'78 55hp ignition troubleshooting

VaBlue

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Aug 25, 2009
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15
My issue is very similar to MassBassin's problem in another thread - no spark on the bottom cylinder. I don't want to hijack his thread, so here's mine!

I've swapped the coil leads out of the power pack and the spark moved from the top cylinder to the bottom, so I know everything south of the power pack is good. However, when checking resistance for both the sensor and charge coils it shows open between the respective leads and the armature plate (which I suspect is the same as engine ground). Since I don't have the DVA adapter for my multimeter, is it even fair to check the output voltages from either coil (I don't see any voltage, so I hope it isn't fair!)?

Since it does have spark on one cylinder, can I safely assume that both the sensor and charge coils are working and that the problem is the power pack? Obviously, that's the easiest thing to replace short of pulling the flywheel to get at the rest of the ignition assembly. I don't have the necessary tools to pull the flywheel, so if I need to it's heading to the shop. Is it worth the couple hundred for a power pack just to avoid another couple hundred in the shop?

Thanks for the help in advance!
 

VaBlue

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Aug 25, 2009
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Re: '78 55hp ignition troubleshooting

BTW, to add some detail and context... This motor was idle for ~5 years before the last few weeks. Compression is 120# in both cyl's, the carbs have been rebuilt, all new fuel lines, and the plugs cleaned up and gapped. I also had to replace the engine wiring harness due to an unbelievable amount of corrosion. Thought I could cut back a couple wires and splice into them, but the more tape I took off, the more corrosion I found in all wires . I'm glad it didn't start right up when I first tried - that thing was just waiting for a short induced fire! The other wiring seems to be okay.
 

Daviet

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Sep 24, 2008
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Re: '78 55hp ignition troubleshooting

I think I understand your thought process, If all you did was swap coil leads and got spark, I would think you have a bad power pack. I am sure someone with more experience will come along with some advice.
 

VaBlue

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Aug 25, 2009
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Re: '78 55hp ignition troubleshooting

Wow! This board gets a lot of threads!

The power pack seems obvious to me, but I can't get my head past the open between the leads and the armature plate (where the manual says there should be resistance). So I went out and purchased the necessary utensils to pull off the flywheel and look over the plate wiring. If it comes off easily, great! If not, I'll go get a power pack from a dealer and try my luck.
 
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