Troy-Bilt/Briggs Won't Start/No Spark

Only in so much as reinsuring you that "Hall Effect Sensors" are not some sort of voodoo electronic magic.

Some repair manuals do have resistance readings, usually only for the secondary side ( coil leg to spark plug ) however these specifically apply to the specific meter made specifically for that brand of engine, not something bought from Harbour Freight.
But 1/2 witts read the numbers and type them into their presentations with no understanding about what they mean, or even worse will flip through a manual, see specks for a coil with a remote control unit and quote these with great authority.
Then there are special testing machines that read the actual pattern of the generated spark, its out put & duration.
They cost near $ 20,000 and usually need a known good coil for calibration so again, the industry standard is to replace with a known good one.
Easy for me I just grab a new one off the shelf hook it up, gap it too wide ( 0.020" ) and check for a spark. If I get one regap to 0.010" and give it back to the customer.
I use an inline spark tester ( red neon tube type ) and can tell from the intensity of the glow what is going on.
A good coil under a good magnet will make a strong spark when at the far end of its mounts ~ .150" to .250" or if using a 3 point tester, throw a 1/2" spark once the engine gets up to speed.
The wrong magneto module will not generate a spark or generate a weak spark.
Because the spark is made by a rotating magnet, it can be a + or a - spark depending which way the magnet is.
A module made for a N-S magnet rotation will not work properly on a flywheel with a S-N magnet rotation and then there are magnets that are mounted radially so they just have N or S pole pointing at the magneto module.

Because they are so fragile, most retailers will not take them back & I am the same.
I fit & test one for free, if the mower is supplied stripped ready for instalation but will not take a claimed DOA module back.
Anyone who will happily do that would be suspected of flogging off known iffy modules.

If you want to do your repair n the cheap then you are better off going to small ( Mar & Par ) repair shop and ask them for a 2nd hand coil.
make sure you have the full engine number, including the serial section with you because Briggs change specks , as of engine number ??????.

And I thought I was confused before. By "full engine number, including the serial section", do you mean that for my Briggs the serial number 12F802 0833 1 would be considered a full number?

NeedAFix said:

And I thought I was confused before. By "full engine number, including the serial section", do you mean that for my Briggs the serial number 12F802 0833 1 would be considered a full number?

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Yes it is not as easy as most would think which is a good reason to buy from some one who actually knows what they are selling and not an on line vendor who buys a pallet of part XYZ and then sells XYZ without the foggiest idea of what XYZ is or should work like.

That is the engine number .
It is the same for every engine troy-bilt bought in that order for that mower.
The serial number is the next bit 8 to 10 digits and in there is the year ( first 2 numbers ) followed by the day ( 1-365 ), followed by a code for the production line & the factory .so these are different one day to the next.

In spite of your extensive explanations I am still confused about ohm testing. Rather than warning of the hazards of resistance testing, Briggs recommends it. Copyright 2009 Briggs & Stratton. All rights reserved, in part: "Check the impedance (resistance) of the secondary circuit at room temperature. Hook an ohmmeter test lead to the spark plug terminal of the high-tension lead and another to the lamination stack (ground). Your resistance reading should range between 2,500 and 5,000 ohms." http://eu-en.myfaqcenter.com/Answer/?p_faqid=3805
There are a multitude of instructions and videos in regard to resistance testing Briggs coils, however, I am unable to find any sites that warn of the use of that process. Is there a reason why that information is not more common?

Going back to the previous post.
the module is both a generator and a transformer
On a car coil, 12 volts goes through the primary winding and in doing that the secondary windings convert the 12 V to 30,000 V which goes to the spark plug. Zap.
In a magneto coil, the magnet passing the primary winding generates (induces to be technically correct ) around 1500V in the primary which is connected to the chip.
The primary can not be tested without pulse generators.
The 1500V in the primary converts to 30,000V in the secondary coil and this is attached to the spark plug. Zap.
So you can do a simple Ohms test of the secondary which was in the previous reply.
But you can not repair or replace the secondary winding on the coil, just the same as you can not replace the secondary winding in your cars coil.
Both the primary & the secondary are together potted onto the laminations so as previously mentioned it is pointless.
On many of the coils/ modules. the spark plug lead is soldered onto the secondary so it can not be replaced without breaking the housing and even if it a screw in spark plug lead it is still potted in with a very high resistance resin.

If you are a Briggs technician doing a warranty service on a failed magneto module then Briggs want the readings which go on file & can be used to identify a bad or substandard batch of magneto module coils.
It also justifies the warranty credit of a new magneto coil for the dealers stock to replace the one they fitted to the customers mower.

To every one else it is pointless because if the secondary is faulty, the whole module is faulty and the module can not be repaired .
If the chip is burned out then the whole module is trash because it can not generate a spark and the module can not be repaired
If the primary windings are bad the whole module is trash because it can not generate a spark and the module can not be repaired.

Not knowing Troy-bilt walk behinds I assumed that this is a push mower with a pull start.
If it is an electric start then you need to check that the kill wire does not get battery voltage which will fry the chip.
If it is a pull start mower then the only repair you can do is to replace the module , or if the flywheel has poor magnetism, replace it as well.

So either the module you bought was dead in the box or you fitted it upside down.
Back in the previous post I mentioned polarity.
Some coils have legs that are the same size.
these can be installed upside down.
To the windings this is the same as reversing the magnet polarity and in that case the module will not work either.
Because of this the coils are usually marked This Side Up.
Generally the grounding tab will be underneath.

So it will be worthwile checking that you have fitted the module the right way round.
Usually fitting them upside down does not damage them.
We probably should have mentioned this earlier on but the coils are usually clearly marked.

NeedAFix said:

In spite of your extensive explanations I am still confused about ohm testing. Rather than warning of the hazards of resistance testing, Briggs recommends it. Copyright 2009 Briggs & Stratton. All rights reserved, in part: "Check the impedance (resistance) of the secondary circuit at room temperature. Hook an ohmmeter test lead to the spark plug terminal of the high-tension lead and another to the lamination stack (ground). Your resistance reading should range between 2,500 and 5,000 ohms." http://eu-en.myfaqcenter.com/Answer/?p_faqid=3805
There are a multitude of instructions and videos in regard to resistance testing Briggs coils, however, I am unable to find any sites that warn of the use of that process. Is there a reason why that information is not more common?

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I will jump in here and say something before I start talking LOL............

It looks like you are dead set on checking the coil for OHM impedance....... Like Bert said earlier don't rely on that, and don't rely on what Briggs have in their website.... There are a few meters you can use to test coils, BUT the cheap ones are not reliable for what you want.... A good FLUKE meter is what Briggs sells to their technicians thru their tool catalogs.......

There are only a few things for spark on a Briggs engine like you have.... The flywheel magnets, a good coil and a good grounding area where the coil bolts to.... No ground no spark...... A flat bastard file will do the trick to clean up the mounting posts........

It seems you have good magnets....... Coil is iffy if not bad ......... How are you checking for spark ????? In line tester that is a quality one or a Harbor Freight cheapo ????

The best tester is to grab the plug and have someone pull the rope....... LOL.....

I did read most of the other forum posts and I didn't see where you took the wire off of the coil itself to see if the ground wire was shorting against the engine somewhere........

Either you have a bad MOUNTING ground or a bad coil or a good coil and not seeing spark....... If so then you have a fuel issue.... Don't worry about a sheared flywheel key because it will still throw spark but at a different time for TDC....

Please keep away from OHM testing trying to solve your issue.... Get a good known coil and put it on your engine to try... A lot of those coils are used on many engines that size.. Example a coil from a 6.25 will fit a 6.5 and a 6.75....

Most lawn mower shops will keep good coils and sell them for half price.... I do sell good used parts to local people that can't afford new parts..

Let us know Mon Ami ~!~!

Okay, no more ohms talk. I'm getting to much information that is way to technical and questions are being asked that I have already addressed either here or in the other forum. The general consensus is still that the coil is the problem and the fix is to "try" another coil. "Get a good known coil", I thought I did that when I bought the new coils. I borrowed my Son's mower so I have cut the grass for the last time this season. If I figure out how to economically get a proper coil to "try" I'll tackle this problem again or, as someone suggested, I might just give up and look for a reasonably priced (the price of a OEM coil?) working used mower on craigslist. Should I resolve the no-spark issue I'll update this thread. I appreciate everyone's effort to assist.

NeedaFix - if u still have the ignition, email\call B&S. If they still have the same warranty as their old motors, the SS ignition is lifetime warranty. I don't know how they would handle it in that only replace to a dealer, want original receipt, or whatever...

As Boux indicated earlier, an electrically solid ground connection is often overlooked in this system.
Make sure that the towers to which the coils are mounted are clean, as well as the coil armature at this point,
and the underside of the washer head screws which secure the coil to the towers (engine frame.)
Also, make sure you set your coil-to-magnet gap per specs (about .010" if I am not mistaken.)
Good luck

Ronno6 said:

As Boux indicated earlier, an electrically solid ground connection is often overlooked in this system.
Make sure that the towers to which the coils are mounted are clean, as well as the coil armature at this point,
and the underside of the washer head screws which secure the coil to the towers (engine frame.)
Also, make sure you set your coil-to-magnet gap per specs (about .010" if I am not mistaken.)
Good luck

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Problem is Ronno he has been fed a pile of popular belief BS from some twerps on lawnsite that he can not get out of his head.
HE has been told about grounding and correct orientation of the coil ( although he has not confirmed orientation yet )
He bought cheapie coils off ebay and the vendor offered to replace or refund right up which to me means the vendor knows he is selling dubious coils because we know how difficult it is to return coils , even for licensed techs with trade accounts.
He also refuses to accept that a magneto coil either works or does not work.
He also refuses to understand that just because the magneto fits the space it might not be the correct one.

Illengine , Boudreaux & myself, three full time mower techs have all chimed in telling him the same thing but he would rather trust some shoved monkey on you tube.
Some people just can not be helped.
I don't think I could have explained things better without resorting to 20 pages of calculations and 50 diagrams.