"I am not getting spark on half of my cylinders.
a. When I originally discoverd the problem I switched the power packs. The problem moved w/ the power packs so I thought great I know what it is. I bought a USED power pack locally.
b. Installed used power pack. Same problem still exists..no spark on one side..will move with power pack. I assume used power pack is bad. Shop has another one. I take it home....same indications..now I'm really scratching my head. Only one thing to do now.
c. I buy a NEW power pack. Guess what...same problem. Whatever side the NEW power pack is on is where I don't get spark.
d. I have removed the black/yellow kill wires..it still starts with them removed.
e. I spoke to a tech at CDI electronics...they say I should buy an additional power pack and that they always recommend replacing both (convenient for someone who sells power packs). My local mechanics says he's heard it recommended but never required.
d. I removed my known good power pack and only left the new one on to just test it by itself to try to prove/disprove CDI's theory. It gets no spark with only the new power pack installed.
e. Most people I have talked to have told me to start trouble shooting the stator, but haven't I proved both sides of the electical system good by switching my power packs and being able to get spark on either side depending on where the non-new pack is?
I think this is a doozy of a problem because it just doesn't make sense. I am in the Navy and work with electronic weapons systems and everything that I've learned says if you switch a component and the problem moves then that is a faulty component.....that doesn't seem to ring true here.
Please help! My boat is not near as much fun when its sitting in my driveway...Thanks, Shane Burris"
"A. That switch component theroy does not always work in Mercland. Or some other CD systems.
B. One thing you need to understand about CD Ign sysems is that there is a stop diode in each Switchbox or CD pack. Which means in english that the pack that IS throwing the spark will turn out to be the broken one in a multi-pack system. This is because all of the blk/yel stop leads are spliced together in the harness and the packs need to be diode isolated correcely from each other on the stop circuit. The pack with the bad diode will kill the others and keep on working on it's own outputs.
C. The "black stator" the Merc used was known for going bad. There are two sets of winding's creating a hi-lo split system. The transition occures at ~2000RPM. Blue is lo-speed, red is hi-speed. If the blue winding fails you will loose 3 cylinders (1 bank) immediately. If the hi-speed fails the engine will non run over 2000RPM but will sit there and idle on all 6. It will drop that bank at the transition speed or break up and run so badly it wont get on plane.
D. When the stator fails the hi-speed it can and will spike the boxes and damage them.
E. If either box is damaged (shorted) it may kill the other if only one is replaced resulting in an endless circle jerk of replacing boxes. A bad stator will do this as well.
F. The bias portion of the CD system is what stabilzes the timing of the two ign. systems and locks then together. This also imposes a negaitve voltage against the trigger voltage to keep it stable against the normal voltage up-slope as the engine accelerates. That is the part of the system that Merc became imfamous for. (Blowing up V-6's) This is the portion of the box that can not be accuratly checked. Maybe dynamicly with the timing light, but that is a huge crapshoot that will lead to a blown pision if you are wrong. The 2 stroke motor cannot handle the additonal spark advance. There is a capacitor & didoe in the box for each cylinder's timing. That is the part that cannot be tested.
G. The idle stabilizer module will case similar symptoms of a hi-speed failure. This can be safely removed it does not have a high speed retard function in it. Some did. This needs to be unplugged to set the timing & linkage on the light.
H. There is no logic control in the switch box. The SRC is activatied by the trigger voltage on the base of the transistor. Hence determining the timing. (again ,rising voltage will advance) This will shift as the sw box ages. Eventually leading to a blown piston somewhere.
"I'm gonna test the voltages on the stator tomorrow.
Are you suggesting that I put in an additional switch box? I have the one that I took out of the sytem (thinking it was bad.) Should I put it back in with the new one and see what it does? It does have a broken post that I broke taking it off because it was so corroded. This post would only fault the middle cylinder on either side though, I believe. So I should be able to troubleshoot with it.
I was informed of the high speed/low speed windings..although I'm not sure I totally grasp how it works. Your description clears it up alot.
With what your describing I think the blue has failed because I lost 3 cylinders and it won't get on a plane. It acts as a trolling motor really.
So...where should I go from here? Besides testing the stator..what other modes of attack are there? Also, what are the chances that I've ruined this new switch box?
Thanks for your post and I'm standing by."
I would normally would not hesitate to replace both boxes and the stator when anything goes wrong with this system. That is my S.O.P. I think it is the best way to attack these. And stay out of trouble. And dissconnect the stablizer during the prosess. The hi- and low speed windings eliminated the need for and additional voltage regulator to protect the switch-box as well as gererate enough power to work at cranking speed. The lo puts out full voltage at a very low RPM to get started and the hi-speed is wound to put out full voltage at higher RPM. 180V at 1000RPM vs. 180V at 5500RPM.
"Alright, got it. What about the trigger? Is it not suspect also? I don't think at idle speeds it has anything to do but with my limited knowledge I thought I better ask.
I'm having a hard time finding the stabilizer. Where is it located. I can see it on the wiring diagrams....and actually there is a black/white wire that comes off of one of my boxes that is spliced and doesn't go anywhere. According to my shop manual that should go to the stabilizer..any hints?"
Bandit-
I did resistance checks on the stator and trigger in accordance with the shop manual. The checks are all good. Are resistance checks thorough enough to rule out a bad stator? Or is the only way to do the voltage checks while cranking?
I am going to take the pack that I "think" is good (its now suspect based on your statement that the one that is firing is often the bad one) out of the system and use the new one and the one I originally thought was bad (not firing) and see what I get. I'm not sure what I have to lose at this point.
Thanks in advance for your help.
Alright...I got it fixed. The quick down and dirty is that the wires coming from the Port and Stbd power packs were swithed. So the port pack was sending fire to the stbd side and vice versa. So I had a bad pack in the system this whole time but kept thinking the opposite side was not firing.
I took the new pack and the one that I thought was bad and put them on. It fired up and had spark on all cylinders...with one exception. The presumed bad pack has a lead broke off of it that I broke of while removing it. That lead would not send spark to the lower cylinder on whichever side it is on. When I was checking spark I noticed that the missing spark was not where I thought it would be...so I start tracing wiring and low and behold the wires are crossed.
That gives a very simple explanation to a seemingly crazy problem.....I'm kinda kicking myself for making the assumption it was wired the way it should be but oh well...if fixed now and I'll be in the water tomorrow!
One more question though..the black/white lead and red lead that come off my stbd pack that are spliced should go to an "advance module" according to my shop manual. This is not there and has never been there when I've ran it prior. I know it seems to run fine without it but is this something I should look into putting back on?
Thanks for all your help and patience and to all reading this...when the problem gets really hairy and don't seem to make sense CHECK TO MAKE SURE THE WIRING IT GOING WHERE YOU THINK IT IS!
Thats O.K. This is not always an easy system except to say that that there is a pattern to its failures as far as stators and triggers go. It gets harder when someone else works on it first. I forgot to mention that the yellow sleeves on some of the wiring indicates where things go. If that gets crossed up things will get weird.
As far as the "advance module" leads go You did not state "what" they were spliced into. There should be no splicing. Either that module is there or it in not.
That idle speed control module does not need to be there. I usually do not bother to replace it. It was used as a shift/idle assist for a very big wheel.(prop)
It might help to remove any rouge wiring and just leave the black/white jumper wire in place between the boxes.
I shouldn't have used the word spliced...they are cut off and not attached to anything. I have seen a problem in my boat when I'm waiting inline to dock..and I'm jockeying the throttle back and forth to position keep....when I'm doing that sometimes the engine will die..it starts right back up though...could this be due to the lack of that module?
