No spark

[Freddie21]

This reminds me of how we used to check a 9v battery by putting it to our tongues. How do you check for 120\240 volts a-c?

 

[johnny7]

I recently came to visit my daughter and she said her lawn mower will not run first I replaced the spark plug still no spark then I pulled the pull rope cover off and inspected the coil found that it was Rusty apparently been leaving it outside so I've replaced the coil clean the flywheel and still no spark any help would be appreciated

Is it possible you have a new 'bad' coil? I keep the following as a reference
Coils and resistance measures
B - base
K - kill
S - spark

B - K 2k - 18k
B - S 2k - 18k
K - S 10k - 30k

Mower coil
Red probe to Spark boot
Black probe to base ground
Should show 2.5 to 5K
If infinity, then the coil is open and no good

 

[Zue]

Make sure coil is not installed upside down.

 

[Yabadabadoo]

Also note that the magneto "module" is polarity sensitive
If you put it on upside down it will not work ( unless it was a factory reject )
Well it will work but the spark will be very weak & way out of time
Most go on with the kill wire down which looks wrong because the HT lead seems to going the wrong way
Some have "This Side UP ' or "cylinder side " or "Engine Side" cast into them.
There was a batch on Evilpay down here a few years ago where the writing was on the wrong side
There was also a batch that were wired wrong and would only work if installed upside down that did not have the writing on them .
Simple test for the magnet strength is to fit the coil as far away as the slot will allow then bring the magnet around and loosen the screws
A good magnet will cause the magneto to snap onto it quite strongly

Is it possible you have a new 'bad' coil? I keep the following as a reference
Coils and resistance measures
B - base
K - kill
S - spark

B - K 2k - 18k
B - S 2k - 18k
K - S 10k - 30k

Mower coil
Red probe to Spark boot
Black probe to base ground
Should show 2.5 to 5K
If infinity, then the coil is open and no good

Havent been on the forum in long time and thankful for this thread and all the LB experts lending hand to this issue, I HAVE THE IDENTICAL ISSUE with my 1980s LB and this thread should help me maybe resolve. I'm pretty handy but know nothing about electrical
Likewise put a new ????? ( magnetic thing on flywheel, im old here and blanking on name )on it and still no spark. I suspect it relates to kill switch, who i bought it from installed makeshift kill switch to the housing with a toggle switch and a wire or two disconnected. If i come back with a pic of that i bet one of you guys can tell me what to do with it, suspect that could be my problem with a simple fix. This is a great thread, thanks from me as well for all this input from all.

 

[mgmine]

I assume that this is a newer lawnmower the type that you have to hold the handle down in order to start it. At the point where the handle meets the connection on the mower pull that lever back with your finger. The zone control cable may not be working properly and not fully releasing the cutoff switch. That would cause the problem that you are facing.

 

[Rondoman]

Look for a dirt dauber wasp nest anywhere on the electrical system. They take no prisoners.

 

[Midnight_Rider]

How old is the mower, does it have any safety devices such as a handle that has to be held against the pushbar , or a kill button ? I've seen brand new fresh out of thw box coils that were no good,and it only requires a multi meter to test a coil to see if it is within specs.. Remove a known working spark plug from anything that runs properly and stick it into the spark plug boot,ground the spark plug tip against a head bolt while spinning engine over. If no spark then you've eliminated the spark plug as the problem. Borrow a coil off of a know running like brand engine and swap it out to ascertain if it is the coil or not,test the spark plug wire for resistance using a multimeter to see if its bad or not..

 

[Bob2]

To confirm whether the coil is producing a spark, disconnect the small wire that is connected to a tab on the coil and retest. This will disable any of the safety switches that may be keeping the coil from generating a spark. If you now have spark, correct the safety switch problem. NOTE: If the engine starts, you will have to reconnect the wire to the coil to stop the engine.

If there is still no spark, recheck the air gap using a business card or feeler gauge and also confirm the orientation of the coil mounting as another reply already stated. I recently replaced a failed coil on an older machine with a non-OEM coil and had to mount it upside down from what would have been the normal direction for the plug wires to exit in order for it to generate a spark.

 

[puppypantz]

I

I recently came to visit my daughter and she said her lawn mower will not run first I replaced the spark plug still no spark then I pulled the pull rope cover off and inspected the coil found that it was Rusty apparently been leaving it outside so I've replaced the coil clean the flywheel and still no spark any help would be appreciated

Did you actually ground the spark plug to the mower when you checked for spark? It won't spark if held in the air. I looked thru all of the responses and it wasn't mentioned unless maybe I missed it.

 

[The Specialist]

You probably sheared the flywheel key! Remove the starting cover to show the flywheel. Remove the centre nut. If it has a starting cup, remove it and put the nut on so it’s at the top of the crankshaft. Turn the magnet so that it’s on the back right hand side of the engine (by where the cover bolt goes-that area. Take a prybar and put under the flywheel where the magnet would be. Gently take a hammer and hit the top of the nut on the crankshaft while pressing down on the prybar. This should pop the flywheel. Remove the nut and the flywheel and there is a flywheel key. I’m sure you will find that it’s sheared. When you get a new one, put the flywheel on, and you will see the space for the key. Put it in, then the starting cup, washer and nut. To tighten so you don’t shear it again. Hold the blade with one hand and tighten the nut down with the socket and ratchet with the other hand. Put the rest back together. You could also probably take the new coil back and put the old one back on. Note: while working on the machine, remove the spark plug for your safety.