TC10284 114 #1 Posted yesterday at 06:46 PM (edited) I have a 520H that is exhibiting symptoms of a bad ICM - will run fine until it gets hot and then start sputtering and only run briefly when under full choke. Once it cools off, it'll run fine for a bit again. OK, so I tried to replace the ICM which has P/N 166-0875. I've tried TWO aftermarket ICMs that supposedly match that part number specifically in the item description. BOTH are exhibiting this behavior. The behavior is that the timing is way off I believe. According to the P220g service manual under section 8-1, the voltage should go from 1-1.5v back to battery voltage when the flywheel timing mark is between one of the screws on the engine shroud. The behavior I see on the original module is that it goes to 1V around the starter area when I rotate the flywheel clockwise, back to battery voltage around the correct spot - between one of the two screws on the chafe screen. Well on the aftermarket replacement ICM, it dips voltage around the starter area when I rotate the flywheel clockwise and then immediately jumps back up to battery voltage right after the starter. And the aftermarket part in question (and I've tried two DIFFERENT aftermarket options at this point) are like these: https://a.co/d/04cf8GG9 Do I possibly have a rotor with weak magnets? Or is the aftermarket just too sensitive and/or garbage? Edited yesterday at 06:54 PM by TC10284 Share this post Link to post Share on other sites
lynnmor 8,827 #2 Posted yesterday at 07:51 PM I've only heard good reviews of the cheap modules but they are likely made by several manufacturers. Are you carefully following the direction of rotation in the manual? The older black rotors were troublesome, the newer gray ones are better. That silly shaped flywheel key may be a source of your problem, often they are damaged or installed backwards, the flywheel nut should be tightened to 55 ft. lbs. The fact that the choke makes a difference leads me to think it may be fuel related, usually when a module fails it shuts down till it cools. 2 Share this post Link to post Share on other sites
ri702bill 12,097 #3 Posted 21 hours ago 2 hours ago, lynnmor said: when a module fails it shuts down till it cools. I'll second that. 1 Share this post Link to post Share on other sites
TC10284 114 #4 Posted 20 hours ago 3 hours ago, lynnmor said: I've only heard good reviews of the cheap modules but they are likely made by several manufacturers. Are you carefully following the direction of rotation in the manual? The older black rotors were troublesome, the newer gray ones are better. That silly shaped flywheel key may be a source of your problem, often they are damaged or installed backwards, the flywheel nut should be tightened to 55 ft. lbs. The fact that the choke makes a difference leads me to think it may be fuel related, usually when a module fails it shuts down till it cools. That's about what I've experienced. When it happens, it sputters just a bit and dies totally. Sometimes I can limp it along enough to get back to the shed by dumping full Choke and then back down. I may do some more testing with cleaning the carb or a new carb. Anyway, I'd really like to know why the aftermarket ICMs don't seem to work for me. It's strange the behavior I'm seeing. Only thing I can figure is it doesn't like the rotor. My rotor is the original Onan gray ones that you see online. Not the black ones. Share this post Link to post Share on other sites
TC10284 114 #5 Posted 19 hours ago https://photos.app.goo.gl/UzBvLCQDZ6BFrmga8 Share this post Link to post Share on other sites
Bill D 2,859 #6 Posted 19 hours ago (edited) Any chance your 9 pin connector is damaged and causing power loss to the coil? Edited 7 hours ago by Bill D 1 Share this post Link to post Share on other sites
