no fire on top cyl 4hp 1971 evinrude

[crosbyman]

ok ..going nowhere for some reason

points clean 0 ohms across , coils (modern) 4.6Kohms secondary …up to plug boot , primaries around 0 ohms condenser new.. metallic core wires (new) mag plate ground clip installed

bottom cyl fires ok same set up top cyl… dead 🙁

any hints ? before I start replacing things… like the top coil ?

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[Mumbles]

Try switching your spark plugs around and see what happens.

[dave-bernard]

before buying parts, replace by switching parts from top to bottom one at a time. condenser first then the coil just me.

[need2fish]

And then swap the capacitors. It gets a little uglier after that: swap the coils (check for cracks in them as you go), then swap the sparkplug leads..

When the problem follows the component, you’ve found the problem.

[crosbyman]

mumbles… I am using the same sparkplug and it fires ok on the bottom not on top

Dave… condensers …new same issue

swapping will begin tomorrow 🙁

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[dave-bernard]

new condensers are not always good. try it first easiest to do.
Do the John Cash Cadilac song one piece at a time .

• This reply was modified 4 years, 9 months ago by dave-bernard.

[crosbyman]

new coil with the screw HV connection new set of points new condenser tested good on H.Mowhat box 6.9Kohms secondary 1.9 ohms primary cct boot to engine frame 6.9Kohms

boot to primaries 6.9Kohms each infinity (open) between primaries, secondary Hv to laminates (no internal grounding)

this not something I haven’t done before on several oldies

result: NO FIRE on top plug 🙁 🙁

my only option 🙁 swing all the bottom cyl. electricals to the top cyl. position retry

crows are circling or murphy is at the door

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[dave-bernard]

Do then switch one piece at a time.

[Mumbles]

Just because the plug wires give you an ohm reading doesn’t mean they can carry enough current to fire the plug. The spring connector inside the plug boot might be loose or corroded giving a false impression everything is OK when it isn’t.

[fleetwin]

Not really understanding your technical abbreviations…But, like Mumbles says, just cuz the wires seem to test OK doesn’t mean they aren’t shorted or partially open. The plug wire routing on these 4hp models is relatively tight, and the wires tend to get caught up in the cover latch. I guess I would swap the components one at a time, starting with the easiest swap, which is probably the condensers, then the coils, then the points…Ya better mark the pieces so you don’t get confused. The plug wires are relatively difficult to replace/swap…So, once all the other components have been ruled out, I would buy new wires and just replace them. Again, be very careful routing the wires near the cylinder head through the clamp, they get caught in the cover latch and get ruined easily..

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