sometimes spark on briggs

[eljefino]

1YPE-191707-21G1-01-8C051409

8 HP briggs electric start on a 1986-ish toro riding mower.

sometimes have spark.

have read that anything past 1982 has electronic ignition.

otherwise I would be pulling the flywheel to check the points.

here's my q, then:

Is the coil, riding near the flywheel, the only ignition bit on this whole engine? (and the only thing to replace?) It seems to have the "ground this black wire to stop" magneto action; while the battery charging is handled by another stator deeper within the motor.

The black wire disappears under an engine cover before reappearing on the other side; I assume if I had points ignition it would be wired into that.

 

[eljefino]

have the coil off, the kill wire does not stop anywhere inside the engine. am assuming electronic ignition but they are good at hiding the "brains"!

trying to find a part #, as far as I've gotten is an "1886" stamped in the resin-- maybe it was made the 18th week of 1986?

there is a tiny briggs logo, and C and L letters near various sides of the coil. 2.5" spacing between bolt holes.

 

[ChrisJH]

There is a decent Briggs manual floating around on the net (freely downloadable) that explains the ignition systems.

The kill wire is a switched ground, connected to the ignition key. When that wire is grounded, it prevents spark from the ignition coil. Its possible yours is shorting to ground somehow.....worn insulation, burnt wire, or even an internal break at the coil. Try disconnecting the kill wire from the coil and see if you get consistent spark.

There are also flywheel magnets and a flywheel key in the system. If the key is slightly sheared it might throw the timing off. Magnets (I hear) dont go very often, and if they did youd know (they would be seen somewhere, or at least shards of them).

Only other thing left is the wire that comes off the coil, and the end that snaps onto the spark plug. Ive had one that was corroded and only making intermittent contact.

Can also try looking at safety switches for the machine itself, they might prevent spark (just last year I had to bypass the clutch safety switch on my tractor, because it was preventing spark and engine turnover)

Is the "sometimes spark" while you are trying to start it? Or during running? While trying to start, the starter needs to crank the engine at a certain RPM before it will fire (I think its a minimum of 250 RPM). Either thru a low battery or weak starter its possible you arent spinning the engine fast enough to make spark.

 

[eljefino]

The kill wire ends in a terminal down by the governor that I removed for testing purposes. This eliminates every possible kill switch.

Mower also had a bunch of starter interlocks that also are out of the picture now.

Story is it suddenly didn't start one day, but did the next, and now it's dead again. So a flywheel magnet gone missing is out of the picture. Cranks good & fast, have a newish battery that I keep throwing a charger on. I have the fuel petcock shut off so she won't flood until I get spark back.

 

[Bill Kapaun]

Briggs will have a Model, Type & Code.
Code is the DOM, YYMMDDzz
You might remove the coil and clean up any rust etc. Gap should be about .012", but a business card will get it close enough.
Sometimes mice can get in there and chew on the wire, shorting it. It's not as uncommon as one would expect/
IF the flywheel key is sheared, you'll still get spark. Just not at the right time.

 

[lars11]

What to google for to find the downloadable briggs manual? Could not find anything useful myself...

 

[ChrisJH]

I could swear there was a PDF doc that I had, but it might have been this instead:

http://faqs.custhelp.com/cgi-bin/faqs.cf...li=&p_topview=1