86 mercruiser 120HP no spark

[matt_rad73]

Ok I have tested and retested this problem. Everything for the adutls only troubleshooting ingintion thread. Coil, rotar and cap have been replaced points look like new. If I use a spark tester from the coil to ground, At the moment the key is turned to start there is a small spark and then for as long as you crank the motor no sparks. As soon as you stop cranking the motor a very weak spark is noticed also.

Any ideas?

Matt

 

[TowRoper]

Re: 86 mercruiser 120HP no spark

try disconnecting the gray tach wire and try again i had the same thing and it was that my tach was DOA its just an idea cuz its a free test and an easy one lol

 

[bruceb58]

Re: 86 mercruiser 120HP no spark

Check the voltage at the positive side of the coil and verify you have 12V with the key on and the points open. With the points closed, it will drop a few volts if you have an external ballast resisitor. At the negative side of the coil, you should have 12V with the point open and 0V with the points closed.

Manually open and close the points with your spark tester atached to the coil. You should be getting a big spark when you open the points.