ignition sw. mystery

My Merc 170 quit starting, I can jump start it at the solenoid and I can jump start it at the ign. sw. with the red and yel/rd wire lifted. ( The engine is just turning over not running. This tells me the start wiring is good thru the neutral safety sw. to the solenoid.) When I replace the wires on the switch, I get nothing.....when I lift the purple run wire off the sw. the engine will turn over with the key? when i replace the purple wire on the sw. I get nothing...could the purple wire be grounded some where?? It has an electric choke on the engine...stuck in dry dock..Thanks for the help P.S. I rang out the sw. and it's good.

Ayuh,..... Sounds like a bad switch,.....
The purple wire is the ignition circuit,.... Check for power at the coil's (+) tiny terminal,.....

I checked the sw. and I can read voltage thru it , when the purple is lifted...further isolating the purple by the electric choke and at the coil.( with the key on and purple connected, I could feel the purple wire getting hot) does that mean the resistance wire is working? Thanks

ourgang said:

... P.S. I rang out the sw. and it's good....

Click to expand...

If you did that test with a multimeter on the ohms scale, you didn't prove out anything....you need to test the switch with much higher current (amps, not milliamps) to verify it.

the purple wire getting 'hot' means a bad connection or a bad wire...

Hello, I was able to read the ohms on the purple resistance wire from the harness connector, by the red breaker button, to the coil. I separated the two wires going to the + on the coil and read 1.4 ohms without the electric choke connected. When I reconnected all but the choke, it was still a no go. The engine will crank when I lift the purple wire at the key sw....but nothing when I reconnect and try again...I'm going to run a temporary purple from the key sw. to the coil and see what happens...

I'd be more inclined to check for voltage drops, from the battery to the switch...

You may also want to separate the main engine harness plug...sometimes the pins/sockets corrode and cause these types of issues...