Mercruiser 470 Mystery - Burning out Pertronix ignition?

[Mkongsiri]

Hello all,

I just purchased a 1986 Wellcraft 190 American fitted with a Mercruiser 170HP 3.7l engine. The boat would crank but would not start and I discovered that I was not getting spark to any cylinder. Removing the distributor cap, I see it was outfitted with the OE points system. Coil tested alright as far as I could see so I decided to just upgrade it to the Pertronix Ignitor II and Pertroinix II coil. I did remove the purple resistor wire from the choke and just put a jumper in from the battery to the positive terminal of the coil just to test the system. After replacing the components, I got spark and the engine started up. WhenI went to adjust the timing, I found the engine would no longer start. After testing, I found no spark again?!?!!?!?!!?! Thought the Ignitor II hall sensor may have gone bad, so I replaced it with ANOTHER new unit. Same thing happened, got spark, started the engine. Disconnected jumper and now it will no longer deliver spark. Could it be the jumper is damaging the ignitor circuitry? I know the positive wire is supposed to receive 12v so Im not sure what else could be causing this to happen? I dont see how I can be overvolting the system and Im not sure why the origional coil/points had failed....

 

[salty3rd]

Disconnected jumper and now it will no longer deliver spark. Could it be the jumper is damaging the ignitor circuitry? I know the positive wire is supposed to receive 12v so Im not sure what else could be causing this to happen? I dont see how I can be overvolting the system and Im not sure why the origional coil/points had failed....

So if you put the jumper wire back in will it run?

 

[Mkongsiri]

So if you put the jumper wire back in will it run?

No, I am no longer getting any spark again with the jumper attached.

 

[salty3rd]

I would check all wiring going to the coil, the dist cap, plug wires and make sure the rotor is spinning when you crank it over. I have never heard of coils burning up that quick, doesnt mean it cant happen. Is the cap in good shape? no cracks?

 

[stonyloam]

Try removing the gray tachometer wire from the coil - and give it a try.
You can test the coil by removing all of the wires from the coil -, pull the center wire from the cap and lay it close to bare engine metal. Take a piece of insulated wire and attach to the coil -. Turn on the ignition and make sure you have 12v to the coil +. Briefly touch the wire on the - to ground. You should get a nice blue spark from the center wire every time you remove the wire from ground.

 

[stonyloam]

Read this http://www.jalopyjournal.com/forum/threads/testing-a-pertronix.363494/

 

[Mkongsiri]

Well a call to Pertronix support led to the soluition - I had read on another post on installing the Pertronix to tap down on the center magnetic ring and then trim it so it would slide down the shaft and could be aligned with the ignition module. Of course, I didnt need to do that! I just wanted to test the ignition out first so I simply trmmed the rotor down a bit to test fire. When it ran, I figured it would work ok without trimming the ring and I didnt want to risk damaging it so I left it alone. Well Pertronix suggested to adjust ring to the correct installation height (bottom of ring flush with bottom of ignition module) Voila, it worked. Occasionally, it pays to follow the instructions...:facepalm: