No spark on DDIS ignition, moving to wiring harness

[Thomasabbott91]

Gentlemen,

What a week it's been. I purchased a new ignition coil and amplifier for my 1989 3.0 l mercruiser, (they're not cheap), and still no spark. So I removed the wiring harness so see if there is a short or anything. Will a continuity test work to make sure they are fine, or does it need to be hooked up to a battery to really know?

 

[alldodge]

Sorry it appears no one has seen your two other post on the same subject including my self posted on July 22 and 25. Suggest if folks don't see it, just post again on the same thread with something like "Bump" and it will bring it back to the top.

In your other thread you asked about switching from DDIS to EST.
http://forums.iboats.com/forum/engin...dis-conversion

Figuring you have decided against it. Here is the wiring diagram for the DDIS for reference

Yes you can ring them out. After that you need to know if the components are getting power and have a good ground. In previous post you had problems with rusty motor and battery.

Since you bought the coil and module, the next thing would be to check the distributer, but before that go thru this troubleshooting sequence

This should also be in the Mercruiser section

 

[Thomasabbott91]

I got the harness hooked back up and followed the wiring diagram. Cranked it over, no spark. Tested the amp, nothing, tested 12 v (purple) wire at harness connector, got 0.2v. BUT, then got 12v on purple wire at alternator, and 10v at choke. I don't understand how that could be, unless it's as easy as a short, but I just did a continuity test and they all checked out. Could there be a short? Or bad ground? Any help would be great.

 

[alldodge]

No 12V at the amp or harness feeding amp. Have 12V at the ALT and 10V at the choke, but not a big issue if only 10V, but may be part of the issue. Full 12V at the ALT means you are getting power to the harness. All the purple wires are spliced together inside the harness, so you have a break in the connection.

I would either trace the purple wire back into the harness to find out where it's broke, or run a new wire from the ALT purple wire to the amp connector. Don't use the choke wire because it is a resistor. If you run a new wire, make a good connection, seal it tight and tape up the old wire so it doesn't ground out in the future

Edit: removed my comment about the resistance at the choke

 

[Thomasabbott91]

I will do it tonight and report back

 

[Thomasabbott91]

No Title

Actually I think it's the other way around, 12v at choke, 10 at alt. I'll double check when I get home but, but now that I remember it, I think that's it.

 

[alldodge]

Actually now that you mention it there should be no resistor wire, my bad, that would be with points ignition. In any case you should have 12V on all purple wires

 

[Thomasabbott91]

Ok, so I should find the connection point for all 3 wires, inspect, if I do not see anything, should I cut them, test, and solder and tape them, or just run new wiring?

 

[alldodge]

Ok, so I should find the connection point for all 3 wires, inspect, if I do not see anything, should I cut them, test, and solder and tape them, or just run new wiring?

That is up to you for use what you have or run new. It could be the issue is only with the wire feeding the module, but test and find out

 

[mjf55]

When you find the point of the problem, if you decide on fixing the existing wire, check it over for signs of corrosion. If the wire is corroded and you cannot get to a clean section, replace the wire. I would not solder as it cause a stiff area in the wire ( from the solder ) and is prone to cracking. I would use heat shrink adhesive lined crimp connectors. That will waterproof the connection.

 

[Thomasabbott91]

Ok I don't know what happened or if I did something wrong yesterday, but I'm getting off readings. Battery terminal readings were 12.62, amplifier, choke, and alternator were all the same with 11.81, ignition key purple was 11.90. Then it started raining so I'm going to finish tomorrow.

 

[alldodge]

I most cases you didn't have a good ground on your meter the first time

 

[Thomasabbott91]

So I tested the key switch and got 11.4 on both purple and red wires. And the purple wired on amp, choke, and amp was 10.8

 

[Thomasabbott91]

I used a different multimeter, last one broke. But still showing low

 

[alldodge]

Maybe retest the items listed in post 2

 

[Thomasabbott91]

What would cause the red and purple wires behind the key switch to be read below 12v?

 

[alldodge]

Bad connection and/or corrosion, check the 10 pin engine harness connector

 

[Thomasabbott91]

When I jump it, it wants to start. Other ways RPM stays at 250-300. Voltage is 10-11 volts under control panel, minor drop at ignition system (0.3v). I just going to pull the battery cables, clip them and put new heads on. A ground wire started smoldering and got real hot

 

[alldodge]

A ground wire started smoldering and got real hot

You have a bad ground connection for this to happen

 

[Thomasabbott91]

I cut the old ground wire at the battery and reattached it, then brushed ground wires under control panel...12v at ignition system, good spark, and boat started right up!! Thank you!!