3.0 Digital Distributorless Ignition System (DDIS) probs

[BF]

Hi all, long time, no post.

I've got a rough idle, lack of power on my 3.0 Mercruiser with the digital distributorless ignition (1990 searay). I have the factory service manual but can't find any diagram about where the appropriate ignition wire goes. With a cap you can go by the firing order around the cap, but with the digital thing, it wouldn't necessarily go in a circle like that (?). I just want to make sure that 2 wires didn't get switched along the way (I've seen that before), and want to troubleshoot the ignition system. Probably replace the wires since they're original (although seem OK).

I've attached a pict of where the wires are now on the module, but I don't think the cyl # is marked on the ignition module (of which wire should go where) (?). You can see the boot of plug 4, and almost see #3, then #2 is the wire closest to the block, #1, is the one on the outside running the farthest.

Thoughts?

Thx.

 

[Bt Doctur]

 

[BF]

Awesome! Many thanks... from that I can tell that my wires are correctly connected. I'll keep a copy of that pict to supplement my manual. A followup Q if you don't mind... I was just at a friend's place who bought a '93 3.0L that also has the digital ignition, but his has a cap. (?) Was the module above (and what mine has) a very short lived component that only was used a couple years? Did this ignition system have any particular problems, or things that I should watch for?

Many thanks again...

 

[CFM56-7]

I bought a boat equipped with the DDIS ignition system late last year and all the research I've done seems to indicate it was used for a span of just a few years. In theory, an all solid state ignition setup seems like a great way to go. I'm not sure why it wasn't more widely adopted, but now parts are difficult to find and prohibitively expensive if you do.

My DDIS system was on the way out when I took possession of the boat and it would no longer maintain proper timing. The solid state design made it unserviceable and I couldn't find replacement parts. Luckily, with just a little modification, the Delco EST ignition system is a fairly inexpensive, almost drop in replacement for the DDIS system. A complete kit can be purchased for $259 which includes a new distributor, coil. wires and everything else needed for the conversion.

After I installed the new ignition system and got her properly timed, it was much easier to start and my idle became very solid. If you can confirm your ignition system is the culprit, the Delco EST ignition system swap is the way to go.

CFM

 

[BF]

Thanks for the additional info. The factory service manual I have seems to cover several years of the 3.0 and doesn't have much in it about diagnostics for this ignition system (a couple of pretty generic flow charts). Did you have a manual or source that you found useful? Wherever that pict that Bt Doctur posted came from likely has diagnostic info in it.... I'll go through the adults only section and see if maybe there have been some updates in there since last time I browsed it... Funny that you mention timing, b/c with how it's acting it feels like the timing could be off. I didn't have a light with me to check it, but then I realized that without a distributor, there doesn't seem to be any way to adjust it anyway (?).

My symptoms are rough idle, almost sound like it's missing... low on power and a noticeable bog at the bottom end, particularly when under a heavier load. Once on plane with the rpm's up, it runs well, but I think it's still down on power there too compared to how it was last season. Does this sound like how yours was when the ignition was failing? What mod's were needed to install the Delco system?

Thx for your help!

 

[CFM56-7]

Mercruise manual #13, pages 4B-13 through 4B-20 covers the DDIS ignition system as thoroughly as you'll ever need.

A timing light is critical and was the only way I could have verified that the timing was jumping around on me. In lieu of a distributor, the DDIS system uses a "Motion Sensor" that sits where the distributor normal would be located. Timing is measured off the #1 spark plug wire with the engine idling under 900 rpm's and set to 8 degrees BTDC. This is done by rotating the motion sensor just like you would normally rotate a distributor.

The problem you describe could just as easily be attributed to a fuel problem as well. My symptoms were basically rough start and inconsistent idle. I had a lot of other issues going on too though, one of which was low voltage to the ignition system which is probably what caused my DDIS system to fail in the first place.

The Delco EST conversion is basically removing the DDIS components and replacing them with the EST components. The wiring requires some modification, but if you can solder it's quite simple. If you get to that point, we'll make sure you get all the assistance you need.

Keep us posted!
CFM

 

[Bt Doctur]

http://www.boatfix.com/merc/Servmanl/13/13covr2.pdf

 

[BF]

Thanks for the additional info guys.... I'll do some reading and make sure I have my timing light and multimeter with me next time I get to the boat. The diagnostics in those manual pages are just what I needed.

 

[BF]

Hi again,

So I finally got to run through the DDIS diagnostics on my 3.0 this weekend. The coil is out of spec for the secondary resistance... manual says it should be 11.3 -15.5 Ohms, between towers 1 & 4 and also between 2 & 3.... Mine shows no continuity (infinite resistance) between those towers. When checking the timing, although the base timing looked to be spec at 8 degrees, there appeared (?) to be a significant amount of jitter/misfires on the timing light, which I think might be sporadic sparking that would contribute to the rough, sputtering idle. The ignition amplifier and motion sensor tested within spec.

Does a (partial?) coil failure seem to make sense with the symptoms I'm having? They are: rough idle, hard to start, lack of low end power and bog off the bottom. I ran the boat on the weekend and it was running progressively worse, definitely needs attention, so I pulled it home so I can wrench on it.

I'm going to see whether I can find a Delco EST kit locally, otherwise I'll order it online... Are the mod's to the wiring that CFM mentioned described in the Delco kit? Or does that kit come as just a box of parts, with no instructions on how to make the conversion?

Thanks for your $.02...

 

[CFM56-7]

BF,

I got mine from Michigan Motorz. The instructions included an excellent wiring diagram, but did not describe the specific changes necessary to complete the conversion. It is not necessarily sold as a conversion kit, but rather a replacement kit for the factory Delco EST ignition kit.

By comparing the wiring schematics in the manual, the changes needed are pretty obvious. If you are looking for specific guidance on what changes need to be made, I'd have to compare the wiring diagrams again and make out a list. If I remember correctly, 3 changes were made.

Happy to hear you were able to confirm part of your ignition system is problematic. At minimum it is contributing to your symptoms if not fully responsible.

CFM

 

[BF]

Well, before I ordered the complete EST kit, I got lucky and found a new old stock DDIS coil for <$200 incl shipping. With it being the exact part it's an easy R&R, and I might be able to get back on the water for this weekend (if it gets here). Hopefully the rest of the ignition components will survive for a few more years. If the amplifier or motion sensor croaks soon, I'll be kicking myself for not just converting to the EST system now. We'll see. I'll post an update once the part is replaced of whether it resolves all the issues or not...

Thx

 

[BF]

Hi again,

Just thought I'd post the epilogue to this story... Changed the suspect coil... while I was poking around I pulled the spark plugs.. 3 of the 4 looked good, but number 3 looked a bit sooty and oily... not awful, but different than the others that were nice and tan. So I put back one of the plugs that I had swapped out at the start of the season.. Also did a compression test to rule out stuck valve... all cyl were good and even.. Last thing was I pulled the fuel filter at the carb... had a few dots of dirt, but definitely wasn't the issue. Put a couple cans of seafoam into the 1/2 tank of gas anyway... Pulled the boat back out to the lake and am pleased to say it runs way better. Idle is even and starting is much better. No bog off the bottom. So I'm pretty sure the issue was the coil, that was likely only intermittently firing #3 plug. Used it 4 or so more hours of tubing/kneeboarding and it seemed to be running as good as ever... idle seems even smoother now, so maybe the seafoam helped a bit. So it was ~$160 for the coil plus $20 of seafoam, and it looks like all is good. Definitely was lucky to find a new old stock coil which appeared to be "unobtainium" locally. Even if someone had one, their retail price would've been ~$300 here...

So, thanks for the help that was offered in this thread. Next time I have some ignition failure, it will likely mean swapping out the DDIS to the EST system... we'll see.

Cheers!

 

[CFM56-7]

I love happy endings.... Glad it all worked out!