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Powerpack failure??

Keithm18

Regular Contributor
Hi All. this is a follow up thread to the one I posted a few weeks back.

Managed to get the boat back in the water today. Johnson 90hp 1981. Carbs rebuilt, fuel new, compression good (all indications are boat should run well) on last outing was down on power after Carb rebuild had cured it stalling when going to WOT after starting. thought it was a fuel delivery issue.

Turns out it's not a fuel delivery issue. I used a timing light with engine at idle in the water to see if all pugs were firing and they do, but one seems to fire intermittently. If you face the motor from the rear of the boat the one on the bottom left appears to have spark for a few minutes and then die out. I checked and confirmed all electrical connections are good. I then swapped out the power packs and the problem then moved to the right bank bottom cylinder. So I think that the power pack may be faulty.

After the swap it ran ok for two minutes at idle. I connected the timing light to that cylinder. It shows spark, but when the engine seems to miss the light seems to miss, but then It fires a little and then after a few more minutes it dies altogether.

my questions are as follows:
1) does this sound like typical behavior for a dying power pack?
2) are there any tests I can to with a multimeter to check if this is the problem, before I invest in new packs, because they are very pricy and I don't want to buy parts if it may be something else causing this.


thanks.
 
A common problem is that the pins/sockets within those rubber plug connectors will get pushed back slightly which results in a poor connection, which in turn results in erratic ignition/spark. Also, the wires where they are soldered to those pins/sockets have been know to break away but still have the inner wires touch the pins/sockets off and on so to speak.

This may not be your problem but it's something you would want to check out.
 
Thanks joe. I replaced the ones from the power packs to the coils with block connectors when I replaced the coils a few months ago, but didn't check the other connectors. Will do so and report back.
 
Thanks joe. I replaced the ones from the power packs to the coils with block connectors when I replaced the coils a few months ago, but didn't check the other connectors. Will do so and report back.

I neglected to mention that the wires that break away from the pins/sockets are still held firmly in the rubber plug connectors by the gripping action of the rubber... giving the illusion that the wire is still indeed attached properly.
 
Hi Joe and all.

I checked the plugs and removed the wires from the rubber boots and connected them directly outside of the boot where they looked funny. The attached is a linkt to what it's doing. The help is greatly appreciated. http://youtu.be/ukmIf1kPKeA
 
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Hi Guys. Quick update. I found a trouble shooting guide I downloaded some time back from CDI for the power packs.

I did the stator input diode test. This is where you place the voltmeter into diode mode then put the black lead to ground. With the pack disconnected place the red wire on the Brown wire, Then the Brown and yellow wire and then the White wire. The readings should be the same on all of them around 0.50 (500 odd on mine)

On doing this I found that on the side giving me the problems the brown and yellow wire and the white wire give me almost the same reading (480 odd), but the brown wire give me around 1 tenth (45)

On the other powerpack I get around 480 on all three individually.

Not sure that it's that simple, but the fact that the readings on the brown wire don't give me the same readings between the pack and the lower reading is on the side giving me hassles, I think this may be confirmation of a bad pack.

Guess I will be forking out again..............
 
Like dockside said connectors can be a problem. However, if you checked them and they are fine. You have move one pack in place of the other and the problem moved with that pack, then it is the pack (or you pushed a connector out of place). That test gets rid of the stator and the trigger and the coil. The only thing left is the pack. Especially if the cylinder which is connected to the color coded wire for the coil is exactly the same one as caused a problem on the other side.
 
Hi Guys. Quick update got the replacement power pack today and installed it. After a few tweaks to the connectors it's running better than ever before. Only had chance to run on the muffs in the drive. Will get chance to water test next weekend and will post results. I think this may have been the problem in going to WOT from Idle as opposed to the dirty carb theory.Anyway now have clean carbs and a new power pack so let's see what's to come.
 
Hi Guys. I finally managed to get back on the water this afternoon. after some fiddling I got it running pretty well. WOT almost back to normal. Hole shot a little flat, so I think I need to fiddle a bit more. Got it on the trailer and brought it home and then while flushing one of the cylinders has started to miss again. I give it a bit of a rev and it stops and then after a few minutes the miss is back. I narrowed it down to the bottom left cylinder. I replaced the plug and it cleared up but returned as soon as the engine warmed back up. There's no black dripping under the stator, but I am beggining to think this may be a problem on the stator... I tried plugging a timing light into this cylinder and when this problem occurs it's still got spark but it's definitely this cylinder. The plug is same color as the others so I'm positive there's fuel getting to the cylinder under WOT, but perhaps dirt in the idle jet again?? Any ideas please???
 
i see where you have used a timing light to diagnose the firing....that is good but have you checked to make sure you have the right amount of spark?..this engine should have a 7/16 good blue spark...this could be borderline on all cylinders and pick one to fail....swapping coils and power packs can be confusing sometimes if this is the case...
 
Hi Papyson. Thanks for the reply. I have previously tested the spark, which is what led me to replace the coils about three months ago and after that it was fine. I haven't retested as part of this trouble shoot, but I will do so and revert with the details.
The coils are new, the plug leads are new, the battery is new, the power packs are used but well within tolerance levels given my manual, the plugs are new, the rectifier works 100 %, all connections and grounds should now be good and there is no short on the stop circuit as I removed the stop wires at the pack yesterday with the same result. I suppose if the spark is weak it can only be the stator??
 
just watched that video....run the motor at night in complete darkness and see if you see any arcing to ground etc..
 
Hi Papyson and all.
I reconnected my spark tester this morning and found the same cylinder that was dropping out wouldn't jump the gap. checked connections and switched wires around but it still wouldn't jump. So I switched the coil with another from the other side of the motor and the problem moved!!
I then switched the coil with one of the old ones that were on the motor and BAM!! it jumps the gap. Started here up and she runs smooth as silk now. Not even a little blip of a miss. I will post a youtube vid a little later today.

The offending coil is a sierra part that's not even 10 hours old..... could the faulty diode on the power pack I replaced have killed it? Doesn't really matter but it kills me that a $25 part (That's what is cost me down here) didn't even last 10 hours.

I will run the motor tonight just for kicks to see if there is any arcing.. If I don't post back in a few days you will know that my neighbours didn't take too kindly to my testing.....

Just for fun I also attached a small picture of my home made spark tester.

IMG-20130224-00282.jpg
 
Hi All. This is one long thread but in the interest of not having to repeat information. The miss on my motor is back after one outing. Spark jumps blue over a gap of 7/16" on all cylinders, plugs all seem good. When idling though there is a definite miss, the motor is running erratically and now dies when cold if I don't raise the idle.
When warm it will idle, but misses badly and will sometimes shut off as if I switched the ignition off starts right up afterwards though. Have tried disconnecting black and yellow wires from power packs and it runs the same with the miss, have removed rectifier wires and the miss remains. Have tried removing one plug wire at a time and this obviously makes a difference, but there is no difference between cylinders as I remove/replace each of them in turn.
i ran the motor tonight in the dark and there is no shorting or visible arcing.

when on the water the motor will go to WOT but is definitely down on power and a little "rougher" than before.

Cdi's and coils test within range on the diode and resistance tests as does the stator and timer base. I don't have a DVA adapter to test the DVA readings.

the compression is good at 110 and 120 across the left and right banks and carbs are spotless. Fuel pump also 100%

This has to be an ignition problem. I have been avoiding removing the flywheel, but I'm beginning to think this has something to do with the timer base or magnets in the flywheel.

Does anyone have any ideas for me please?
 
Hi Guyjg. Plugs are new. Tested spark using spark tester. Spark blue across 7/16" and then tested spark on plugs all blue and gapped at 0.030. Ran motor last night, no spark leaking.

started motor today and let it warm up, miss was bad when when cold, but got a lot better when warm, water testing next weekend. I can deal with a small miss running on muffs. Water testing will show if power is back at wot.

Will let you all know
 
Pump some fuel out of the boat tank into a jar. It should be clear and not cloudy.l Lt it settle overnight...look for water on the bottom of the jar.
 
Hi All. Quick update. Flushed fuel system again completely and put some carb cleaner for outboards (sea foam equivalent) into carbs and tank. Put it in the water and ran it flat out this past Saturday and Sunday. WOT like never before, kept waiting for a stutter or a blip and it never came!!!

Brought it home and flushed it and it's never idled that smoothly before. I must have had some kind of microscopic fuel blockage in carbs or a build up of carbon in the motor, smoked like crazy for the first 15 minutes.

Sadly that was the last outing of my season.....so it's time to winterize and pack away properly for the winter.

Hope like crazy that the I won't go through the same challenges in Spring....

Thanks for all the help.
 
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