juice to the coils but not to plug-25hp 1975 evinrude

[Hiawatha]

can mice messy coils be cleaned up? i have juice to the coils but not to the plug, i ordered 2 new ones but if i can save old ones for back up i will

thanks again
dave

[fleetwin]

Well, the one thing I have learned about those external coils is that a lousy looking exterior does not necessarily mean they are NFG. Needless to say, without seeing what the mice did to your coils it is hard to say if they are worth keeping….But, I would surely keep them for possible back up, you have already ordered new ones…
I’m just wondering about your explanation "..I have juice to the coils, but not the plug…." diagnosis….How did you test this? If your diagnosis is in fact correct, that would probably indicate that both of your coils are inoperative.
There are some resistance tests for these coils, but you would also need to test on the stevens/Mercotronic tester to confirm having good coils with no external leakage. In other words, just because the resistance tests come out within range does not mean the coils are good. But, if the resistance tests are way out of range, that does mean the coils are NFG.
Did you try unplugging the two stop leads and testing for spark?

[Hiawatha]

"I have juice to the coils, but not the plug…."
there is a plug just before each coil, i unplugged each one and turned over motor using test light, test light lit up bright

i believe the plug wire coming out of the coil could be cleaned and i bet they would work, plugs were also terribly rusted, mouse pee really leaves a white crusty mess

[ken-w]

Is this a Low tension system? If so yo can use a DVM (digital volt meter) with a DVA to read the input voltage of 60V.

kw

[vintin]

Maybe the spark plug wires are not making good contact where they connect to the coils.

[fleetwin]

Well, lighting a test light while cranking/testing the primary leads is not an real accurate test, just shows that something is coming out from under the flywheel….You will know soon enough when you install the new coils…Make sure to ground them well and that the engine end of the primary connections has not been rusted/corroded due to mouse pee….

[crosbyman]

back to square one….

have you tried cleaning up all… connections points

ex: removing the coils and making certain all grounds are clean etc….

did you measure the coil primary and secondary windings to a good… scrapped ground reference

2 coils bad simultaneously is pretty bad luck

please publish test results fore all of us

Joining AOMCI has priviledges 🙂

[outbdnut2]

On your motor, if either set of points is not functioning right, it will kill spark to both cylinders. The only way to see if enough voltage is coming out of the Driver coil/points circuit is a "sample and hold" meter, or a storage oscilloscope.
Dave

[rudderless]

High point resistance might give optimistic results at the feed plug but might not flow enough current when connected to the coil. Probably using a 20,000 ohm tester or so. Leave the coil connected and then test voltage to the primary.

I have used a 12 volt battery charger to halfass test coils. Ground the black clip to the coil and scratch the coil hot wire over the red clip. Use a good plug grounded to the black clip, secondary connected. A good coil has always sparked this way for me and a bad coil never does.

[Author]

Posts