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no spark from 6.5 HP B&S engine

Posted by temperamental FL (My Page) on
Tue, Jan 23, 07 at 17:45

(push mower) Left my 6.5 HP Briggs & Stratton engine lawn mower outside in the wet weather. Won't start. NO spark what-so-ever. Removed cover, and couldn't find anything wet or damp. Could the windings have shorted out in the magneto. Is there an electronic switch somewhere that could have gone bad?
Thanks


Follow-Up Postings:

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RE: no spark from 6.5 HP B&S engine

Remove the stop wire from the coil. See if you get a spark.


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RE: no spark from 6.5 HP B&S engine

In all probability, the rain dousing has caused rust to form on the magnetic strips in the flywheel, and on the legs of the coil/magneto! You will have to remove the engine cowling-the part that covers the flywheel and cylinder. 4-1/4 inch bolts (7 sixteenth heads) hold it on. Some times the bolts might be larger. Any way, take those bolts out, unclip any wires from the cover, and lift it off. Remove the coil,-held on usually by 2-1/4 inch head, bolts.
Using sandpaper, sand the legs of the coil until they shine, then sand the strips on the flywheel.
To install the coil and to set the proper gap:
Cut a 1 1/2 inch by 7 inch strip from a greeting card.
Set the coil back on, with the magnets on the flywheel turned away from where the coil sits. Install the bolts loosely., thru the coil, into the posts. Then tighten the bolts snugly enough to hold the coil away from the magnets. Place the strip of greeting card between the coil legs and the flywheel. Turn the flywheel until the coil legs are opposite the magnets, and the card strip is in place. Then loosen the coil bolts, the coil will slip in against the the card strip, then tighten the bolts snugly, so no movement is possible, but don't break them off, as that will cook yer goose! Then turn the flywheel and the card strip will come out, and the coil leg gap will be correct. Reinstall the flywheel cover, and it should start up!


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RE: no spark from 6.5 HP B&S engine

Well, the first thing I got was a Briggs & Stratton repair manual-no help whatsoever. But it did tell me to check the "stop wire" like Rosemarrow suggested. Didn't help.

Next I did what Rustyj14 suggested. Success. In fact, it runs better than when it was new. Started on the first pull. Plus Rustyj14 gave great step by step instructions that I followed to the letter. HE should be writting the repair manuals. The Briggs & Stratton manual didn't even mention that rust could be a problem when there wasn't a spark.

Thanks a lot for the help. You saved me a repair bill, and I learned a valuable lesson about leaving my mower in the rain.

Thanks again


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RE: no spark from 6.5 HP B&S engine

Say, Temperamental, thanks for the vote of confidence! We all try to help folks whenever we can! I run into that problem when i find old mowers that have been sitting outside. The owner tries to start it, but with no success, he sets it out beside the garbage can, and i come along on garbage night, pick it up, take it home, clean the flywheel and carburetor, sell it and make spending money!


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RE: no spark from 6.5 HP B&S engine

Have similar problem, no spark, but following rustyj14's instructions yielded no results.

I'm thinking there is a short in the coil because there is continuity from the cut-off wire to the legs when the coil is removed and isolated from from the engine. To me, this means the coil is grounded to the engine when mounted on the posts, just as it would be when the cut off wire is grounded.

Does anybody understand what I am saying, and is this my problem ?


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RE: no spark from 6.5 HP B&S engine

Not really sure if it is the problem or not.
Keep in mind continuity from coil legs to block mounting posts is for completion of electrical circuit, required for any electrical circuit to exist. Grounding the internals with the kill wire is something different as it is short circuiting the deal as it is shorting or grounding the supply from the coil to the plug. The coil legs are simply allowing the plug to return juice to the coil to complete the circuit.

Showing continuity from the kill terminal to coil legs is the same as to the block and is completing circuit as well, just not the operating circuit.

If you have good continuity from coil legs to block and have the kill wire disconnected and get no spark, your coil is dead. Providing this is not a old point ignition unit.


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RE: no spark from 6.5 HP B&S engine

To Nevada Walrus: With the kill wire disconnected from the coil, and the entire assembly (coil and spark plug wire) separated from the engine, I get continuity from the kill wire spade connector, to the coil legs. I think that confirms your diagnosis that the coil is bad. Will try a different coil.


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RE: no spark from 6.5 HP B&S engine

New coil did the trick. Runs fine now


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RE: no spark from 6.5 HP B&S engine

Just want to say thanks to RustyJ14 for giving me the insight to the hard starting problem i had. A little polishing and it starts on the first pull. Just like it was new again. Thanks.


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RE: no spark from 6.5 HP B&S engine

is there any way to check out if a coil is bad? with my electricity tester?


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RE: no spark from 6.5 HP B&S engine

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.


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RE: no spark from 6.5 HP B&S engine

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


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RE: no spark from 6.5 HP B&S engine

possible cracked spark plug


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RE: no spark from 6.5 HP B&S engine

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


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RE: no spark from 6.5 HP B&S engine

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.


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RE: no spark from 6.5 HP B&S engine

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!!!


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RE: no spark from 6.5 HP B&S engine

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!


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RE: no spark from 6.5 HP B&S engine

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


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RE: no spark from 6.5 HP B&S engine

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.


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RE: no spark from 6.5 HP B&S engine

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???????????


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RE: no spark from 6.5 HP B&S engine

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


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RE: no spark from 6.5 HP B&S engine

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.


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RE: no spark from 6.5 HP B&S engine

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.


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RE: no spark from 6.5 HP B&S engine

  • Posted by baymee LehighValleyPA (My Page) on
    Mon, Jun 14, 10 at 6:29

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.


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RE: no spark from 6.5 HP B&S engine

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.


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RE: no spark from 6.5 HP B&S engine

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!!!


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RE: no spark from 6.5 HP B&S engine

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?


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RE: no spark from 6.5 HP B&S engine

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.


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RE: no spark from 6.5 HP B&S engine

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?


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RE: no spark from 6.5 HP B&S engine

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.


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RE: no spark from 6.5 HP B&S engine

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


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RE: no spark from 6.5 HP B&S engine

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


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RE: no spark from 6.5 HP B&S engine

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.


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RE: no spark from 6.5 HP B&S engine

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.


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RE: no spark from 6.5 HP B&S engine

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!


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RE: no spark from 6.5 HP B&S engine

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.


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RE: no spark from 6.5 HP B&S engine

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.


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Fixed non starting issue

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.


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RE: no spark from 6.5 HP B&S 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.


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RE: no spark from 6.5 HP B&S engine

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


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RE: no spark from 6.5 HP B&S engine

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


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RE: no spark from 6.5 HP B&S engine

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


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RE: no spark from 6.5 HP B&S engine

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.


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RE: no spark from 6.5 HP B&S engine

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?


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RE: no spark from 6.5 HP B&S engine

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.


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RE: no spark from 6.5 HP B&S engine

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.


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RE: no spark from 6.5 HP B&S engine

Thank you rustyj14! Works like a top now.


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