Jefflb 0 #1 Posted July 15, 2018 (edited) I have a 1990 520h with 20 Oman and has only 400 hours on it . As I cut grass the engine just shuts off but if I disengage mower blade real quick it will restart and backfire . I have changed the micro switches at the disengage handle but nothing . Anyone have an answer. I have also checked all grounds . One thing about it , it keeps all the dogs out of the yard while I mow ! It doesn’t matter if you are going downhill or up hill . I have even had it shut off while at idle and not be on the mower . It’s frustrating. Sometimes it does it 10 times during a cut or 3 times no real pattern. Edited July 15, 2018 by Jefflb Adding more information Share this post Link to post Share on other sites
buckrancher 2,668 #2 Posted July 15, 2018 have you checked the seat switch? 1 Share this post Link to post Share on other sites
WVHillbilly520H 10,369 #3 Posted July 15, 2018 Sounds like the ignition module/reluctor ring behind the flywheel, also I believe the early '90s models didn't have the "gasket" between it and the engine block so the heat seems to kill them faster doesn't matter on hours, had it happen on my anniversary model, Jeff. 1 Share this post Link to post Share on other sites
Jefflb 0 #4 Posted July 15, 2018 Thanks for the information. The seat switch was bypassed first thing to eliminate that but thanks for your input. I will check the last comments. Thanks for all that offer suggestions Share this post Link to post Share on other sites
N3PUY 1,031 #5 Posted July 15, 2018 Check the 9-pin connector. It hangs at the right rear of the motor. There could be a loose connection in it. With it running just wiggle it around. Share this post Link to post Share on other sites
Jefflb 0 #6 Posted July 15, 2018 Thanks I will do this.. Share this post Link to post Share on other sites
Jefflb 0 #7 Posted August 11, 2018 Well I replaced the seat switch and that didn’t fix it . Thought it would . I don’t understand why when i disengage or engage the mover deck it refires . Some times even when I try to crank it first time to start mowing it will crank over and over so I will wiggle the handle to engage mower it will crank right up . Then start mowing and it will cut off and I disengage mower it will restart right back up and sometimes backfire. I have replaced both micro switches at the mower engage handle . I wiggles all the wiring in the battery compartment with it running ( nothing ) also cleaned grounds to frame . Any more ideas . Share this post Link to post Share on other sites
N3PUY 1,031 #8 Posted August 11, 2018 Well, it's an ignition failure if it backfires out the muffler. Could be the ignition like Hillbilly says. But the easier thing to check is the power to the ignition. Take the 9-pin connector apart and with a very tiny screwdriver tighten up the female terminals. Do all of them. Just take the screwdriver in beside the terminal and bend it in a little. So it looks like a smaller, tighter fit. You don't need to remove the terminals from the connector. Just tighten them so the male terminal is a tight fit. Then go mow and let us know if that helped. If not then go to the ignition. 1 Share this post Link to post Share on other sites