After a mower sits for some time and with the addition of damp conditions surface rust will collect on the coil prongs and flywheel.
I found this out several times when trying to start my mower. Just disassemble it and sand down to remove the rust as stated above and your mower should fire right off the 1st pull.

Hello,
I have the same problem. Tiller sat over the winter. Now no spark. I get a shock but apparently it's not strong enough to generate a spark. I cleaned the coil legs and magnet but it did not help. If I am getting a shock, can the coil still be "bad". Any suggestions? Thanks for your help

possible cracked spark plug

I don't get a spark between the plug wire and the chassis.

I had a problem with the same engine on a Toro Model 20458. No Spark. I disconnected the kill wire and it started right up after a few pulls. Does this indicate that there is an internal problem with the coil? Thanks very much for any assistance you may be able to provide.

If it starts after disconnecting the kill wire, I think that indicates that the kill wire is either grounded to the mower through a worn spot in the wire's insulation or the kill switch is stuck in the grounded position. Maybe bent or not moving with the kill-bar.

I'm here because I used rustyj14's earlier post in this thread to bring back from the dead a Craftsman mower that my neighbor had left out in the weeds for a couple years. Runs great now. Thanks rustyj14!!!

RustyJ14 you are the MAN! I had the same problem and for the life of me couldn't figure it out. The flywheel didn't look rusty but once I pulled the coil I saw the problem. Used a little steel wool on both and it now starts on 1 pull. THANK YOU!

Rusty Ya Ole Dog ! You should get the Member of the Month Award Bro ! Mucho Satisfied Customers Dude lol ! Cudo's .

NO SPARK!!!!!!!!!
Tried new magneto still NO SPARK kill wire is disconnected still NO SPARK Went to an old mower and removed mag and flywheel and installed them seperatly still NO SPARK. Normanally I'm not this stupid but this has me stumped. mag is installed correctly (kill wire on down side) All I can try yet is to install mag upside down and check. I have three differant mags and two flywheels and still NO SPARK. This is not cool.

i have the same problem. there's no spark. not even when i checked it with an electric tester without the ground wire. can anybody help me please???????????

oh forgot something else to say. i do feel when it shocks me but again no sparks..

To have spark on these you need 1) a good spark plug 2)a strong magnet in the flywheel 3) no ground on the small terminal @ the coil 4) a good coil.

sorry guys but i'm a little confused here.

when i removed the coil assembly, there's only a ground wire connected to the spade terminal of the coil, and the plug wire. when you say kill wire are you talking about that ground wire? if so are you saying to disconnect the ground wire and see i get spark?

when i used a multimeter to measure continuity between the plug wire and the ground terminal i get about 4.4 kilo ohm. is that normal. also, did you mean that there should be no continuity between the ground terminal and the coil legs?

the flywheel and the coil legs are a bit rusty which i'm going to clean it up. but mean time can you help me with the above questions. tia.

Yes, remove the ground wire from the spade on the coil. Modern coils, with ignition modules built into them, are tested with a coil tester. The simple step-up coils were tested with a multimeter, years ago.

My lawnmower is doing the same thing other's have meantioned. My question is this...Are all craftsmans products quaranteed for life ? I was under that impression & my reason for the purchase.

rustyj14 W/PA (My Page) on Thu, Jan 25, 07 at 14:35

rustyj14, your advise worked, but also had to tighten the cable, was stretched (to hold for it to start) getting a new cable and it will be as good as new.
Was worried, purchased it used for my hunny and then it didn't work. The X-husband came over and took care of it. Not all X's are bad, mine is pretty awsome with helping with repairs. Will be making a cover to avoid this in the future! Thanks again Rustyj14!!!

No spark on my 6.5 hp B&S engine. I tried cleaning the coil & flywheel. I replaced the coil, still no spark. Any other suggestions?

Ok, I have read this entire thread. I have two identical 6.75 b&s engines. One engine runs like new, the other has a no spark situation. First, I pulled suspect coil and cleaned with steel wool as well as the flywheel. Put it back together and still no spark. Next, I pulled suspect coil and known good coil off good engine and swapped them. Mower that ran still runs, mower with no spark situation still has no spark.....not the coil. (Gap was set,.020)Tried pulling kill wire....not kill wire. The magnet seems to be strong, but how strong should it be? Is it common for the magnet to go bad on a flywheel? This mower is only 5 years old.

Thanks for the feedback.

I guess what you are saying is that I should try a new flywheel. I will attempt to remove the flywheel. I notice that the 2 holes used to attach the puller to are not threaded? any suggestions?

I just today replaced the flywheel- to no avail. There is nothing else left to replace to get a spark. Anyone have any suggestions? I actually, for the first time, am at a loss for ideas to get spark for this engine.

Saugus, just get the 1/4" tap and just tapping two holes to make thread. then go pull it out and have fun!

ok I have seriously done everything in this thread to do. I went out bought a new coil and plug. Sanded all the rust off the magnet on the fly wheel. Set the coil gap correctly. Disconnected kill wire. I am still getting no spark. My father in law gave it to me because he could not get it to start. It is a Quality Pro farm and country. I would really like to get it working so I don't have to keep borrowing one. PLEASE HELP. Thanks

Changed my oil on a Yard Man lawnmower by tipping it on its side to drain oil. Now I have no spark to the plug. Anybody have any ideas what happened? I've had this mower for 11 years and it has started every time until now. Thanks for any help.

Thanks everybody! Had the same problem from leaving the mower out in the rain for a couple of weeks while the garage was full of stuff. Followed the instructions here and -- VIOLA! -- started right up.

For my mower, it consisted of:
1) remove two screws that hold the decorative top cover on
2) remove the screw that holds the oil filler tube in place (and then move it out of the way)
3) remove the 4 bolts that hold on the pull-cord mechanism.
4) remove the 2 screws that afix the magnet-thingy in place, then clean it thoroughly with steel wool till its shiny.
5) steel wool the rusty patches on the rotating core
6) reassemble.
I took of my gas tank, but not sure you need to.
Sorry for the non-technical terms.

I had no spark, pulled the kill wire, then had spark. Checked for rust, no help.
Removed diode bolt but left it conected to the wires and insulated the body of the diode from the engine. Motor ran fine.
Touched the diode body to the motor and it stopped.
Ordered new diode, cost a little over three bucks. Until it gets here I will be using the motor with the diode body insulated from the motor!

I did everything mentioned above and can only get the mower to run when the kill wire is disconnected but it idles up and down slighty an sounds like crap and wants to stall. My cable being too lose is
Grounding out the kill wire, that's one problem solved... Any suggestions on motor bogging? Air filter is removed and still does it...

I changed the oil and have a new plug installed. This all started while I was mowing, got about 1/2 yard done then the mower sounded like crap..... It's ran fine this whole summer till now.

One would assume that the carb would need to be serviced. You will want to know also that the brake is not dragging on the flywheel.

I fixed my non starting issue this way.

After replacing the spark plug and still not getting a spark I went about the sanding and cleaning of the magnetron/coil/magneto and flywheel advice, then reset the gap using a greeting card, I still got no spark.

I tried to start the mower and got nothing. I then tried to physically see a spark by grounding the (new) spark plug to the mower and looking for a spark, but saw no spark. Convinced that, because I couldn't see a spark, it must be the Magnetron, I called around and got a price on a new one. I was about to go and spend money on a new magnetron, but decided to first overhaul the rest of the system.

I removed the petrol tank and carb, as well as the pipe that runs from the carb to the spark plug. Using petrol I cleaned out the carb, which had a huge deposit of dirt inside it. I drained and flushed the petrol tank with new petrol till it was clean and shiny inside.

Using petrol, a toothbush and a rag, I degunked the throttle assembly and everything that was still on the mower.

I then made a new airfilter out of scotchbrite (dishwashing sponges), because the one I had on had been regularly cleaned, but not replaced in the ten years I've had the mower. I noticed the air intake (on the carb) was missing a gasket, so replaced this with a rubber washer I found. It needed stretching to fit, but just made it.

I then reassembled everything making sure the carb and air gaskets were well greased (with vaseline) and that the air filter was lightly oiled (using 15W-40 motor grade oil).

After cleaning and reassembly I lubed the throttle assembly and the throttle cable and sleeve with WD40 (otherwise known as Q20 or Tool-In-A-Can). Best way to do this is to spray the WD40 into the throttle cable sleeve at the top of the mower at the On/Off lever and keep shifting the lever on and off until it comes running out of the bottom of the throttle cable sleeve where it attaches to the throttle assembly under the carb.

After putting everything back together I primed the mower three times and pulled the cord. The mower started and then cut out. I primed two more times, pulled the cord and the mower ran like a dream.

Since I already had a new sparkplug in the shed, it cost me nothing (but time and head scratching) to fix the mower. I don't think I'd have accomplished this without all the previous advice given in this thread. So thanks for that.

This post is my way of paying back and can hopefully help someone else. And I think the message here, is that before spending money on what you think may be the problem, rather eliminate any other possible cause without spending money first. My mower motor is a Briggs and Stratton "Sprint" 375 4 stroke engine.

Ok, I've read this whole thing, and still no spark. Kill wire disconnected, 2 new magnetos, new plug clamped to frame to observe spark.Hooked up a KV meter to HV wire, and nada. No rust. What am I missing here??? I don't know how strong the magnets are supposed to be, but they sure pull the coil tight to them when I'm setting the gap. This is the set of 3 on one side of the flywheel. On the other side, there's a set of 5 which are much weaker. Is that how it's supposed to be?
Another (hopefully unrelated) question: what is the other coil used for or what does it do?
Anyone know of a free website where I can learn more about this stuff? Wasting the 2 magnetos just about kills me! Thanks.

Are you positive the plug is good? I had a "new" two-day old plug that I assumed was good but I'd run it in the mower a couple of times with the flywheel key sheared which was causing the engine to be slightly out of time and get hot and I guess it ruined the plug.
It wouldn't show spark at the end of the plug, but it would at the end of the cable. I took the plug from my tiller and it put it in and it fired first pull.
This after I'd replaced the flywheel key and coil.

This post was edited by super65 on Sat, Jul 13, 13 at 13:42

Thanks to everybody whom i have helped thru this column! Most of the things i have learned from past experiences, and with the help of others in this Forum, and several others. Occasionally, the help doesn't work, mainly because the help seekers can't follow instructions, or don't want to seem to be dumb. I was the same way, many years ago-when i got my first "junk" mower out of the garbage pick-up! But, i went on, picking many brains over the years. I worked it all up into a small mower repair shop, where i fixed many mowers. But:
As my dear wife is sick from too many cigarettes, known as Emphysema, and lung problems, i must curtail my work for a while. Added to that, i pinched a nerve in my back (as if i didn't have enough problems) And i am now limping around like an old Geezer! (Which, at the age of 88, soon to be 89) is probably just about appropriate. The wood leg didn't do it-just a bad step!
But, i'll keep checking in most every day.
One thing: Don't be too proud to ask for help! We're here to help you. Try the easy things first-some times they work great, and you won't have to buy an expensive ignition coil/ magneto. BT/DT: Rusty J

I did all the above and still got no spark but I did not disconnect the kill wire first(is that the middle one on back of magneto I will try that also my gap is only abot 6 to 10 thousandth what the old briggs wanted cleaned it still no spark

Here's a basic explanation of how the magneto ignition works and what can go wrong.
The magneto consists of 4 parts:
1) an iron bar magnet in the flywheel
2) a steel core in the shape of an "E"
3) a high-voltage winding on the E core, one end of which is grounded through a tab on the mounting screw and the other end goes to the spark plug connector.
4) a "kill" winding on the E core, one side of which is connected to somewhere in the middle of the HV coil and the other end goes to the kill switch (described later) via the spade lug and the green wire.

Here's a somewhat simplified explanation of how it works . As the flywheel spins and the magnets pass the E core, a magnetic "flux" (the magnetic equivalent of an electrical current) flows through the iron E core and the bar magnet. The bar magnet serves two roles here. The iron bar completes a magnetic circuit so that the flux can flow in a circle through the E core and the iron bar. The magnet also provides a source of the magnetic flux. As this magnetic flux rises in the E core, it induces a high voltage in the HV coil, firing the spark plug.

The engine won't start until the safety bar on the mower handle is engaged. Engaging the safety bar does two things, it mechanically releases a brake pad from contacting a shoe in the underside of the flywheel, and it opens a switch that otherwise grounds the kill coil. When the safety bar is released, the kill switch closes and grounds the kill coil through the green wire, which reduces the output of the HV coil below the voltage needed to fire the spark plug. Engaging the safety bar opens the circuit so that the HV coil can produce maximum voltage.

So what could go wrong that would prevent a spark? Check these things in order.
1) the kill switch could be shorted so that the green wire is always grounded even when the safety bar is engaged. This could easily be tested by disconnecting the green wire from the spade terminal at the magneto module and checking for continuity between the green wire and ground while moving the safety bar.
2) The green kill wire could be shorted to the engine somewhere. This can be tested visually or with a continuity checker or ohmmeter.
3) As described by rustyj14, heavy rust can interfere with the flow of magnetic flux through the bar magnet and E core. A similar problem occurs if the gap between the E core and the flywheel magnets is too large. You should be barely able to squeeze a standard business card between them.
4) Corrosion or oil could be preventing contact between the E core, the engine chassis, and the metal tab that connects to the HV coil. A little cleaning and sanding should clean this up. Also the screw should be reasonably tight.
5) The HV coil could have an internal break or short between windings. There's no easy way to determine this without special equipment, so if everything else checks out then you can assume this is the problem and the module needs to be replaced. There is no need to replace the flywheel.

One other thing that can go wrong is that the keyway that keeps the flywheel and crankshaft in alignment could have broken or bent due to the blade hitting a stump or big rock. This doesn't prevent the production of a spark, but the spark occurs at the wrong time relative to the position of the piston and valves, which will cause the engine to fail to fire or to kick back and yank the pull starter out of your hand when trying to start it. You can tell if this is the case by removing either the pull-starter or the metal engine cover and looking down from the top, verify that the slots in the shaft and flywheel are aligned with each other. If they are out of alignment you'll need to pull the flywheel and replace the keyway. The keyway is designed to break to prevent damage to the rest of the engine, but in rare cases the crankshaft can become twisted even though the keyway sheared off. If the crank is twisted, it's time to go shopping for a new mower.

About to lose my mind.... The advice in here is great. However, I have reset the gap on the coil, sanded the magnet and coil removing every trace of rust, unplugged the kill wire assembly, and nothing has worked. I can get voltage, if I push a 3" x 3/8" extension into the plug boot on my tiller I can touch the extension to my finger and my finger to the frame and feel the volts half-way up my bicep. If I draw the extension back even 1/16th of an inch, it won't jump from the extension to the frame. What am I missing?

tfr, that seems to be a strange way to check for spark. What are we working on? Heck, just take an old spark plug, ground the end and see if you have a quality spark. In my experience, most no start issues are fuel problems. A quick and easy test to see if what you are working on has spark and compression: Give a burst of carb spray in the carb venturi or spark plug hole (then replacing the plug) and give it a pull. If it doesn't try to run up- test further for spark then. A new thread w/ model numbers etc would work in your benefit.

Tomplum, it's a craftsman tiller with the Chinese engine. I'm using the extension to see if I can get the spark to jump to ground. I've tried several sparkplugs, and sprayed carb cleaner through the carb, I've tried starting fluid, I just can't get the spark to jump. The voltage is there, I'm just missing something on why it won't fire a plug.

Thank you rustyj14! Works like a top now.

Ok.

New Magneto
New plug
Gapped with heavy paper
no rust on flywheel
Kill wire disengaged
Carb rebullt top to bottom
starter fluid in cylinder and carb before replacing plug
Choke working
good compression
Timing OK
NO SPARK.

What's left?

This is a log splitter with a Briggs and Stratton 135212 engine, there has been no damage to the engine. It was running earlier this spring. Ran out of gas, and hasn't restarted since.

had same problem,tried all of the things listed here
did not start
son's little girl said put vasoline on it
makes everything better
i did all contact points
runs like new
crazy

Thanks to rusty14. My chipper wouldn't start and it was going to be 2+ weeks and $100-150 to get it looked at. I tore it down and looked at the coil and flywheel. The flywheel was a little rusty as was the coil but the coil also had some crud on it. I rubbed it down with solvent and sanded the coil pickups and the flywheel. It started on the 1st pull.

I have a no spark issue. It ran fine then shut off.
Once it cooled it started fine and ran until it got hot then shut down again.

It starts cold but wont run warm.
Eventually no spark at all unless the magneto (coil) is touching the flywheel magnet.

With a gap there is no spark but once I set the magneto touching the magnet there is a spark.
Does this mean the coil is bad?

Hi,
At my wits end here. I have a B&S 650 series engine that took a very light bump the other day to the motor and stopped working. Starter hard to pull and no spark however I can get it to run perfectly by levering the brake arm open or by disconnecting the kill wire.

The mower does not have a deadmans lever but does have the same brake apparatus as if it did (brake arm and kill wire).

My questions are:
- Is this brake arm/kill wire apparatus the problem?
- If so, what happened to make it a problem and how do I fix it?
- Is disconnecting the brake arm kill wire a reasonable fix given there is also a kill wire on the throttle that still works fine?

I really just don't understand how it could've ever run if the kill wire was always permanently grounded...

Thanks heaps
Greg

"I really just don't understand how it could've ever run if the kill wire was always permanently grounded..." It couldn't. I would assume that whatever held the brake arm in the run position is no longer there. Not really knowing why it has the mechanism or what this is on for that matter if it has no "deadman's control"... Did someone slap an engine on and slide a pin in the test hole of the arm/ bracket to disengage the brake? Does it have a seperate kill switch?

I Have an ancient Briggs horizontal shaft 2.5 horse engine. Has breaker points and a real carburetor with a float. probably been sitting for 40 years, and then found its way to a resale shop where I bought it as part of a David Bradley rotoSpader.cleaned a ton of gunk out of the carb and gas tank, fixed a hole in the float, Replaced the condenser and points, and it doesn't quite start. has a very weak spark, not enough to jump the spark plug gap, but occasionally visible if you are in a dark place and spin the motor pretty quickly while maintaining a very small gap to the end of the spark plug wire. The spark appears to be intermittent, not every time the engine goes around. Flywheel Gap is ten thousandths, spark plug gap is 30, and points are gapped at 20.

I fear my coil is bad, but don't really want to make that big of an investment in a $20 roto tiller. My question is, is it likely that the coil is malfunctioning because it is wet? I carelessly left it exposed, and it got some rain on it.

if so, is there any hope that it will get better if I leave it to dry out?

I pretty much cleaned and lubed everything, and I'm looking for some ideas.

I came across this thread by searching for the same answer a lot of others on here are seeking. After reading the entire page, I had to join to point out an observation in regards to rusyj14's comment that "Occasionally, the help doesn't work, mainly because the help seekers can't follow instructions"

But, the fact is, the seekers Are following instructions. No disrespect meant, as I see many have resolved their problem with your help. But the others that are still at square one have done as instructed. They have repeatedly stated those instructions back, as to what they had done, but with no fix. And as you also mentioned for them to do, they Are here asking for help, but it seems their posts are going unanswered.

From someone who at the age of 10, or younger, got his hands on his first lawn mower with instructions from his Dad to only tear it apart to see what was inside, with a Tecumseh that had sat out in the weather since who knows when, with a crankcase full of rain water, but defied his Dad and got it running to have it mow his grass for the next six or more years, I've been accustomed to getting things running.

But having already done what all others on here have suggested before finding this thread, I am leaning towards the flywheel magnets having somehow lost their strength. It is the only part not bought new to replace. I thought I had read somewhere else that someone was able to compare the strength between a good set of magnets and weak ones by use of a fish scale and how much it took to pull away from it, but I couldn't find it again. I'll be completely dumbfounded if a new correct flywheel does not solve my issue either, as I've mentioned, it is the only part I have not yet bought to have everything brand new with regards to the ignition system. If I had a shop nearby that could magnetize it, I would go that route, but it will be cheaper to purchase a new one than to invest in the shipping and shop time to have it done.

You may have something connected wrong, a short in the wiring harness, a rusty flywheel or magnet legs, the wrong setting of coil to flywheel gap, a rusty coil, a short in the grounding wire-lots of things can go wrong. I'd say--give it up and use it for a boat anchor, and go buy a new one. And, don't let it sit outside in rain, snow, winter weather, or heat, like in direct sunshine! Yeah-i know-"but, i let my car set out in the rain and snow--If you can't find anything wrong with that line--hire a man to mow yer grass, with his equipment, while you set back and quaff a brewski!

A word of advice: Don't let yer equipment set out in the weather!! Its NOT like yer car, or truck! Cover it with a tarp, keep it tuned up, and occasional new spark plug, and keep gas tank clean, watch for condensation, which puts water in the gasoline, even without yer help! Also, when ya turn the mower on its side to drain the oil, make sure the carb is on the high side. Most are designed that way. Condensation is caused by sunshine on a tin gas tank, and by the fuel. Good luck, folks. I hope you all have learned how to keep yer machines running correctly! And, i'm going to pick up my lady friend tomorrow, and go to lunch! Thanks to Houzz for allowing me to give advice to folks! I figger, at the age of 90 years, i have earned the right to drink my beer, chase wimmen, and relax! Rusty Jones

Your the man Rusty. I'm a newbee yesterday to this forum and collectively I have got my Dad's old mower started by disconnecting the kill wire from the coil and jumping the solenoid as when I turn the key it just clicks. It's s B&S 6.5hp Intek, all the safety switches seem fine, but once I start it I can't stop it unless I connect the coil kill wire back on the coil, lol. Any clues from anyone would be greatly received.

It is difficult to explain to somebody what you have to do to make it stop, or to restart it, thru this medium! Especially when the "newbie" has no experience. That said: Tie a length of clothes line to the spark plug wire, and yank it off the plug, and it will shut off. To restart it, push the spark plug connector back onto the plug, and pull the rope. It should start, if everything else is in order. Crude--but effective! Rusty Jones-the mower man. LOL!