Briggs Stratton ignition question .....

Crazy Horse · Aug 21, 2015

I'm not getting any spark from the ignition system on a Briggs and Stratton pull-start air cooled engine (on a Coleman generator set), about 15-20 years old. The on-off switch (which is really just a ground switch) is working, I tested it separately. I did some testing and the wire which goes to the ground switch (from the transformer magnet mounted above the flywheel) is continuous to ground when disconnected from the ground switch. Obviously, it should not be grounded if I am expecting the plug to fire. When that wire wire is connected to the ground switch and the switch is in the on or off position, that wire is grounded so no spark.

But I never did test the wire to see if it is grounded all the time when the flywheel is spinning. Maybe when the spark impulse occurs, the wire is not grounded if the switch is in the on position? I'm not sure how these things work. This happened all of a sudden, actually the tractor fired for a few seconds before the ignition went dead.

And I had just previous to all of this bypassed the diaphragm style fuel pump which feeds fuel to the carb float bowl. Since the fuel tank is well above the carburetor, I just use gravity feed. I don't think that this could have any connection to the lack of spark unless there is some mystery bit of engineering in there that is hidden away from me.

Any suggestions about this and some possible further trouble shooting or checking is appreciated.

Fordfarmer · Aug 21, 2015

If that wire is grounded when the switch is "on", that's your problem.

used red MN · Aug 21, 2015

How are determining the kill switch wire is "grounded" all the time? With a continuity meter (ohms) I assume. Yes the wire will show continuity to the engine block all the time because it is connected to the coil windings which the opposite pole of the winding is connected to the block. Yes, there will only be elecrical pulses on the kill wire when the coil is pulsing sparks. How are you testing the spark output of the coil?

Crazy Horse · Aug 21, 2015

For yourself (and Ford Farmer also) ...... yes, continuity tested with an ohm meter.

So it sounds like the wire I'm referring to should be grounded any time at all (regardless of the position of the kill switch) EXCEPT for when the switch is "on" and the ignition system is sending out hot voltage to the plug? In other words, always grounded when the switch is in the "off" position, and when the switch is "on", the wire is grounded unless a spark is being generated?

Spark test done with the current engine spark plug (removed and hooked to the plug wire and grounded to the engine).... and then a second test with another spark plug which I made up into a tool to test spark (a plug with a ground wire and a ground clip).

Steve@Advance · Aug 21, 2015

Check the kill wire with it disconnected from the coil. Should show open with the switch on. There may be other safety kill switches, like low oil, etc.

Check the spark with the wire disconnected. If it sparks, the wire is grounded. If no spark replace the coil.

Jeff NWOH · Aug 21, 2015

Is that Briggs old enough to have points? Check the first 2 digits of the engine code. If its lower than 83 it probably has points and condenser under the flywheel and that's most likely your problem.

If its newer than '83 its electronic. The wire to the shutoff switch connects to ground to kill the engine. It should spark with it disconnected. If it doesn't, either the coil, sparkplug, or the magnet on the flywheel is bad.

MARK ROBKE · Aug 21, 2015

There would be a certain amount of resistance thru the coil,but almost zero ohms thru the wire itself.So if it is zero ohms,I would check the wire for being grounded-bare spot touching block-or another switch wired in series being grounded out as others have posted,like safety shut-down,neutral safety,etc.Mark

Crazy Horse · Aug 21, 2015

It's mid 90's so it has electronic ignition. I'm not handy right now to the generator set but I will do some checking based on all the good advice given to me here on the forum ...... thanks everyone, I think I'm pointed in the right direction.

Angle Iron · Aug 21, 2015

(quoted from post at 06:43:31 08/21/15) I'm not getting any spark from the ignition system on a Briggs and Stratton pull-start air cooled engine (on a Coleman generator set), about 15-20 years old. The on-off switch (which is really just a ground switch) is working, I tested it separately. I did some testing and the wire which goes to the ground switch (from the transformer magnet mounted above the flywheel) is continuous to ground when disconnected from the ground switch. Obviously, it should not be grounded if I am expecting the plug to fire. When that wire wire is connected to the ground switch and the switch is in the on or off position, that wire is grounded so no spark.

But I never did test the wire to see if it is grounded all the time when the flywheel is spinning. Maybe when the spark impulse occurs, the wire is not grounded if the switch is in the on position? I'm not sure how these things work. This happened all of a sudden, actually the tractor fired for a few seconds before the ignition went dead.

And I had just previous to all of this bypassed the diaphragm style fuel pump which feeds fuel to the carb float bowl. Since the fuel tank is well above the carburetor, I just use gravity feed. I don't think that this could have any connection to the lack of spark unless there is some mystery bit of engineering in there that is hidden away from me.

Any suggestions about this and some possible further trouble shooting or checking is appreciated.

y the late 80 Briggs had already started using low oil cut off switches on some if not all generators. Just something else to check. Pulled my tail off on one setting on uneven ground, would not start. Leveled it and started on the next pull.

Anonymous-0 · Aug 21, 2015

(quoted from post at 13:09:16 08/21/15) Check the kill wire with it disconnected from the coil. Should show open with the switch on. There may be other safety kill switches, like low oil, etc.

Check the spark with the wire disconnected. If it sparks, the wire is grounded. If no spark replace the coil.

This.

gwstang · Aug 21, 2015

Yes! I have an older generator and the low oil (even though it is full) would get me occasionally. I unplugged that thing and no more problems with generator cranking!!!

Texasmark1 · Aug 22, 2015

Just because it seems to be at DC ground doesn't mean it's at AC ground. The magneto is a transformer and the physics of a transformer are such that when energized (the magnet on the flywheel passing by the secondary) each turn will have a voltage proportional to the applied voltage and the turns ratio. If any ONE turn violates this rule, the transformer does what It has to/can to bring this single turn voltage back to where it belongs, even if it means sucking up all the energy in the other windings and core and all that.

When you ground the kill switch, you are shorting out at least one turn and probably numerous and as a result, there is no energy left in the mag to fire the plug....the engine quits.

So for a problem, if nothing is obvious then you may have worn the varnish off a turn or two inside the mag. and you have a couple of wires touching amounting to the same thing as stated above. Otherwise you may have a corroded or bad connection between a wire and connector.

Briggs Stratton ignition question .....

Crazy Horse

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Fordfarmer

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used red MN

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Crazy Horse

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Steve@Advance

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Jeff NWOH

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MARK ROBKE

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Crazy Horse

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Angle Iron

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Anonymous-0

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gwstang

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Texasmark1

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