What is the extra spade tab on the coil for is this s ground

Your key switch may be faulty. Can you ground the coil manually to bypass it? If not, the coil itself may be bad if grounding the small wire coming off of the spade connector on it, is grounded to the engine or the frame, but I'm guessing it's most likely the key switch. They're cheap on eBay.

To be sure it is the kill switch is easy enough to figure out. But first lets go over how it works picture a ground wire being touched to your spark plug wire the spark would follow it to ground before it got to your spark plug. That is what happens when you hit the kill switch it completes a circuit that sends your spark to ground rather than to your plug. So if we know for sure we are not getting spark to the plug then we only have to disconnect the kill switch to determine if it is the culprit. Pop out the kill switch on most models it just takes a screw driver. when you do look to see if the spades are touching if they are separate them and see if you have fire at the plug sometimes this is what causes the failure. If not proceed with plan A remove the switch and tape off one or both of the spades that connect to it as if they touch it is the same thing as an engaged kill switch and your spark will go to ground. Try the engine again. Are you getting spark to the plug if so then replace the kill switch. if not then follow your wires back to your coil at the flywheel are there any bare spots or is the spade at the coil touching anything. If so repair the wiring or adjust the spade and try again. if still a no go then you have a bad coil

To be sure it is the kill switch is easy enough to figure out. But first lets go over how it works picture a ground wire being touched to your spark plug wire the spark would follow it to ground before it got to your spark plug. That is what happens when you hit the kill switch it completes a circuit that sends your spark to ground rather than to your plug. So if we know for sure we are not getting spark to the plug then we only have to disconnect the kill switch to determine if it is the culprit. Pop out the kill switch on most models it just takes a screw driver. when you do look to see if the spades are touching if they are separate them and see if you have fire at the plug sometimes this is what causes the failure. If not proceed with plan A remove the switch and tape off one or both of the spades that connect to it as if they touch it is the same thing as an engaged kill switch and your spark will go to ground. Try the engine again. Are you getting spark to the plug if so then replace the kill switch. if not then follow your wires back to your coil at the flywheel are there any bare spots or is the spade at the coil touching anything. If so repair the wiring or adjust the spade and try again. if still a no go then you have a bad coil

as said before, there is a ground leed that has a spade which is to be reinstalled in new dist cap. if this ground strap is not reinstalled you will not have spark.

Kind of. Many mower engines stop by grounding out the coil. It is a simple wire that goes to the coil (usually plugs on with a spade connector) then through the wiring of the unit ends up grounding somewhere. You can always pull the wire from the coil and with the switch in the off position test for continuity with a multimeter. You should get almost no resistance (1 Ohm or less). You may just have a bad ignition switch.

There are very few design flaws in the e46 (window regulators, sunroof guides). You just found one of them. BMW put dissimilar metals in the plug and pins in the tail light, and corrosion results. The ground connection corrodes long before the others. Cleaning it is a temporary fix. Replacing the tail light is a temporary fix. Adding a second ground connection is a permanent fix.
In the ground trace on the back of that tail light, you will find a tab for a spade fitting. Make an extra ground wire about 6" long with a spade fitting on one end and a loop on the other end that fits on one of the bolts that holds the tail light in. Do both tail lights while you are at it.
Actually, this was probably not so much a design flaw but rather a case where the plug and the tail light were made by two different suppliers who did not communicate their material selections to each other.

If you are referring to the ignition coil, that is generally a sign that "voltage" is being applied "to it". Not sure if anyone has been messing with the wiring, changed an ignition switch, etc. There is a single "ground" wire that hooks to a spade terminal on the coil. This is for grounding only, if something gets crossed and battery voltage goes to this terminal it will blow the coil about as fast as you turn the key. Hope this helps.

The Black wire will connect to body ground, and it should be a good solid ground and if this wire is not grounded well then you might receive a primary voltage shock if you touch anything that is metal or grounded inside of the vehicle when the engine is running.

The Red wire should be connected to power when the key is in the "Run" position only, and a good place to find that source is one of the "IGN" connections at the fuse panel using a covered female spade connector. Use a test light and be certain that the connection only has power when the key is in the "Run" position, and has no power when the key is in the "Off" or "Accessory" position.

The White or Yellow wire should connect to the "LPS" connection at the fuse panel next to the LPS fuse using a covered female spade connector.

The Green wire will connect to the "-" negative side of the ignition coil or to the "Tach" or "Test" lead that runs from the negative side of the ignition coil. To locate the lead run down the wire from the negative side of the ignition coil and the lead should break off from that wire and it should have a tag on the wire that will say either "Tach" or "Test" (sometimes it is just an empty black wire connector) and that is if the lead does not come straight off from the wire connector at the ignition coil. If there is no lead you can get a wire tap connector to tap into the wire from the negative side of the ignition coil and then use a covered male spade connector to connect the Green wire from the tachometer to the wire tap connector.

Here is a diagram to help assist you and if you can not download the image right click on the image and then select "save picture as..." or "save image as..." and from your image viewer you should be able to read this diagram or print it out, and let me know if you require any further assistance.

The Black wire will connect to body ground, and it should be a good solid ground and if this wire is not grounded well then you might receive a primary voltage shock if you touch anything that is metal or grounded inside of the vehicle when the engine is running.

The Red wire should be connected to power when the key is in the "Run" position only, and a good place to find that source is one of the "IGN" connections at the fuse panel using a covered female spade connector. Use a test light and be certain that the connection only has power when the key is in the "Run" position, and has no power when the key is in the "Off" or "Accy" position.

The White or Yellow wire should connect to the "LPS" connection at the fuse panel next to the LPS fuse using a covered female spade connector.

The Green wire will connect to the "-" negative side of the ignition coil or the primary side of the ignition coil, and for later model GM HEI equipped vehicles this will be the "Tach" connection next to the main "Bat" connection on the distributor cap if the ignition coil is mounted inside of the distributor cap, or to the "Tach" or "Test" lead that runs from the negative side of the ignition coil if the ignition coil is mounted separate from the distributor. To locate the lead run down the wire from the negative side of the ignition coil and the lead should break off from that wire and it should have a tag on the wire that will say either "Tach" or "Test" (sometimes it is just an empty black wire connector) and that is if the lead does not come straight off from the wire connector at the ignition coil. If there is no lead you can get a wire tap connector to tap into the wire from the negative side of the ignition coil and then use a covered male spade connector to connect the Green wire from the tachometer to the wire tap connector.

Here is a diagram to help assist you although it might be hard to make it out, and let me know if you require any further assistance.

The switch grounds the ignition coil through the spade connection to stop the engine. The switch should be mounted in a metal panel (ground). Hope this helps!