No Spark with Plug, But Spark from Lead.

[DazzaJay]

It's a Genuine Briggs&Stratton coil from a mower shop.

The old coil stopped working, which is why we got the new one.

But I'm wondering now, if the Magnets in the flyweel could have gone a bit bad. - If they are not as strong as they should be, wouldnt they create less power in the coil?
(thinking that the older one would have been affected first because it's older, new one, because it's newer and would be in better condition was able to run for a short while? but not it cant either.)

 

[Boudreaux In Eunice La.]

It's a Genuine Briggs&Stratton coil from a mower shop.

The old coil stopped working, which is why we got the new one.

But I'm wondering now, if the Magnets in the flyweel could have gone a bit bad. - If they are not as strong as they should be, wouldnt they create less power in the coil?
(thinking that the older one would have been affected first because it's older, new one, because it's newer and would be in better condition was able to run for a short while? but not it cant either.)

Yes the magnets could be weak, and you did ask that in your first post......

You did say that the mounting areas were shiny...... What I do to make sure is I take a flat file and rub it across the mounting posts VERY LIGHTLY and then take a brass wire wheel on a cordless drill then clean the coil surfaces where they meet the posts and the legs that face the flywheel.........

Then I spray with carb cleaner and blow dry with a air gun or let sit a few minutes in the sun....

Yes I have seen magnets go bad on older chainsaws and a few Briggs engines.... So your magnets maybe are bad....

Clean the flywheel mags with a brass tooth brush and spray some carb clean then try that........ Also the file trick that I said earlier.........

Let us know Mon Ami ~!~!

 

[Boudreaux In Eunice La.]

You never did say you had a Briggs engine or the model number........

What is your engine model number by the way ???

 

[Boudreaux In Eunice La.]

Also is it a rider mower ????? You said you had spark for a day........ If you have a rider mower then you might have zapped the coil with some stray voltage some kind of way ..........

 

[DazzaJay]

Yeah, She's a Rover Ride-On Mower.
and she looks quite old.

It's previously had a complete re-wiring done on it (A few years ago).

And the Engine is a Briggs&Stratton:
Model: 257707
Type: 0129-01
Code: 92021011

 

[EngineMan]

Coil (armature) part number 398811 air gap .014 valves gap In.005 Ex.009

 

[bertsmobile1]

While it is very rare, the magnets can go weak particulalry it the magneto legs ( or something else ) has been rubbing on them.
If they are in good conditiion they should cause a screwdriver to pull in from 1 " out.
The coil itself could be leaking.
Try spinning the engine late at night in a dark place and look for sparks around the coil running across the surfaces,

 

[Boudreaux In Eunice La.]

Dazz a business card is 12 to 14 thou.... My cards are 13 I think..... That's what I use to gap my coils with.... My service tags are 11 thou and that's what I use for the small 2 to 4 HP engines......

Years ago I had all different coil gap gauges but when I sold out all that went with the inventory...... I wish I still had half the stuff I had back in the early 90's and late 80's...........

Bert gave you some great advice on the leaking coil.....

Let us know Mon Ami ~!~!

 

[DazzaJay]

I've had the local small engines guy have a look at it last night, and even he's confused.

he's described it as a "very weak spark" and he's currently looking to see if he has a spare flywheel laying around, as he's thinking Magnets too.

 

[DazzaJay]

Ok.... It's solved. and it's stupider than we imagined.

It was the Coil. (Both the original and the Genuine New Replacement)

So, Let's go through the entire list of how we came to this conclusion.


No Spark.
Replaced Spark Plug. Sill no Spark.
Replaced Spark Plug Again. Sill no Spark.
Replaced Coil & Lead with B&S Genuine Replacement. Still no Spark.
Replaced Flyeheel. Still No Spark.

So, from this point we decided to work backwards from the flywheel. Seeing as we already forked out for an expensive B&S Genuine Coil, we instead ordered in a cheapo chinese one...

Replaced Genuine Coil with Cheap Chinese Coil.
IT WORKS!

Which means, When the engine first failed, it was the Coil at Fault. and when we replaced it with a Genuine B&S Coil, the Replacement from B&S Must have been Dead On Arrival.

What a bloody headache that was. now to get a refund on the genuine B&S Coil that doesnt work.....