I am only getting spark in one cylinder on my 1987 Mercury…

Okay start with this. Swap the firing coil for a non firing coil. And let me know if the coil that sparks still sparks when you move it to another cylinder, or if it stops firing when you move it to another cylinder.

Okay next, locate the main harness plug, this is a big round plug. Disconnect the plug. Then, go over to the starter solenoid and jump the yellow/red wire to power, this will crank the engine over. Let me know if spark returns when the harness's are disconnected.

You said you replaced the stator trigger and switchbox. Are you using new mercury parts, new aftermarket parts, or used parts?

The stator and trigger are testable with a volt ohm meter. Do you have a digital, preferably auto ranging, volt/ohm meter? And do you know how to take resistance measurements?

Do you have a digital, preferably auto ranging, volt/ohm meter? And do you know how to take resistance measurements?

Bascially you either have bad ignition components, a bad flywheel, or a bad harness. The stator and trigger need to be checked with a multimeter, the flywheel needs to be checked with a hack saw blade or something similar. Do you have these tools?

On the stator. disconnect blue and red from the switchbox, and measure between blue and red and let me know what you get for a reading.

On the trigger, measure between brown and white/black, white and white/black, and purple and white black, and let me know what you get there.

On the flywheel, pull the flywheel and use something like a hack saw blade and hold it against the magnets and see if the magnets pull hard on the blade. Also do the same thing on the inner hub of the flywheel as well.

Let me know how you make out.

Okay these numbers. Is your meter auto ranging or manual ranging? For example, on the stators blue and read wires, is that 610 ohms or 6100 ohms? On your trigger, the first one, is that .891 ohm (under 1 ohm) or is that really 891 ohms?

Is the stator a mercury part or a CDI/aftermarket part?

Does your stator also have blue/white and red/white wires in addition to the blue and red? Or is there just a blue and red?

Do this. On the bottom of your switch box there are 4 terminals. On the left most terminal hook up the blue wire. On the next terminal over to the right, hook up the blue/white. Hook all your trigger wires back up. Let me know if spark returns or if it does the same thing.

You have blue and blue/white hooked up to the switchbox on the left two terminals correct?

At this point we have taken this as far as we can without a DVA. A DVA is an adaptor that allows your meter to read outboard voltages. Can you get a DVA and get back to me? (you can order them from CDI or snap on)

Okay lets do that. Doing the resistance tests that we have been doing is sort of winging it, which is all we can do if you don't have a DVA. With a DVA we can do it by the book, and definitely zero in on specifically what the problem is. Just reply back once you have the tool an we will take it from there. Have a good night. -Jason

Okay i'll catch ya later.

Hello, just checking in, Did you ever get that DVA?