Why two bad CD modules?

[activa]

'87 Force 85--I have tested and believe I have confirmed that both of the ignition modules are bad--on the front one, the orange output, and on the rear one, the red output. I'm wondering if there is something connecting the two that is either making them act bad or something that burned them both out.

This page: http://outboardparts.com/troubleshooting/printguide.htm states:

"NO FIRE OR INTERMITTENT ON ONE CYLINDER:
Check stator and trigger resistance. If readings are good, disconnect kill wire from all packs. If the dead cylinder starts firing, the problem is likely the blocking diode in one of the other packs.

which I did, but still no luck. Anyone have any ideas? Or is it possible that both modules went bad together?

Thanks.

 

[chuckz]

Re: Why two bad CD modules?

Only one output is used on the forward module. There is not trigger for it because the 85 is a 3 cylinder engine. Swap the two modules and see if spark returns to #1 and #2. Depending on which output was initially bad in the aft module, #3 may or may not fire. If you can understand the wiring, you can swap input on the module firing #3 to get to the good half.

 

[Frank Acampora]

Re: Why two bad CD modules?

The white wire is the kill wire and each one from each CD unit is connected to the same terminal. The blocking diode prevents feedback through the two white wires. SO: if the blocking diode in the other cd unit is bad, it will short the first cd unit to ground thus killing the ignition on the first pack. In this scenario, the first cd pack may be good but the second cd unit is making it appear non-functional.

 

[QuadManiac]

Re: Why two bad CD modules?

Frank, so will just disconnecting the bad unit's white wire at the terminal eliminate the problem?

Also, is the bad blocking diode shorted? Is it accessible or potted inside? If shorted and inaccessible, wont just adding an external diode to it's white wire (in the correct direction, of course) isolate the signal again? (just about any 1N400X series should handle the voltage). Sounds like a nice, easy, cheap ($3 at Radio Shack for 25) solution?

 

[activa]

Re: Why two bad CD modules?

Hi, glad to get some action on this, it has me stumped. I believe I've confirmed that everything else (stator, trigger, coils and wires) are working, and that only the red output of the front pack and the orange output of the rear pack are working. I pulled both kill wires from the packs, but that didn't help.

The magneto outputs ac, and the packs have to rectify the ac to charge the caps. Instead of a full-wave rectifier, do the diodes in each pack simply split the wave sending half one way to a cap for the red output and half the other way for the orange?

If this is the case, and if one of these diodes is shorted, and since the blue stator outputs are tied together on the block, is it possible that half the ac waveform from both sides of the stator isn't getting through, and so one of the outputs on each pack isn't getting charged?

Can I test for this by separating the stator outputs somehow? Will it damage the stator windings to run it without a load?

PS This site: http://standardmagneto.com/Marine/forceparts.html has really good prices on ignition parts. Anybody ever order from them?

 

[JDP]

Re: Why two bad CD modules?

I started to order from standard magneto but they didn't have the CD I needed and said it would take 2-3 weeks to get one. If you need the 116-5301 then You will have to wait a while if you order from them. I didn't want to wait so I paid a little bit more.

 

[Frank Acampora]

Re: Why two bad CD modules?

The electronics are getting a little heavy for me. However, this much I do know: on the three cylinder engines, the two blue wires are tied together on the terminal because the stator is AC. One yellow and blue pair charge one CD unit and the other yellow charges the single cylinder unit. Since it is an AC system, both wires of each pair are carrying AC current. The current must have somewhere to go so they tie the unused blue into the other. I do not know if the current is rectified to charge the capacitors. I do know that they do not use both polarities of the AC to charge different capacitors because:

The old Magna Power II which was extremely unreliable used both halves of the AC current to charge different capacitors so one set of plugs fired positive and one set fired negative. The system was so bad they only used it in several engines for about three years. They learned their lesson with that one.

 

[activa]

Re: Why two bad CD modules?

Thanks for the input. I ordered a module from standardmagneto.com, they said I could return the module if it didn't fix the problem (as long, obviously, as whatever killed the supposedly bad module doesn't kill the new one) which I thought was mighty generous of them, plus their price was half of anybody else's, and literally about 1/5 of what the local dealer wanted. The later modules were not in stock--they actually fabricate them there--but mine was, so it's coming UPS ground. I'll post the results when I stick the new one in.

 

[4runneradam]

Re: Why two bad CD modules?

So you definitely ruled out the stator? Did you check resistance on it? Wiggle the wires around while doing so?

I thought I had a bad module, turned out the stator had a short in it when you would wiggle the wires a bit.

 

[activa]

Re: Why two bad CD modules?

Ok, I woke up at 5:30 this morning when a light went off (in my head)--yes, there are two outputs on each module, but the stator output isn't connected to the fourth output--the red output on the rear module! No wonder it wouldn't work!

So I swapped the front and rear module magneto inputs, and then swapped the yellow and blue inputs from the front magneto and PRESTO! spark on all three cylinders!

There are several posts in this forum noting that the rear module in this system is not used and can be used if one of the other outputs is bad. This is correct--BUT YOU HAVE TO SWAP THE MAGNETO INPUTS TO GET IT TO WORK!

I expect you're all saying "DUH! isn't that obvious!" It wasn't to me, and so for anybody else who ever has this problem--BE AWARE!

Thanks again to those who helped me out.

 

[MikDee]

Re: Why two bad CD modules?

Well, Good Thinkin! I couldn't see the forrest from the tree's either, but glad you got it! something for us all to remember to check.

 

[chuckz]

Re: Why two bad CD modules?

Reread my post to you. I said swap the two modules, meeting physically replace one with the other. Then the triggers and stators are all connected properly.

 

[activa]

Re: Why two bad CD modules?

Reread my post to you. I said swap the two modules, meeting physically replace one with the other. Then the triggers and stators are all connected properly.

Well... almost but not quite--physically swapping them exactly would place the trigger for cyl #3 on the input that was bad. What I did was move the inputs around so that this input didn't get a stator output.