no spark, 1981 Mercury 4.5

[kurtloup]

Over the weekend, I replaced the ignition wires on my recently purchased 1981 Mercury 4.5 with 10 gauge wire.* Once the wiring was replaced, I tried to start the motor for the first time.* Unfortunately, I am getting no spark.

I checked the continuity of the spark plug wire and it read zero ohms. I also checked the continuity of the points. There was zero ohms with the points closed and with the points open. If I tested from either contact to either the positive or negative post of the yellow and red ignition coil that you can see in the above picture, the ohms also read zero. Is this narrowing down the problem? What should I check next? Thanks.

 

[guyjg]

Start w/replacing the heavily corroded wires in the top pic. When blindly measuring between two points, "0" ohms only means there is continuity. You need a wiring schematic to properly check w/an ohmmeter. Continuity can be from a deliberate direct short between two points--a straight wire--or in a round about manner via a defective component--a shorted condenser--which is also a direct short. Condensers are cheap and break down often.

 

[kurtloup]

Thanks for the info. Are wiring schematics included in Mercury shop manuals? I went to the library and picked up aftermarket repair manuals, but they did not include ignition information. The corroded wires were replaced over the weekend.

 

[guyjg]

Are wiring schematics included in Mercury shop manuals?

Yes, basic diagrams.