Briggs and Stratton coil .

Charles in Aus. · Apr 11, 2021

My mower won't spark. A 675 series 190cc engine with this style of coil .

I get 9000 ohms from it which I thought was fine . Am I missing something here . Winter is approaching and I have a few more cuts to do before I pack it away for the season .

old · Apr 11, 2021

If it is like most there is a shut off in the carb throttle linkage which can go bad. Pull the wire off of it and see if you have spark. I have more then one mower that has had that problem

Janicholson · Apr 11, 2021

They have three components, a primary low voltage coil, a secondary high voltage coil, and a trigger that senses magnetic
pulses to make the magnetic field collapse. making the voltage. The spark plug wire to ground should have the ohms you show,
but the other components may be bad. If the kill citcuit is open, and no spark, replace it. Jim

MarkB_MI · Apr 12, 2021

The gap between the coil and flywheel is critical.
B & S coil gap spec

MtMan · Apr 12, 2021

Here is my way of checking a B&S coil. With an OHM meter, measure from the wire that connects to the points to the wire with the
ring terminal that grounds under the coil mounting screw. You should read O OHMS. Then measure the plug wire to the same ring wire
and you should get 4 to 8 OHMS. If both readings are good, the coil is good. If you read infinity in either place, the coil is
bad. Hope this helps.

Charles in Aus. · Apr 12, 2021

Thanks very much Old , Jim and Mark ( that link is very useful Mark ) .
I did check the kill switch first , it works properly and I removed the coil cleaned the contact areas and adjusted the gap but had no result . So I suppose it's a new coil but identifying the right one is difficult .
I suspect this mower is cursed , it's gone from working fine to having a snapped gear box cable , sheared blade disc bolts , a sudden throttle lever failure and no spark all at the same time . If I were paranoid I'd think it was sabotage :?

Charles in Aus. · Apr 12, 2021

I'll try that tomorrow Mt Man , thanks .

Geo-TH,In · Apr 12, 2021

Mark.
I gap my coil by using 3 one dollar bills between coil and magnets. Clean rust out flywheel using wire brush on drill.
Three $20 work too.

John T · Apr 12, 2021

1) A simple low voltage ohm meter type ohms/continuity test can show if a coil is definitely BAD (like open or shorted)

2) HOWEVER it can NOT show/prove its GOOD since it may still exhibit High Voltage Breakdown under actual High Voltage and
temperature conditions.

IE just because it passes a low voltage ohms/continuity test DOES NOT PROVE ITS GOOD even if sure it can show if its
definitely BAD

THAT BEING SAID a few common (among other) causes of no spark may be as simple as 1) There's excess rust/corrosion on the
coil laminations or the magnets on the flywheel (clean both up) orrrrrrrrrrrr 2) The air gap from flywheel to coil isnt
correct (check gap) orrrrrrrrrrr 3) The Grounding Kill Wire (often located on the throttle assembly) is shorted out

John T

cwtech · Apr 12, 2021

Charles:

B&S engines use an aluminum flywheel key. ...The condition of that key is critical to engine timing for starting. ...If the key has ANY marring on its edges, replace the key before buying a new coil.

Your comment about the sheared blade disc bolts make me think an object was struck. ....This usually causes the flywheel key to upset the ignition timing while trying to start.

Sometimes an engine with a sheared flywheel key will continue to run, but not re-start. ...If the key is sheared completely, the engine usually dies right then.

Do NOT substitute a steel key.

I believe B&S 222698s is the correct key for your engine.

Determined · Apr 12, 2021

(quoted from post at 07:59:35 04/12/21)
Thanks very much Old , Jim and Mark ( that link is very useful Mark ) .
I did check the kill switch first , it works properly and I removed the coil cleaned the contact areas and adjusted the gap but had no result . So I suppose it's a new coil but identifying the right one is difficult .
I suspect this mower is cursed , it's gone from working fine to having a snapped gear box cable , sheared blade disc bolts , a sudden throttle lever failure and no spark all at the same time . If I were paranoid I'd think it was sabotage :?

A couple of thoughts your coil is marked cyl side because some of them can be physically mounted backwards on the engine and they will not work that way.

Other thought was you mentioned sheared blade bolts, have you repaired them yet?

Some of those engines depend on the inertia provided from the blade being attached to start.

kris Jensen · Apr 12, 2021

g'day: I have a number of B/S motors and mowers. Sometimes from wintering over with less than
ideal storage they refuse to start. (because of rust build up) My solution has always been to remove flywheel and polish the
magnet surface with fine sandpaper or emery cloth, make sure contact points on the coil are clean as well
light polish with emery cloth, set air gap, reinstall flywheel, and you are back cutting grass or whatever.
Just did that a couple of weeks ago to my mowers. Best to you. Kris
ps. 50 years ago had a lawn boy that would not start after having lunch. Finally in frustration I took off the flywheel
and discovered a blade of dry grass stuck between the points. (old time system) cleaned and reassembled and started on first pull.

wore out · Apr 12, 2021

There's no need to "polish" the magnets, the only time rust on the flywheel or "armature" affects spark is when it's severe enough to cause "drag"/physical contact between them.

Left the flaming begin!

Dusty MI · Apr 12, 2021

Because emery on emery cloth is a conductor do not use it on ignition points, it can leave conducting particles behind. Sandpaper is a nonconductor.

John T · Apr 12, 2021

Hey Dusty, Actually I prefer a points file to clean up a set of points as I agree with you and don't like to leave any
residue. I use a rag or non abrasive as possible when I clean off the flywheel insert magnets or coils on small engines to
remove rust which in my experience helps.

John T

Charles in Aus. · Apr 12, 2021

Thanks to everyone

This discussion has certainly given me many possible solutions . I will try each and every one in turn , I can see now why so many mowers turn up at the side of the road , for a serviceman to try to make a living from problems like this the cost must come close to a new one .
It's my favourite mower and still looks good .
I've checked all the straightforward things , flywheel off now to look at what's under there.

T.R.K. · Apr 12, 2021

Although an ohm test is one of the tests for that ignition module, it won't tell you if the 'trigger' circuit is actually working.

What we do here in the shop is check the magnet(s) and make sure a screw driver snaps to them with a pretty firm snap, check the air gap,
(it should be .010 to .012 inch) disconnect the kill wire and if it still doesn't spark, install a new module.

JDBRIDER · Apr 12, 2021

I use a piece of aluminum cut from an aluminum can as a feeler gauge to set the air gap. I believe it takes 2 thicknesses.

kencombs · Apr 13, 2021

Years ago my wife bought a nail file covered with very fine diamond dust. Guess what is my favorite points file? Just have to be careful and not get caught.

gears · Apr 13, 2021

Unlike Geo, I use two $2 bills for gapping my coils but with one folded in half.

Theyre right about that stupid trigger circuit though. Ive replaced more coils in the last 5 years for no spark conditions (and fixed it) than I have over the previous 25... and has anyone else noticed that the new replacements are different design than the old OEM Magnatrons?

Jo Bird · Apr 14, 2021

(quoted from post at 02:57:09 04/13/21)
Thanks to everyone
This discussion has certainly given me many possible solutions . I will try each and every one in turn , I can see now why so many mowers turn up at the side of the road , for a serviceman to try to make a living from problems like this the cost must come close to a new one .
It's my favourite mower and still looks good .
I've checked all the straightforward things , flywheel off now to look at what's under there.

ince you stated " sheared blade disc bolts , a sudden throttle lever failure and no spark all at the same time " you jogged my memory. Check the key under the flywheel, they tend to shear when the blade makes a sudden stop and will throw the timing off, hence the engine wont start ...

Charles in Aus. · Apr 15, 2021

The latest , in fact all the replies so far are logical and make perfect sense. I thank each and every one for their responses .

Trying to start and working on this accursed thing has BuGG er ed my back . I'm in a brace for a day or two until it calms down . I had spinal fusion in 2001 so this self propelled unit is vital . It's supposed to stop my back from hurting not make it worse .

An update and some photos as soon as I'm able .

DMartin9N-2N · Apr 15, 2021

Good morning, wore-out: I agree there is no need to clean slight rust off the magnets, unless it is dragging against the laminated armature. Even then, I suspect it is more of a housekeeping thing than a necessity. most everybody has an opinion, that is mine....

Dennis M. in W. Tenn.

K Effective · Apr 15, 2021

I'm actually surprised Charles has a lawn mower in Australia. I figured all vegetation was consumed by roos or wallabies or roaming herds of sheep, maybe even dingos. That giant bat you posted a picture of might like grass. Who knew?

Good luck with your mower. And your back.

Briggs and Stratton coil .

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