87 115hp inline 6 merc no spark

[ColdFire]

Hi guys,

Ok last year I had a problem with an intermittent spark and I fixed it with correcting some corroded wiring. Now a couple of weeks ago I lost spark on all but cylinder 1. I checked my voltages with a dva and found my trigger voltages low on all but cylinder 1. if I moved the tigger wire to other cylinders the spark followed so I replaced the trigger, I was also getting good voltages from the stator. Now when I go to try I have no spark what so ever. When I check my voltages I am not getting anything or very low voltages on both my stator and the new trigger. Is it possible the flywheel is bad? I have tried the ohm test and is says the stator and trigger are fine, but since I am not getting a voltage I am wondering about the flywheel. I've check the intallation of the fly wheel but it looks fine I don't see any cracks and the magnets appear to be fine. I am at a lost, I have a feeling this problem has been here for awhile but only showing up interrmitently.

 

[achris]

Re: 87 115hp inline 6 merc no spark

Hi,

This is a curly one. Which is why you're here... If it was easy they'd have monkeys doing it, right?

However, I digress.

These are my favourite engines... I shed a tear the day they discontinued them...

The ignition system should be quite simple; they have two, almost completely seperate, systems. One system fires cylinders 1,3,5, the other does 2,4,6. The only common points are, the kill switch, the flywheel magnets and the ground. I wish you had posted the DVA readings for the stators and triggers.

First test I'd do is to disconnect the kill wire (black/yellow) from each switch box and test again.

With such a strange set of symptoms, I'd then start looking at the ground wiring. You should have a heavy black on each switch box to the electrics plate, and another heavy wire from the plate to the engine block. Check all connections are clean and tight. Also check the battery ground. The kill wire uses that for the completion of the circuit.

After that I would be looking at the switch boxes, if one of them has been damaged, by a bad ground for example, then it can kill the other.

After that, I'm as lost as you... Post those DVA reading. Triggers should be about 2 volts, blue wire on the stator should be about 250-350 volts and red stator wire should be about 50-150 volts. All the cranking speed.

I once had an engine (115) that would idle nicely and run up to about 1200 rpms and then run on 3 cylinders. It turned out to be the high speed windings on the stator (red wires).

Have fun and let us know the results....

Cheers,

Chris.............

 

[ColdFire]

Re: 87 115hp inline 6 merc no spark

well the reading before the new trigger were:
Stator:
blue 300V
blue\w 240V
Red 38V
Red\w 40V
Trigger:
Brown 2.6
white 2.4
violet 2.0
yellow trigger:
brown 0.6
white 0.9
violet 0.6

Now I am getting nothing.... I am putting the old trigger back on to see if I get anything different. And yes this one has me completely stumped

OK after changing my dvm battery I started getting better readings. With the new stator the readings are identical... so I I should probably start looking for two switch boxes?

 

[Plainsman]

Re: 87 115hp inline 6 merc no spark

Can't you move on switchbox to the other side and see if the spark follows?

 

[ColdFire]

Re: 87 115hp inline 6 merc no spark

unfortunatly I don't get spark anywhere so I can't try that... I could try swapping the boxes and see if the low voltage from the trigger follows... I'll give that one a try. I have a feeling that a switchbox went out and took one side of the trigger out.

 

[Plainsman]

Re: 87 115hp inline 6 merc no spark

Your first post states that you lost spark on all but 1 cylinder. Sorry if it confused me.

 

[Laddies]

Re: 87 115hp inline 6 merc no spark

Have you disconnected th 2 yellow wires at the rectfier and the black yellow from the switch? does your engine have a idle stabalizer module if so disconnet it too

 

[ColdFire]

Re: 87 115hp inline 6 merc no spark

ok here is where I am right now.

The tw oyellow wires are removed from the rectifier the black yellow wires are removed from the switch boxes and the white black between the switch boxes is removed, and the idle stabalizer module is disconnected also.

I have swapped the switch boxes and the low trigger voltage follows the switchbox, so I have at least one bad switch box. and the stator voltages stay the same so I am pretty sure my stator is ok. So if anyone has any other ideas I am going to replace both switchboxes, or is it (I know not recommed) ok to replace just the one.

AChris, the better half reminded me after your post that I have been known to like a monkey every once in a while so I might just get this beast back up and going yet

 

[JUSTINTIME]

Re: 87 115hp inline 6 merc no spark

are u testing switch box output
that will tell u
and u are using a dva also right

 

[Laddies]

Re: 87 115hp inline 6 merc no spark

If the bias tests good in the box you are planing to reuse it will be OK to switch just 1 box

 

[ColdFire]

Re: 87 115hp inline 6 merc no spark

one more quick one... I have verified I have good outputs from one of my switch boxes ( I didn't notice the my little girl readjusting my spark tester ) When I swap the stator leads the problem stays with one box. so if i replace just the one, does it have to be a mercury part or will a cdi work with an older merc switch box?

 

[JUSTINTIME]

Re: 87 115hp inline 6 merc no spark

cdi is 10x better than oem