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No spark from switch box power pack to the coil

R

Rlindsey

New member
I’ve replaced every electrical part on this 1978 mercury 150 hp black max getting plenty of fire to switch boxes but just a very little spark coming out going to my coils but it’s enough to show a weak spark at spark plug end of wires !! Somebody please tell me what’s wrong my wife’s ready to kick me to the shed if I keep spending money on this motor !!! Lol
 
You need to buy, beg or borrow a DVA meter and see what voltage is going on. The truth will jump right out at you, and at cranking revs. Great tool.

I bought an adapter for my regular volt-amp-ohm meter on Amazon and it works great.

Jeff
 
Sounds like bad or wrong stator....the 1978 use a fine tooth flywheel and what is the lamination thickness??
 
Maybe the flywheel is demagnetized. See if it will hold your wife's earings. Ok then, only kidding. Should pick up a decent size screwdriver.
 
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build your own dva adapter, costs like $2, INVALUABLE in troubleshooting! Theres NO OTHER WAY. Its a tiny diode, capacitor and 1 or 2 resistors.

From there get your AC readings, write them down color for color, also - do this at varying rpms. Took me a while but finally got the hang of it.

You can also disconnect your safety kill wire from the packs in case u have a faulty connection there. a bad reg/rect can also cause problems.

Dont always assume plug wires are good.. take them apart, snip a tiny piece off each end and re-assemble.. always good to get good new solid core wires..

You usually start from the stator - it feeds EVERYTHING. The wires going into the switch boxes need to be tested.. You can ground the ignition, remove plugs for a fast spin on starter to get some readings while cranking (assuming she isnt running)..

cdi has some real good specs in their documentation for OEM and aftermarket (cdi) parts..
 
..."A dva adapter ...(is)...INVALUABLE in troubleshooting!!"

Couldn't agree more. I bought an "Electronics Specialties 640 DSVA Adapter" on Amazon for my meter and it works slick!

Jeff
 
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