multihobbyguy 35 #1 Posted May 8, 2014 Hello. I have a 91 520 with a Onan. The tractor was running well then it just shut down. I checked and it lost it's spark. After it cooled off it would start and run for a few moments and then shut down again. Now it will only fire right when I quit cranking and fire then die. I first ran a jumper from the battery to the coil and it still didn't spark. I checked the coil per the instructions in the Onan manual. It passed and measured as it should. I replace the condenser and still no spark. When I check the voltage on the coil it is +12v in and out until I crank and then the negative drops to +10v. I would think that it should drop more than that but I really have no idea. I also did the ignition module check and I would rotate the engine by hand and I would get 1.5-2.3v - +12v the manual states that it should be 1-1.5v - +12v voltage but I only got under 1.5v once on the many revolutions that I tried. I am not real sure what the coil voltage on the negative side should be while cranking and I am not sure if the variance on ignition module is significant. If you have any other suggestions to try please let me know. Sorry the post seems to ramble.Thanks for reading, Chris. Share this post Link to post Share on other sites
Ed Kennell 35,612 #2 Posted May 8, 2014 Sounds like you need the expert "SOI". I'm sure he will check in soon. Have you checked the ignition switch ? Share this post Link to post Share on other sites
multihobbyguy 35 #3 Posted May 8, 2014 Sounds like you need the expert "SOI". I'm sure he will check in soon. Have you checked the ignition switch ? I did check out the switch. It seems to be ok. I took the plug off and cleaned it up some. I was surprised that it only had something hooked to 4 out of the 5 terminals. Doesn't look like there has ever been anything on the 5th terminal. I am not real sure on what to do next other than start swapping out parts. I will swap out the coil today and if that doesn't work I will pull the flywheel and replace the trigger. Share this post Link to post Share on other sites
boovuc 1,090 #4 Posted May 9, 2014 If you haven't already, take this thread to the "Electrical" Forum. It certainly sounds electrical in nature! Share this post Link to post Share on other sites
multihobbyguy 35 #5 Posted May 9, 2014 If you haven't already, take this thread to the "Electrical" Forum. It certainly sounds electrical in nature! Thanks for the suggestion. I had forgotten there was a separate area for electrical. Share this post Link to post Share on other sites
multihobbyguy 35 #6 Posted May 9, 2014 I tried the coil and it did not work, the test results were the same as the one that was in the tractor. Then I found a topic about 16hp Onan that SOI posted on that talked about diagnosing the problem and figured out with a couple of quick tests that it was most likely the trigger/ignition module. So I tore the flywheel off the extra Onan and stole the trigger from it and replaced it. Now it is running well. I have mowed about 1hr on it so far. I am surprised at how much fuel this thing drinks. It does seem to get get louder as I mow. When I first fire it up cold it seems to run smooth and quiet. After a few minutes the exhaust starts to get a little louder and then a little louder until it is almost uncomfortable then just levels out. I think it might have a little more shake when it warms up also. If you have a idea I would love to hear it. If it bothers me or makes me worry to much I will start another thread, Thanks, Chris. Share this post Link to post Share on other sites
boovuc 1,090 #7 Posted May 10, 2014 The P220 Onans are very thirsty motors. I wonder if your muffler is going south. The Onan mufflers are expensive too! Another cause could be your fuel mix may be off. Possible that after it warms up, it may be running too lean. This is something you will want to at least check out to make sure it isn't too lean. That equals heat as I know you also know and Onans are the last engine you want running hotter than they were designed to do. Next time you mow, after it starts to get louder and rougher running, give it a little choke and see if it straightens up under load. If it does, that carb will need a good cleaning. Share this post Link to post Share on other sites
multihobbyguy 35 #8 Posted May 10, 2014 The P220 Onans are very thirsty motors. I wonder if your muffler is going south. The Onan mufflers are expensive too! Another cause could be your fuel mix may be off. Possible that after it warms up, it may be running too lean. This is something you will want to at least check out to make sure it isn't too lean. That equals heat as I know you also know and Onans are the last engine you want running hotter than they were designed to do. Next time you mow, after it starts to get louder and rougher running, give it a little choke and see if it straightens up under load. If it does, that carb will need a good cleaning. I just found that muffler. I sure hope it is not going south. I will try what you said about the choke. I did clean the the carb when I was swapping engines and cleaning the tractor up. It really wasn't that dirty. I thought maybe it was running to rich on how much gas it used but what you say about running lean makes sense. Share this post Link to post Share on other sites
