage that can ground out spark or not make good contact. Same thing I mentioned on his post,plus here's a 5 buck manual that should help with the wiring schematic. 2008 Polaris Sportsman 500 EFI Service Manual PDF Download