I can't tell what is an 8 and what is a 6 on that diagram leshby, I have been reading the red wire to the ammeter and the black wire to the master switch both as 8. OK, let's call the black wire 6, it makes more sense and I'm sure you are right. Now, black wire 6 was the one you used to stop the Briggs engine, and it did that successfully. You have connected the same wire to the Tecumseh's green wire, and it did not produce the same result: it did not stop the engine. It sounds as if contact is not being made somewhere in the circuit that begins with black wire 6.
Test 1: Can you connect wire 6 to green wire T (for Tecumseh), then go to the first connector in wire 6, where it becomes wire 10, before you get to the master switch. Separate the connector, start the engine, and ground wire 6 with a piece of wire, jumper lead, or whatever you have. This should stop the engine: it should be exactly the same as grounding the spade connector on wire T. If it doesn't stop the engine, wire 6 has a break in it.
Test 2: If the engine does stop in Test 1, go to the other end of wire 10, the clutch switch. Restart the engine, and ground wire 10 at the input terminal of the clutch switch. This should stop the engine unless wire 10 has a break in it.
Test 3: If the engine does stop in Test 2, go to black wire 16 where it attaches to the brake switch. Restart the engine and ground wire 16 at the switch. This should stop the engine unless wire 16 has a break in it.
Please let us know the outcome of these tests. Essentially, if the kill system is not working, there is a broken or disconnected wire in that system, and we just need to go through the sections until we find the problem.
