No spark in lower cylinder

[janderson11881]

1966 johnson 40 rds28b. Top cylinder sparks fine, none in lower. swapped coils no change, possibly points or pack? What is the best way to test this. Also, the two wires on the ignition switched marked "M" seem like they link together somewhere. Using a continuity tester they show a continuous circuit even when disconnected from the switch. Is this right? This seems to just be grounding the ignition when turned on. Motor still cranks fine just wondering if this is part of my problem. Thanks

 

[samo_ott]

Re: No spark in lower cylinder

The coils are under the flywheel on that model, right? So you pulled the flywheel and reversed them? That's a lot of work.

The two M connections on the ignition switch should be shorted together when the key is in the off position. This shorts the two coils together and stops the engine. Then there's also the vacuum cut off switch to check to see if it's shorting out.

Is it mechanical or electric shift?

I attached the wiring diagram for the '66 33hp if it'll help. I believe it's very similar.

 

[janderson11881]

Re: No spark in lower cylinder

Thanks for the diagram. What I'm seeing in my case is the two m wires seem to be connected somewhere besides the ignition switch. When I disconnect them from the switch they still make a continuous circuit. I've traced it up under the coils but don't really want to pull the whole assembly apart if I don't have to. Is there anything that comes to mind that would cause this? Thanks again

 

[VaBlue]

Re: No spark in lower cylinder

If the two wires were always shorted together you wouldn't get any spark at all, so I wouldn't think that is your problem. You should check to make sure all of the wiring is good (ie: not corroded), especially ground connections. Otherwise, the power pack and other mechanics involved (upstream of the coils since you already verified that everything between the coils and plugs are good) are more likely than a non-moving, uncorroded, wire suddenly shorting. Can you swap the power pack leads going to the coils? If so, and you get spark on the lower cyl, but not the top, it's probably the power pack.

But you have points, right? Check those, too, even if the pp lead swap moves the problem.

 

[lindy46]

Re: No spark in lower cylinder

Could be points, could be plug wires, or could be cut-out switch malfunction. Cut out switch kills the bottom cylinder in a runaway situation. Disconnect the wire from the switch and see if it runs on both cylinders - if it does, then it's the cut-out switch.