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You should be seeing a make and break of continuity with ground at the power transistor, not sure of which leads. If that doesn't happen, you will never see a spark. It's the breaking of the coil ground path that causes the spark.

Also do a coil function test. Apply 12v to one coil connector, and ground the other. Install a spark plug checker in the wire from coil to dizzy. Make and break the ground and see if you get a spark at the checker. If not, swap 12v+ and ground wire and try again.

Since you have a pulsing 5v signal at the PT, the ecu is good because it's sending the spark signal, and the ecu is getting power, or it wouldn't be sending the 5v signal. This leaves the coil and PT as failure points. Other minor possibilities are the dizzy cap, coil wire to dizzy, dizzy rotor.


Well, shoot. No 12v at the coil primary. I suspect the female connector right now. Could have been operator error, but I used my new piercing probe to pierce one of the wires going to that coil primary connector and, in order to make sure I had right wire pierced, I checked for continuity at the connector and could not get it. I might try chopping off the connector and connecting the wires directly and see if that works.

Gotta get these kids to bed.

Retested the coil. Its good.

1991 Montero LS (LWB) 3.0L V6 Stock 205K Miles