Force 120, no spark on #1...running out of places to look

[rich_kildow]

Hello all. I have a 1208x90B 120hp (4 blue coils and 2 blue CDI packs) Force on my 1990 Bayliner Cobra dual console. I had it out about 2 weeks ago for the first time this season and it was running great, then suddenly lost power and sounded like it was missing on a cylinder. Started pulling plugs and listening for a change in RPMs and sure enough, #1 (top) wasn't firing. I tried a new plug with no change. I have the service manual and the CDI troubleshooting guide and I've been going through the steps, so here is what I've checked, with no fix so far:

- New plug
- Swapped plug lead and trigger lead from Coil #2 to fire cylinder #1, got spark on #1
- Hooked trigger lead for 2 up to 1's coil, got spark on 1
- Tried a new coil from my parts on #1
- Pulled flywheel, looked for abraded wires or any signs of where
- Flywheel key was good
- Checked resistance from orange to green on trigger wires while disconnected, 52 ohms is within spec
- Checked stator wires for front pack, 728 ohms is within spec
- Disconnected stop wires for other pack
- Disconnected all wires from rectifier

I read this as coils are good since I have spark from both coils when fed from cylinder #2 input from the power pack The resistance tests would indicate to me that the coil and trigger are good, assuming they pass the DVA test tomorrow.

Is all this indicating a bad power pack?

 

[Jiggz]

Coils are good both on #1 and #2 cylinder. The next troubleshooting is to switch the CD modules (power packs). I understand, this takes a lot of work and is much easier if you have a spare CD module. After the switch and #1 cylinder continues to have NO spark, then the problem is with the trigger. But if the NO spark follows with the switch, i.e. #3 or #4, then the CD module is faulty. YOU DO NOT NEED TO RE-SWITCH THE CD MODULES BACK UNLESS YOU WANTED SO.

And yes there are two separate circuits in each CD module and one can actually go bad without affecting the other.

 

[rich_kildow]

That's what I was thinking...and afraid of. I know just enough about engines to stop before I get in trouble and to confirm my hunches with the experts.

I'll get to work on that and report back.

 

[Jiggz]

If any you can take pics of original wiring or write down the connections and colors. This should help if you have to go back to the original configuration.

However, if you have a DVA tester, do the DVA test first on the CD modules outputs and a simple comparison of readings should tell you which CDM is faulty.

 

[rich_kildow]

Swapping them wasn't bad, and the problem appears to have moved. I'm going to get it hooked up on the hose for a minute to make sure but I'm thinking I have a bad power pack.

This boat was stored for the first 25 years of it's life and never used, just maintained, so it is like new condition. The factory labels are on all the stator and trigger wires, and the wiring diagram on top of the block is still there.

 

[rich_kildow]

The problem moved with the box and is now on the bottom cylinders. With the swap, I went from #1 having no spark to #3 and #4 having no spark. I had suspected that I #2 may have been intermittent during the initial troubleshooting, or I may have finished off the circuit from all the testing...or just not hooked something up right. I'm going to call around to all the local places tomorrow and see if I can find one in a parts bin or something. I'd love to have it up for the 4th but that isn't going to happen if I have to have anything shipped.

 

[st72ay bull3t]

Just wondering i have a 87' force 125 did compression test cold motor one plug out at a time came out 120# , 120# , 120# , then got to number 4 plug it had condensation on it and it is only 90# 10% should be 12# difference i think. Having a hell of a time starting her. Should I come consider her serving a long life, put her to rest, and get a new outboard oh dang was trying to start new but responded instead... sorry guys

 

[jerryjerry05]

Just wondering i have a 87' force 125 did compression test cold motor one plug out at a time came out 120# , 120# , 120# , then got to number 4 plug it had condensation on it and it is only 90# 10% should be 12# difference i think. Having a hell of a time starting her. Should I come consider her serving a long life, put her to rest, and get a new outboard oh dang was trying to start new but responded instead... sorry guys

You have a post already.

 

[jerryjerry05]

The trigger leads can be broken under the shrink wrap.
Try pulling the leads and see if the wire comes loose.
​I change the connectors, just in case.

The pack has a blocking diode that can go bad and cause this problem.

​The stator even though it reads good can be bad.

 

[rich_kildow]

I checked all the wires at both ends for both the stator and trigger and found nothing, and everything checked good for resistance. My DVA meter just showed up so when I'm done replacing the impeller this morning, I'll check those.

I ran the test for the blocking diode by disconnecting the kill wire from the other pack, and that did not restore the cylinder.

As for dropping both bottom cylinders now, I'm wondering if I didn't hook up the wrong leads to the coils and have 3 & 4 reversed (which are now running off the suspected bad pack after I swapped them.)

 

[rich_kildow]

UPDATE: I did have the leads going to coils 3 and 4 reversed, so neither cylinder was firing. I swapped them, ran it on the hose, and sure enough cylinder #3 was dead. It is definitely the CD module. I found the whole ignition system on ebay for $110 shipped. Stator, trigger, terminal boards, mounting panel, 4 coils, 2 CD modules, rectifier/regulator, solenoid, etc!

I also replaced the impeller while I was at it, which definitely needed to be done.

 

[Jiggz]

Great. That'll give you some spare parts for your parts bin. Anyways, as soon as you replace the bad CDM post your results.

 

[rich_kildow]

The motor is fixed and running well. It was indeed the CDM and I had all 4 cylinders running as soon as I swapped that out. I'm hoping to get it out on the lake today to set the idles and make sure all is well.

 

[Jiggz]

Great. For initial setting I always set the idle in neutral on muffs around 1000~ 1100 rpm. And this converts to around 700~800 rpm idle in gear on the water.

 

[rich_kildow]

I messed with the idle out on the water today and it is idling better than ever before. It was always a bit finicky getting started, and I only just now discovered the throttle advance :facepalm:. I turned them in 1/8 turn from where they have always had been and it stopped dying when you first put it in gear!

 

[jerryjerry05]

"set the idles" ??
​The idle is set at the towershaft.
The screws on the carbs are for air/fuel mix at idle.
​Sometimes/ most times adjusting the air screw will increase and smooth out the idle.

To set the air screw: gently in till it just bottoms out.
Then out 1 1/2 turn out.
There is an equalizer hose between the carbs.
​You need to pinch this off.
Then motor running in the water.
Preferably in gear.
​Turn the top air screw in 1/8th a turn until the motor kicks, buck, stalls.
Then out 1/2 turn.
​You need to wait 10 seconds between the turns to burn the fuel at the old setting.
Repeat on the bottom carb.
Then do it again on both carbs.

But before you do any adjustments. Clean the carbs and make sure the floats are set right.

 

[rich_kildow]

Correct, I should have said "set the idle mixtures screws." The idle point has always been fine and I confirmed it per the service manual. I brought a hose clamp with the isolate the carbs and they were both in need of the exact same adjustment. I believe they both sit 7/8 of a turn out.

The service manual I have specifies 1 turn out from light seat for almost every model covered for the idle mixture screws.

 

[Jiggz]

And I strongly recommend you leave the idle mixture screws at 1 turn out and should never be adjusted below this setting. Otherwise, you can have catastrophic problem with that engine due to lack of lubrication.

If you are having problems starting it from cold state, make sure you do the proper cold starting procedures, primer bulb, fast idle and choke.