spark help from coil from a 4 cylinder merc

[alan ber]

I have a starting issue.
Right now it does not work.
I have a 1984 4 cylinder mercruiser engine.
During past few weeks at times not getting power too turn engine over.
Cranks, getting fuel, won't start.
Mess with electrical harness, and starts
Works 4 weeks, then craps out.
Today it's cranking away won't start.
Not sure if it's within the electrical harness or wiring from harness too distributor, coil
Just changed points, and I am getting power, see spark from breaker
Don't do this enough and need some advice.
WHen I turn key switch on I get power from both legs of coil.
I put test light on spark plug wire no flicker of test light. By passing coil plug wire put tester end into coil cavity, cranking engine tester light does not flicker, had a back up coil, installed did the same .
My question is when key is on power should there be power on both sides of coil?
Under normal conditions when cranking engine, is there enough power going thru coil too make tester flicker too indicate
some sort of juice ?


Little confused on how power goes around,

I am thinking both coils are n.g.
Before I run too parts house want too test , how do one test a coil?

thanks

 

[Eric 3.7LX Alpha 1]

Re: spark help from coil from a 4 cylinder merc

You test an ignition coil by checking the resistance with an ohm meter between (+) and (-) terminals on the coil called the "primary" and also (+) terminals to the center post where the plug wire attaches called the "secondary"

the reading is suppose to be within a range or the coil is NG

Read both of these:

How To: Troubleshoot a Points Ignition System
http://forums.iboats.com/showthread.php?t=335407

and also this

How points ignition system works.
http://forums.iboats.com/showthread.php?t=329742&p=2186518#post2186518


both from the sticky at the beginning of this forum
What engine is in there?