# No Spark on 5 horse Brigg and Straton



## Sir Thomas (Dec 7, 2013)

I learned a quick lesson on an old 5 hp Brigg and Straton engine that I rebuilt sitting on a Tiller that was given to me. The rebuild was years ago and I have been using it. This year I tried to use it and it wouldn't start. I checked for spark and there was none. I did not have a multimeter then (I have one now) so I automatically assume it was the magneto coil and ordered a new one. I put it on and it still wouldn't start. Finally I pulled the flywheel, took the cover off where the resistor is and notice it was dirty. I completely removed everything, cleaned it and reassembled it. It started up and ran good for a while and then stopped. I pulled the flywheel off and checked the contacts on the resistor and noticed it had slipped because I didn't tighten it good enough. I light tightened it, checked for gap then tighten it down tight and it runs fine so before you order a new magneto coil, check the contacts on the resistor and get yourself a multimeter and check the coil.


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## paulr44 (Oct 14, 2008)

I've got one that doesn't make sense, perhaps it'll help someone out there.

OLD Tecumseh with points and condensor...after sitting for some time, such as a snowblower, it may not have spark. GROUND the spark plug lead, pull it over a half dozen times, and viola! Now it has spark. Probably something to do with the condensor, but even with all my electrical knowledge the answer eludes me...just doesn't make sense. DOESN'T work everytime, as points burn and condensors degrade but if you get something working in 2 minutes and it works for awhile, why not? I've had this senario play out and the engine may run all season without a hitch.


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## paulr44 (Oct 14, 2008)

Sir Thomas said:


> I learned a quick lesson on an old 5 hp Brigg and Straton engine that I rebuilt sitting on a Tiller that was given to me. The rebuild was years ago and I have been using it. This year I tried to use it and it wouldn't start. I checked for spark and there was none. I did not have a multimeter then (I have one now) so I automatically assume it was the magneto coil and ordered a new one. I put it on and it still wouldn't start. Finally I pulled the flywheel, took the cover off where the resistor is and notice it was dirty. I completely removed everything, cleaned it and reassembled it. It started up and ran good for a while and then stopped. I pulled the flywheel off and checked the contacts on the resistor and noticed it had slipped because I didn't tighten it good enough. I light tightened it, checked for gap then tighten it down tight and it runs fine so before you order a new magneto coil, check the contacts on the resistor and get yourself a multimeter and check the coil.


If your VOM is a good one, it can test the condensor (capacitor). It'll have to check farads. A typical point-ign. system condensor is 3 to 5 microfarads. You can also use the Ohm test on the point lead (you'd have to pull the flywheel and isolate the condensor from the points) to check how they're functioning, and if you have a dial indicator you can go through the spark plug hole with it and check timing. Old Tecumseh engines often fired at like 0.035" BTDC if memory serves me, but that what manuals with spec. charts are for.

I bought a Fluke 117 meter so I could check caps (capacitors) and set Hertz (you alter the RPM) on gensets.


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## Sir Thomas (Dec 7, 2013)

paulr44 said:


> I've got one that doesn't make sense, perhaps it'll help someone out there.
> 
> OLD Tecumseh with points and condensor...after sitting for some time, such as a snowblower, it may not have spark. GROUND the spark plug lead, pull it over a half dozen times, and viola! Now it has spark. Probably something to do with the condensor, but even with all my electrical knowledge the answer eludes me...just doesn't make sense. DOESN'T work everytime, as points burn and condensors degrade but if you get something working in 2 minutes and it works for awhile, why not? I've had this senario play out and the engine may run all season without a hitch.


Doesn't some condensors hold a charge and if it sits, you have to build the charge up again? I was told that if you use a motor all summer and then need to check the magneto, you should discharge it before putting a meter on it.


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## geogrubb (Jul 28, 2006)

Sir Thomas said:


> Doesn't some condensors hold a charge and if it sits, you have to build the charge up again? I was told that if you use a motor all summer and then need to check the magneto, you should discharge it before putting a meter on it.


Here is a link for how to test your points and condenser, pay no attention to the outboard reference. Have a good one. Geo
http://assets.fluke.com/appnotes/electricalpower/B0271b_u.pdf


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## hdman97 (May 25, 2006)

Geo That's a great article.
I used that one time on a outboard with a spark problem.
Good reference to keep on hand.


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## Sir Thomas (Dec 7, 2013)

*Using the Multimeter*

The question I had is what setting should I set the meter. Most I've seen just has one selection for the ohm but mine has 200, 2000, 20k, 200k, 2000k. If the magneto or ignition coil is free from the unit, you put the black to the metal connector in the spark plug cable and the other on the ground clip on the magneto/ignition coil correct?


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## dawgpile (Apr 28, 2008)

With respect to what range you should put your meter on, your picture shows it on the 20Kohm range. That should be sufficient for testing the secondary of the coil. When testing the primary of the coil, I'd use the 200ohm range(the lowest). Take a look at the aforementioned article on testing Magneto Ignitions posted by Geo. The first picture is a good representation of what you are dealing with. The secondary resistance will likely be 5K to 20K ohms while your primary will likely be 1 to 10 ohms.

I believe these condensers are in the 0.2 ufd (micro-farad) range. Regarding your question earlier about storing electricity, keep in mind the primary of the coil is in parallel with(or across) the capacitor and therefore when nothing is running, the cap(condenser) will discharge it's stored energy very quickly since the dc resistance of the primary is so low.

IMHO, if you don't have the ability to properly measure / test the capacitor, they are cheap enough to just replace. Using the ohms function of a meter and checking for some charging taking place is not definitive enough(at least for me!). Electrolytic caps such as this change in value over time, primarily due to heat. As such they may still exhibit "capacitor like" behavior but their actual capacitance can be off by an order of magnitude. [I repair electronic stuff for fun and profit and I can tell you from 40+ years of experience that the leading cause of failures in flat screen monitors and TVs as well as PC power supplies are electrolytic caps failing or changing value dramatically due to heat fatigue]

Bottom line, just replace it if you've already taken the time to break down the motor and pull the flywheel.

Finally, you refer to a resistor in your initial post. Keep in mind there is no resistor in the ignition circuit. Just the coil, points, points and condenser.

FWIW.... (nice article from the fluke archives geo!!!)

Merry Christmas!


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## paulr44 (Oct 14, 2008)

Yes, condensors are capacitors and can store energy and should always be discharged before testing. You do this by taking a screwdriver or an insulated jumper wire and bridging the terminals. An ign. system condensor usually doesn't have anything in it after unit shut-down, as the way to shut them down is by grounding the primary (to which the cond. is attached) side of the ignition which in effect is also draining the cond, and battery-based point ign. systems you cut the power to kill the eng., so the primary side discharges one last time (draining the cap too) on shut-down. An old CRT - TV cap. can store enough to kill you if the circumstances are right. I've read 10 milli-amps can kill you under the right (or more aptly, wrong) circumstances, by stopping your heart (which we know is electrically controlled). Any good test meter is self-protected by a fast-blow fuse, so no damage should occur if overloaded. Cheap meters though may fail if used wrong momentarily, such as trying to test voltage with the meter in the ohm's position.


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## Sir Thomas (Dec 7, 2013)

dawgpile said:


> With respect to what range you should put your meter on, your picture shows it on the 20Kohm range. That should be sufficient for testing the secondary of the coil. When testing the primary of the coil, I'd use the 200ohm range(the lowest). Take a look at the aforementioned article on testing Magneto Ignitions posted by Geo. The first picture is a good representation of what you are dealing with. The secondary resistance will likely be 5K to 20K ohms while your primary will likely be 1 to 10 ohms.
> 
> I believe these condensers are in the 0.2 ufd (micro-farad) range. Regarding your question earlier about storing electricity, keep in mind the primary of the coil is in parallel with(or across) the capacitor and therefore when nothing is running, the cap(condenser) will discharge it's stored energy very quickly since the dc resistance of the primary is so low.
> 
> ...


I get resistor and condenser crossed up in my mind. I figure since I was working on replacing the magneto I pulled the flywheel and cleaned the condenser/point area before I put the new magneto on. I fired it up and it ran and then died. I found I didn't tighten screw down enough and the condensor slipped down. I noticed the points mount had jumped out of place, apparently when the condensor slipped. Once I got the correct points gap and tighten everything down it runs fine.


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## hdman97 (May 25, 2006)

Dawgpile I have fixed a few flat screen TV and monitors also.
All were bad caps.I have a ESR meter which is able to test most caps without removing them.
I really think the engineers design them that way,as most fail after a year or so.
Cheap Caps are a ticking time bomb.


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## 30yearTech (Sep 14, 2006)

Just an FYI, unless the condenser has a dead short, it won't keep the ignition from sparking, it's there to extend the life of the contact points and minimize arcing. You can actually remove the condenser from this ignition set up and it will still work.


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## Sir Thomas (Dec 7, 2013)

30yearTech said:


> Just an FYI, unless the condenser has a dead short, it won't keep the ignition from sparking, it's there to extend the life of the contact points and minimize arcing. You can actually remove the condenser from this ignition set up and it will still work.


On a 4 cycle engine? What keeps the timing? So the condenser/points system is redundant.


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## 30yearTech (Sep 14, 2006)

The ignition timing on these engines is provided by the cam lobe that operates the points, and the flywheel key. A sheared key on this set up will result in loss of ignition spark. The condenser plays no part in the ignition timing. The system is certainly not redundant (outdated perhaps), without it, there would be no ignition spark. 

On a side note: Most Briggs and Stratton engines most use a condenser that is integral part of the contact points and cannot be replace separately. On most other engines the condenser is a separate component from the contact points.


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## Sir Thomas (Dec 7, 2013)

30yearTech said:


> The ignition timing on these engines is provided by the cam lobe that operates the points, and the flywheel key. A sheared key on this set up will result in loss of ignition spark. The condenser plays no part in the ignition timing. The system is certainly not redundant (outdated perhaps), without it, there would be no ignition spark.
> 
> On a side note: Most Briggs and Stratton engines most use a condenser that is integral part of the contact points and cannot be replace separately. On most other engines the condenser is a separate component from the contact points.


This is an older 5 horse horizontal shaft Brigg and Straton. The condensor and points were separate parts. The point is spring loaded on it's own mount resting against the cam lobe. The condensor is held in place by a screw and bracket. A continuity wire is attached to the spring on the condensor. The contact completes the circuit. Your comment about the sheared key reminded me that's why I pulled the flywheel itself. If figured that I'd clean whole thing while I got the flywheel off and when I put it all back together, I didn't tightened the bracket screw tight enough and the condensor slipped back. 

I have had no "official" schooling on 4 cycle engines but i have been tinkering around with and rebuilding them since I was 10 (I'm 64 now). Now that I'm retired I want to work on 4 cycle and 2 cycle engines as a hobby and make a little money while I'm at it to suppliment my retirement.


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## dawgpile (Apr 28, 2008)

Congratulations Sir Thomas for getting it up and running!

HDMan...I too use an ESR meter for incircuit testing and an HP Impedance Analyzer for out of circuit measurement. It's amazing that the engineers that design some of this stuff clearly have no clue how to properly size components like caps and resistors for power supply / hi heat duty!!

Happy New Year to all and may our small engines be kind to us!!! It's 5 deg here in NE Ohio as I write this!!!


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## usmcgrunt (Sep 16, 2007)

dawgpile said:


> Happy New Year to all and may our small engines be kind to us!!! It's 5 deg here in NE Ohio as I write this!!!


It is -17° here in Illinois and heading your way. Throw another log on the fire and Happy New Year to you.


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## Sir Thomas (Dec 7, 2013)

usmcgrunt said:


> It is -17° here in Illinois and heading your way. Throw another log on the fire and Happy New Year to you.


It's suppose to get down to 9 degree here in Charlotte, NC tonight


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