'85 115hp Evinrude - Weak Spark on Port Cylinders

[Auxlarry]

I think I created a monster!!
My engine hadn't been run in a year or so and when I got it all prepped (including new water pump) it only fired up on the right hand bank of cylinders. I did the normal trouble shooting, power pack and coil swap and had the same results. Well, the wiring under the cowl looked bad, cracked insulation, etc, timer wires were all nasty as well as the stator. I decided to bite the bullet and replaced the timer base, stator and both power packs with all new CDI parts. Looks great but guess what? Still have the same issue, no fire on the left bank of cylinders. What might I be overlooking? I cleaned all the grounds, new batteries (it turns over nice and fast) and fires right up on the right bank ( cyl. 1&3). I need some help on this one folks!!
I am getting fuel! Part of the prep was to rebuild the carbs but I have no spark on left, great spark on the right! (with spark detector).

Thanks,

Larry

 

[Auxlarry]

Update:
I did some trouble shooting and did a compression check, all cylinders are between 115 and 120 psi! Power head only has 27 hrs on a rebuild. Pulled the blk/.yellow wire from the plug at the power pack thinking I had an issue with that but it made no difference. I'm a bit stumped. Didn't replace the regulator because it's only a couple years old but I don't see where that would be an issue with one side not firing. Any help is appreciated!!

 

[boobie]

The regulator has nothing to do with the spark. Go to cdielectronics.com for trouble shooting procedures.

 

[Auxlarry]

I didn't think so by going through the schematic. I have CDI's troubleshooting pages for all the components and just noticed in the shade I have week spark on both cylinders, maybe 1/8"-1/4" where I have a good 7/16" on the bank that is firing.

 

[Auxlarry]

Went through the CDI troubleshooting guides for all the parts and everything checks out resistance wise, I don't have a DVA meter so I can't check that. All new parts and still the same problem I started with. What am I overlooking??

 

[Auxlarry]

Anybody have any ideas??

 

[boobie]

To check anything properly on these motors you need a DVA adapter or a Peak Reading Volt meter.

 

[Bosunsmate]

run it at night, see if its arcing out somewhere

 

[Auxlarry]

Ordered a DVA and should have in a few days. I'll let you know the results.

Started last night and saw nothing unusual, no sparking etc. Still weak spark on port side with good strong spark on starboard side!
Thanks for the reply's guys!!

Larry

 

[emdsapmgr]

An unusual problem! Unlikely one of the brand new power packs is bad, but you could try swapping them to see if the "no spark" condition moves to the other head. Also, the 4 coils on that engine are usually pretty bullet-proof, but you could swap two of them between heads to see what happens. Agree with boobie-check the stator cranking output with a dva meter. Probably should be around 150 volts, but check the service manual or the CDI website for the exact voltage-that's the minimum output voltage to condemn from. That might indicate something, possibly including a bad flywheel. Do the same for the timer base. You did not mention new spark plug wires. Not usually a problem but, you could check them out by running the engine with the cowling off at night. If the spark plug wires are going to ground-you'll see it at night in the dark.

 

[Auxlarry]

Emdsapmgr
I did all of that, swapped coils, pack and had the same issue. Starboard side had good strong spark and fired an ran fine on them but still had weak spark on port. I tried swapping the stator leads from side to side but need to make a better jumper. When I swapped the stator leads from one side to the other I did not get the starboard or port side to fire but my jumper was rather crude. I'll try again when I get my DVA.
Flywheel???? Why would that be an issue since it is firing fine on one side? I need to read up on the flywheel!!
Plugs and wires are new as are the stator, timer, coils and packs and have the same problem I started with.

Thanks for the information and the reply!!
Larry

 

[emdsapmgr]

That's why I asked if you tested for cranking voltage output. If you have low cranking voltage output, it may not fire all the cyls all the time. Usually, a weak stator will cause random misfires, and your is constant on the same cyl. Could also have something to do with weak magnets on the flywheel-a real rare condition..

 

[Auxlarry]

New batteries, new cables all the way to the motor, cranks great and fires on 1,3 almost instantly. I'm still a bit miffed about the flywheel magnets you mentioned? I would think that weak magnets would cause issues with both sides of the stator. I don't have intermittent fire on 2,4, just weak spark, it fires every time but even notice a weak signal on the timing light. Just have to wait for my DVA to arrive so I can chase this monkey down. I'm just a bit surprised that after changing the entire ignition system I have the same issue I started with!!

 

[emdsapmgr]

That's why you start looking for other, unusual electrical aspects of the problem, like a bad flywheel or perhaps a coil going to ground, even a wire chafed from flywheel rotation. Don't forget the flywheel has the outer magnets that create voltage, and the center flywheel ring has magnetic strips that determine firing timing. You originally decided to just replace the whole ignition system...you might want to replace one new component with an old one, as a test. (you did not say the old ones were determined to be faulty) Have you checked the cranking output voltages from the timer base and stator yet?

 

[Auxlarry]

Emdsapmgr,

I changed all the parts for a couple reasons, 1) All the wires from the stator and timer had crumbling insulation and the wires were very brittle, couldn't strip back far enough to get good wire or strong insulation. 2) Had weak spark and no fire on the Port side!! The exact same problem I am having with all new parts!!
The flywheel questions you raise are interesting. I was under the impression that if my starboard side was firing then the magnets in the flywheel should be fine? I have tried finding information on the workings of the flywhell but haven't had any luck!! My DVA is scheduled to be delivered today and I plan on working on the motor tomorrow, I'll get all the voltages then!!

Thanks!!

Larry