Ignition - Spark Into Distributor, Nothing Out!? CDI Coil Shorting Out?

79 Silverline

Seaman Apprentice
Joined
Jul 11, 2005
Messages
32
You guys are probably so tired of my questions, but you guys are my last hope in this nightmare series of events that's been going on. I took the boat out today and got all the ignition timing dialed in perfect. This is again on a 79 inline 6 90 HP. So we were out cruising around for a couple hours and everything is running better than I've ever seen it run before - it has a new trigger, new switchbox and coil combo from CDI. So we're boating around and then engine loses power and dies within a second or two. Had to be towed in. It started up a time or two, but would quickly die. Timing light showed badly missing spark. So much for the brand new ignition.<br /><br />It turns out that the trigger and switchbox are working, but spark is not getting past the distributor! If I directly connect the coil to a sparkplug, it'll fire all day long, no problems. However, I just can't get it to fire a plug through the distributor. When I test the spark from the coil, it'll only jump about 1/8th inch or so. This is a CDI coil that comes with the switchbox (114-2986). Is my brand new coil shorting out internally? I've already sent the box in for a warranty repair once, so I don't think they want to deal with me again.<br /><br />The cap and rotor on the otherhand appear to be alright - the cap doesn't look eroded away any significan amount, and the rotor doesn't appear to be either. Cap has no cracks or other damage. Brush going to the rotor is fine and the spring moves freely. What could be wrong?<br /><br /><Rant> I'm on a college student budget, and I've gone through two switchboxes and a trigger so far. I cooked the original switchbox when I was tired and connected the battery backwards. It's replacement got fried when I mixed up the trigger and 12V key wires late at night when I was trying to find a problem with the trigger - CDI warrantied it and that's what I have in the boat now. The accident which cooked the box also finished off the trigger, which I already suspected was bad. And now, I think the onboard coil on this latest CDI unit is dead due to no fault of my own and I'm all out of credibility with CDI. I've spent more on the boat than I bought it for, and no longer know what to do with it. It just left me hanging in time for a trip this weekend to top it all off. Anyways, I figure I'd share for your guys amusement. I don't believe in curses, but I'm beginning to...</rant>
 

Laddies

Banned
Joined
Sep 10, 2004
Messages
12,218
Re: Ignition - Spark Into Distributor, Nothing Out!? CDI Coil Shorting Out?

ck the rotor to see if its shorted to ground
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,036
Re: Ignition - Spark Into Distributor, Nothing Out!? CDI Coil Shorting Out?

It may be a grounding issue (long shot I think) Check to make sure the distributor body is grounded to the block with a wire, and that the cylinder head cover is grounded to the lower cowl and the lower cowl is grounded to the midsection, all with ground wires. Check the dist. cap for carbon traces, and that the carbon electrode in the cap is good.
 

Clams Canino

Commander
Joined
Jan 10, 2004
Messages
2,179
Re: Ignition - Spark Into Distributor, Nothing Out!? CDI Coil Shorting Out?

Carbon electrode is 1st suspect.<br /><br />-W
 

79 Silverline

Seaman Apprentice
Joined
Jul 11, 2005
Messages
32
Re: Ignition - Spark Into Distributor, Nothing Out!? CDI Coil Shorting Out?

I'd like to appologize for my rant above - the boat broke down 2 days before a big trip to Lake shasta, so I was a little pissed.<br /><br /> I did end up finding out what happened, and getting it patched up for the trip, but have discovered something I find alarming when it failed again the same way. I found out what happened. It turns out that my ignition coil (onboard the CDI switchbox/coil combo) fried. It'd make spark, but it became too weak to jump the combined gaps in the distributor and the plugs, and simply shorted internally. No fire, no go.<br /><br />I talked to CDI and they said about 1 in 200 (!!) fail, and they'd mail me another coil. They also said that an OMC coil would work - and sure enough, I went to the OMC shop in town and bought what looked to be an identical piece to the CDI part - worked like a charm and got it going. However, after putting a couple hours of runtime out on the lake with some higher RPM cruising, the coil fried AGAIN! I bought a spare just for that reason, and sure enough it was the coil. I did drive it onto the trailer under it's own power, but I figure it's a matter of time till I burn another coil out.<br /><br />Here's the deal - the ignition coil on the CDI unit is an OMC/Evinrude/Johnson "coil per cylinder" type coil. I don't honestly think it's designed to fire 6 times as many cylinders, and when asked to do so, it overheats and/or the insulation on the secondary winding allows internal shorting! Is there anything I can do to stop this problem? Closing the gaps in the distributor or something maybe? I'm going to post mortem my dead coil(s) and see how they failed.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,036
Re: Ignition - Spark Into Distributor, Nothing Out!? CDI Coil Shorting Out?

Is there a reason not to use Sierra brand aftermarket switchboxes, or used Mercury OEM switchboxes and standard coils? My Merc switchbox/coil is original on my '77 Merc.
 

Clams Canino

Commander
Joined
Jan 10, 2004
Messages
2,179
Re: Ignition - Spark Into Distributor, Nothing Out!? CDI Coil Shorting Out?

Yes there's a reason..... read the very post above yours for that reason.<br /><br />-W
 

79 Silverline

Seaman Apprentice
Joined
Jul 11, 2005
Messages
32
Re: Ignition - Spark Into Distributor, Nothing Out!? CDI Coil Shorting Out?

Alrighty, can anybody suggest anything that might create extra load on the coil? I'm thinking along the lines of high charging voltage, gap in the distributor is getting wide causing spark voltage to increase (breaking down the insulation in the secondary coil), etc.<br /><br />So far, my I6 has devoured a 2 day old CDI coil, and a used but tested good Evinrude coil. Odd part was that they died after almost the exact same amount of run time and mix of RPM useage. I don't believe in coincidences and I'm outta spares. Any ideas?<br /><br />Still looking for any input from I6 CDI ignition users (2986 type) - I'll feel better (and become more puzzled) if somebody tells me that they go banging around at WOT all day with theirs. Hey Clams, have you run this system any? I'd be grateful for any unput you have, since I figure you've probably seen it all. Thanks again guys.
 

clacka2.5xs

Recruit
Joined
Oct 25, 2014
Messages
1
that same coil fired OMC battery ignition systems on 6 cyl firing all 6 cyl as well so safe to say you may have a grounding issue causing voltage drop below 9.5 V to CD box and less than 9V to coil... thats how ours failed after another Co rewired the boat with to small of battery cable from engine,,,
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,589
Please read above guideline as this post is nearly 10 years old!!!!!!!!!
 
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