Help with no fire!

[johnrolf]

1972 20hp Mercury Thunderbolt ignition (pull start) engine is firing only on the top cylinder. I've swapped the coil wires to check for a bad coil and that's not the problem. Both coils are good. Spark plugs and wires are good also. I tried pulling the flywheel and trace the bad wire(green)down. I can see where it goes in, but can't get the flywheel off to see where it connects to. Where is the power pack on the engine, or does it not have one? What could be causing the engine to fire on 1 cylinder only?

 

[achris]

Re: Help with no fire!

Have you lost spark on that cylinder or is the cylinder not firing? If there is spark but the cylinder isn't firing, I'd suspect the lower crankshaft seal.<br /><br />Those engines have an 'ignition module' that lives under the flywheel.<br /><br />Chris..........

 

[johnrolf]

Re: Help with no fire!

I think that I have spark on that plug wire. It was enough to shock the heck out of me through the rubber spark plug wire. I can crank the engine and it runs. When I pull the top plug wire (hooked to the left coil) the engine dies. When I plug bak in the top spark plug and crank back up and pull the bottom plug wire (hooked to the right coil) nothing changes, keeps on running on just one cylinder. I have swapped plug wires on the cylinders and both cylinders run, just not at the same time. Very strange though seeing as how the plug wire that won't run the cylinder has enough zap to it to shock me. Any ideas?

 

[johnrolf]

Re: Help with no fire!

^

 

[johnrolf]

Re: Help with no fire!

^