Advice? 1993 Mercury V6 200 xri EFI motor Kill switch is In normal RUN position, my motor starts up normally and is running fine. But when I test and throw my Kill switch down, instead of engine stopping like it used to, now the engine only slows , runs rough and my warning horn starts beeping on/off.. Checking my Ignition coil primary input voltages it look like the engine is still being able to run off of the 1, 3 and 5 cylinders with only the cylinders 2, 4 and 6 shutting off.

When I throw the switch back up to RUN positon, then the alarm stops and the engine returns to running normal off of all 6 cylinders.

Any ideas why a kill switch only slows my engine?

One other symptom update.....whenever running the engine and I turn off the key (ignition switch), the engine continues to keep running for 3 or 4 seconds before stopping...it has never previously done this.

I think you have a bad ground.

Mike beat me to it. Check the leads coming out of the kill switch and follow them. I think you'll find it.

I'll check your suggestions further in the morning as the mosquito swarm just chased me in for the evening. I'm looking closely at vo;ltages, especially the grounding associated with the inner switch box which drives cylinders 1,3 and 5 which are the ones appparently not being killed by the safety switch.

the kill circuit is a black/yellow wire coming off the switchbox. if the motor has two switchboxes they both have a kill wire.

When kill circuit is connected to ground it short-circuits the ignition, killing spark.

The black/yellow wire coming off that box you mentioned must have a loose connection, or else an open circuit inside the insulation.

jtexas is right. The only place the kill wires seperate is at the power packs.

I examined wiring and checked tightness of nuts on terminals of my inner switch box. The BLK/YEL wire fell apart when I touched it as only insulation was holding it on. I repaired it and now the kill switch operation is back to normal.

Thanks for the tips..they really helped. The forum is a great resource.