Mercury 900 no spark

[DanWalker223]

Hi guys. Trying to get my tower of power running again. I'm getting spark to the distributor but nothing is coming out. Is there a way to test the rotor button before I just throw more money at it and buy a new one? I'm pretty stumped. I put new plug wires and a new coil on it, thinking that was my issue, but now, like I said, I'm getting spark to distributor, but nothing coming out. Could the spring and brush be an issue? What should I be looking for on them? Hoping this is a cheap fix, and there is just some small common issue that I need to address. As a side note, I'm only getting 9.5 volts on the red wire on the engine switch panel when the motor is being cranked. Is that an issue? White wire below it has 12V with the key on.

 

[Chris1956]

Voltage on the red wire should be +12VDC. It is a direct connection to the battery. It sounds like you need to clean those connections. Is the engine wiring harness still good? Most are losing their insulation by now.

Cap electrode and spring are maintenance items. Cap and rotor are not. As long as the rotor is not broken, it should be fine. Replace the electrode and spring if it looks overly worn. They last a real long time.

You did use mercury-style spark plug wires when you replaced them? The spark plug wires have solid, stranded stainless steel conductors. Resistance on them is zero. You might check it.

At this point in it's life, the triggers can get intermittent. However, if you have spark out of the coil, the trigger is working.

So you have spark into the cap but not out. Perhaps the distributor is out of time? If the rotor is pointing at the wrong cylinder or no cylinder when the spark happens, it will look like no spark out. The distributor cap only fits one way correctly, but can be put on wrong, easily. Make sure to match the notches in the cap with the notch in the distributor body.

Check the timing mark on the distributor pulley, against the mark on the timing decal on the flywheel. They need to match. They could be off by 1/2 tooth, which is OK.

 

[DanWalker223]

Checked timing and hooked up a spark plug tester. No spark at plugs, and now no spark at coil. How do I test my trigger? Is that the next most likely culprit?

 

[Chris1956]

There is an ignition test for those motors at the CDI Electronics web site. It assumes the coil is good, and tests the battery-powered CDI switchbox and wiring. It does not test the trigger, but tests all other components. I suggest you run this test.

If no spark during test, the switchbox is bad or the wiring is bad. If spark during the test and not after the test, the trigger is likely bad.

 

[DanWalker223]

There is an ignition test for those motors at the CDI Electronics web site. It assumes the coil is good, and tests the battery-powered CDI switchbox and wiring. It does not test the trigger, but tests all other components. I suggest you run this test.

If no spark during test, the switchbox is bad or the wiring is bad. If spark during the test and not after the test, the trigger is likely bad.

I went to the site but couldn't find it. Could you post a link for it please? Sorry, I'm not the best when it comes to the internet.

 

[Faztbullet]

 

[DanWalker223]

View attachment 384283

THANKS!!!