How to diagnose and replace ignition coil with no spark on your mower.

what's up guys josh with metal in motion welcome back to another video so today we've got a very filthy looking craftsman push mower that has no spark getting to the spark plug the question is is it the ignition coil or is it the grounding circuit that grounds the ignition coil how do we know that's what i want to talk about today and that's what i want to show you guys so let's get started all right guys what we're looking at is a very filthy looking uh craftsman push mower that does not have any spark to the spark plug now the first thing we need to check how do i know it doesn't have spark to the spark plug use one of these spark plug testers this is a cheap five dollar six dollar spark plug tester from o'reilly's advanced auto any of those kind of places so this is just got one that lights up it's a light bulb inside they've got another one that is a thread style you can use that one as well that one is more for strength testing the coil this is more just telling you if you have fire and that's all we're interested in right now we're not worried about strength we just want to know do we have fire you're going to disconnect the spark plug wire plug it into the end of the spark plug wire and plug it onto your spark plug now you're gonna go up and squeeze the bale handle on the handlebar and pull the string over and either hang your head over to see this or have somebody look for you and i'm gonna do that i'm gonna hopefully you guys can see okay i'm gonna pull the rope and you guys look right in here it should light up orange if there's any spark okay so as you've seen there this did not light up so that tells us there's not any spark getting to the spark plug um you could replace the spark plug all you want but the the wire is not firing the plug the coil is not firing so this is what the coil looks like and it has a ground tab that sticks off the back of it the question is is it this wire this grounding circuit that is the problem or is it actually the ignition coil we need to separate those two to be able to figure out which one it is and so what you're going to have to do is figure out how to take the covers off your mower on this briggs stratton this is a really popular one two screws on top take that off you're gonna have three screws around the gas tank little 5 16 screws and then you're going to have two 3 8 on the front and two 3 8 on the rear i've already got those removed if you want to uh leave the dipstick attached i recommend you just clean right here where the dipstick goes into the engine block clean the dirt around it so when you take this off the dirt doesn't fall into your oil so we'll pull this cover off and just swing it out of the way and there is our ignition coil okay here is our ignition coil and if you look right here this is the whole brake system when you squeeze the handle up on your handlebar that moves this whole assembly you have a brake shoe that presses against the flywheel so that this slows down preferably within three seconds that's kind of the standard at the same time it's got a tab right here that when you release the handle that tab comes over and grounds out this wire this black wire runs down and under around town and connects to the ignition module i call it ignition module it's ignition coil connects to this coil right under here where my finger is so is it this problem or is it this problem the easiest way is to disconnect it right here from the coil so we're going to reach in underneath there's a plastic tab just like so there it is and it's now disconnected now there is nothing else other than some magnets which you can test right here magnets have plenty of strength to them so the magnets are not going to be the problem in 20 years of me doing this i've never had to replace the flywheel because of the magnets so the magnets really go bad say it was the uh the flywheel key was sheared that's still not going to affect the coil because the flywheel is still rotating and it's still generating spark in the coil it's just not incorrect time with the engine so the timing is out but it's still producing a spark so now that this is disconnected what we want to do is take the spark plug out you do not want to try this test with the spark plug in because this is the only way to shut the engine off and with this disconnected there is no way to shut the engine off so take the spark plug out and we're going to take our test light because we were connecting it to the spark plug we're just going to take a little jumper wire these are just super cheap wires you can get them at harbor freight or even at the parts store and i'm just going to ground this right out to the frame so all this is doing is just substituting the grounding it to the spark plug all right we're going to hold this up here i'll tell you what i'm going to do just to save from having to put all the covers and stuff back on i'm just going to spin this over with a drill but i am going to have to lock the handle down up on the handlebar because i have to release the brake to make it turn over easy so with the spark plug out there's no compression on the engine it should turn over very easy once that brake is removed and now we are going to see if it fires nothing should see a bright orange light right here and we do not have any spark at all that tells us that our coil is the problem not this ground wire so what we're going to do is take a 5 16 i do not advise tightening these with an impact like this tighten them by hand i'm just using them to remove it and to just take the slack out of the bolts pull off the old ignition module remember how the wiring uh how it was routed and i have another one and so we're going to plug up our ground wire because we're assuming obviously this would be a new one or a good used one and you need to set the proper they call it air gap for the coil and the air gap is the space between the coil and the flywheel obviously the flywheel is rotating around and so you have to have proper distance or it's going to rub so i'm just going to take some of the slack out of these bolts i still want the coil to be able to move back and forth like this and the specs for most briggs is anywhere from six thousandths of an inch to sixteen thousandths of an inch i'll tell you what you can do without getting too carried away in the details a feeler gauge is gonna be the most accurate way and i usually use that for my riding mowers and stuff but most push mowers if not all push mowers that i've done the business card has always worked slip a business card this business card is roughly 14 000 so it's on the bigger side slip it in and what we're going to do is rotate the flywheel until the magnets come around and the magnets are going to suck the coil up tight to the flywheel with the card in between so there it is get a little bit more centered on there there we go all right that's almost like spring loaded because the magnets are behind it and from there we're just going to hand tighten it up and not too tight these things strip out really easy just good and snug grab the card and rotate it out make sure there is no rubbing of the flywheel and we're ready to retest so we're going to hook our spark plug light back up i'm still leaving the spark plug out that's just the safest way to let's go ahead and route this back through the way it was [Applause] safest to leave that spark plug out so we don't have any accidental starting all right spinner over here i still i still have my uh bail handle up on the handlebar squeezed and that's leaving the brake off now that we have the ground wire hooked up that's actually disconnecting this ground wire just like it would if you're trying to start the machine but because the spark plug is removed it's not going to start there you go you can see we now have spark so that's it go ahead and let's put the covers back on put everything back on bolted up you're ready to go all right guys once you get all your covers buttoned back up don't forget to put your spark plug back in go ahead and gap it while you got it out 30 thousandths of an inch for these briggs and put it back in and test it out see if that works all right so just to recap if you disconnected the ground wire from the coil and the coil still didn't have fire you can check the magnets on the flywheel but 99 the coil is bad if you disconnected the ground uh wire from the coil and now the coil is firing the problem is with the ground wire or the brake assembly system somehow that brake is not releasing um and getting off of the ground wire it's still grounding it out somehow or the wire has has chafed against the engine somewhere and is shorting out against the engine which is actually grounding out the ignition coil so you need to check with that wire or the brake system so anyways i'm josh with metal in motion i hope that helped you guys again if there's something i forgot if there's an easier way of doing it let me know in the comments below i'll catch you guys next time

Channel: Metal In Motion Shop

Views: 37,468

Rating: 4.9072304 out of 5

Keywords:

Id: AKltkvId20M

Length: 9min 41sec (581 seconds)

Published: Thu Apr 29 2021