I am at a serious loss. My 2011 Sportman 800 EFI will not start. It cranks, but won't fire. I have replaced plugs and checked them for spark and get good spark. I have pulled the injectors and they are spitting out plenty of gas. I have tested the TPS sensor and get the proper voltage readings. Checked the battery voltage, all fine. Checked all the fuses and are all good. Occasionally after several cranks and giving it throttle I will get a pop, like a back fire but out of the airbox, not the exhaust. I also have checked the compression and its fine.

Thanks to anyone with ideas.

 

Welcome to the forum! About the only thing I can tell you is to pull the ecu connector,clean, fill with electrical grease, plus could be the T-bap harness problem that almost all eventually had (2875542 kit # OR read the "sticky" at the top of this section on efi problems)Only so much you can physically check out on efi atvs now without hooking up to a dealers Digital Wrench software to pinpoint the problem. The t-bap harness was the most common problem,but the tps harness could have a short in the small wiring also. Another thing is to check the crank sensor harness and connector that routes under the throttle body for any bare wires that might be touching the engine. Have had a few do this causing backfiring,etc. Check the small t-bap and tps sensor wiring carefully for any soft spots ,doesn't always have to have a bare spot. Could have internal breakage along with wiring pulling slightly out of connectors also from vibration. OPT

 

Thanks for the quick response. Loved my old carbureted Polaris. I have already had a no start that turned out to be the 20A main fuse vibrating loose/getting packed with dirt, Had the TPS sensor wire break and had to do field repair on that. I cleaned the ECU connector and greased, so I will give the TBAP and Crank Positioning sensors and wiring a look tonight.

Thanks again for the quick response.

 

Just to give a heads up, after checking every wire, sensor, etc. I took it into polaris and had them put it on diagnostics only to find out it was something so obvious I never thought to check it.....no compression. So get the joy of rebuilding the top end. Bike is only 12 months old but thats what happens when your careless and get crap in the engine.

 

Were you using the correct weight oil,swamped engine,etc?? Bummer
OPT

 

even dumber, I tipped it in a soupy mud hole. Once the snorkel went under it sucked mud into air box. Mud was thick enough that it didn't completely drain out of the airbox, but liquid enough that it could flow. I removed K&N to clean it and didn't put it back on before pulling it out of hole (backwards) and in doing so must have gotten mud inside. I got it cleaned up and it fired right up and rode for the rest of the day, so i assumed everything was fine. Thats the only thing I can think that had to happen as it would have been the only opportunity to get dirt in the engine.

 

Throttle body is just an open hole with a butterfly valve,easy to suck in mud and dirt. Sorry for the problems. OPT

 

OPT, so i got the new pistons etc installed and it ran great the first day out. The next morning it started having a major rattling noise in the engine. I took off the valve cover gasket and 3 of the 4 rocker arms I can move freeley. The is between an 1/8th and a 1/4 inch gap in between the rocker and valve or rocker and rod depending on which way you move it. The rocker arms are tightened completely dawn to specs, so what can be causing the free play?

 

This normal because of the hydraulic lifters! As long as the rocker arm bolts are tight you will have a little play on some rocker arms as the engine turns over. This the main reason people ask why there is a tapping noise coming from the top end on the 600,700 and 800 engines. OPT

 

07 sportman 800 had diagnostic test done replace tmap hardness also starter and Bendix plugs fuel injectors fuel fuel new gas new battery.Started right up run about 20 sec. died hasn't started since been trying for two days.Turns over great getting fuel and spark. Please HELP