1996 15 HP mercury with spark on only one plug

[99yam40]

Trying to help a friend with his motor that he reversed the battery leads on.
he replaced the rectifier, trigger, LS and HS stater coils, and switch box, but only has spark on one plug.
if you switch the trigger leads to the switch box the spark moves to the other plug.
after reading what I can find online it sounds like the trigger is not sending out a positive and negative pulse.

I do not understand how the trigger should be sending those + and - pulse.
I do not see any magnets on the center ring of the flywheel, but it does have a magnetic pull on a metal object I hold close to the ring.
I tried moving a small magnet along the ring, but did not feel a repelling force anywhere along the ring indicating a different magnetic field.

how does the trigger create the 2 different pulses?

 

[stresspoint]

i bought a cdi electrics cdi and i had to swap the wires in the plug once .pretty sure from memory that did as you describe.

be sure the part number matches on the new cdi ,they all look the same but a programmed differently .

 

[99yam40]

thanks but that does not help me understand how the one trigger coil is suppose to send out two different pulses (one Neg and one Pos) to the switch box telling when to fire the 2 spark plugs 180 degrees apart on the rotation of the flywheel.
as I said the only way we can get the other plug to spark is by swapping the 2 trigger wires going into the switch box(CDI).
still only one will spark , not both.
the best I can tell the trigger coil is not sending out a Pos and a Neg pulse.
I would think 2 separate magnets (arranged opposite N and South poles) passing by the coil 180 Degs apart on the flywheel would be needed to do this.

We cannot visually see or magnetically feel anything different on the center ring of the flywheel that rides close to the trigger coil.

 

[flyingscott]

CDI have the test procedures for your ignition.

 

[99yam40]

done all that testing, but there is nothing written about how to test the pos and neg pulses from the trigger or more importantly how they are made.
we did hook up a Simpson 260 to the trigger wires and rotated the flywheel with a drill motor,
all I see are pulses in one direction

this is why I asked about how they are produced.
are there hidden magnets in that ring or is there something else that I should be looking for.

 

[flyingscott]

Does that have the digital ignition without the manual advance?

 

[99yam40]

the manual advance moves the trigger coil around to change the timing

 

[flyingscott]

Well if the spark moves with the trigger wires what does that tell you?

 

[99yam40]

I am down to
either the flywheel that gives the trigger the magnetic pulses is bad
or the new trigger is bad.
this is why I asked how this trigger is supposed to do what it does.
and no one can explain how it functions/works, so it is a head scratcher.

 

[flyingscott]

Are you positive there are not 2 magnets?

 

[stresspoint]

thanks but that does not help me understand how the one trigger coil is suppose to send out two different pulses (one Neg and one Pos) to the switch box telling when to fire the 2 spark plugs 180 degrees apart on the rotation of the flywheel.
as I said the only way we can get the other plug to spark is by swapping the 2 trigger wires going into the switch box(CDI).
still only one will spark , not both.
the best I can tell the trigger coil is not sending out a Pos and a Neg pulse.
I would think 2 separate magnets (arranged opposite N and South poles) passing by the coil 180 Degs apart on the flywheel would be needed to do this.

We cannot visually see or magnetically feel anything different on the center ring of the flywheel that rides close to the trigger coil.

that would mean the CDI is either dead , or it is the wrong version unit for your motor.
as i said ! they look the same , but the magic stuff inside is different

 

[99yam40]

He said he checked the numbers on the original switch box, to order the ones he did
troubleshooting info says it should have Pos and Neg pulses out of the trigger that fire different SCRs in the CDI.
I am not seeing any neg pulses going to the CDI.
swapping the trigger leads into the CDI reverses the signal to Neg so the CDI fire the other plug but not both.
he ordered another trigger yesterday, so we will see if that does anything.
but it would be nice to understand how the trigger is able to generate those P & N pulses out of one coil with no visible magnets or even groves on the ring that the trigger rides next to.

as I said this is the reason I asked the question of how it works

 

[stresspoint]

maybe a faulty module.
pretty sure ??, it is done by the cdi unit / switch box ,not 100% sure about that .

 

[flyingscott]

Are you sure the magnet is not missing?

 

[99yam40]

why would it be sparking on one plug and not the other.
there are no magnets passing by the trigger that I can see or detect.
I would think it would need 2 magnets 180 deg apart positioned in opposite N S poles to give it the Positive and neg pulses.

my question has been and still is , how is the trigger coil suppose to put out a + and - pulse with no visible magnets passing by the coil?

 

[flyingscott]

Put up.a pic of this magic flywheel with no magnets.

 

[99yam40]

Put up.a pic of this magic flywheel with no magnets.

I do not have a pic of the flywheel, but if you read my posts above you will see it is the center ring of the flywheel that the trigger rides next to.
the outer ring of the flywheel has 2 magnets and the stator LS and HS charge coils and the lighting coils are what those magnets run by

 

[flyingscott]

Put up a pic of this ignition. I dont remember low and High speed coils on those motors.

 

[99yam40]

what are you calling the ignition you want a pic of

and what does it have to do with the operation of the trigger?

I did finally find this on the CDI electronics trouble shooting web site for mercury's, but not for the 1996 15 hp section.

The center hub on the flywheel also contains magnets mounted in a 360 degree configuration. Instead of generating electrical current though, these magnets simply tell the trigger/timerbase what position the crankshaft is at. As the magnets pass by the pickup sensors, the trigger/timerbase sends a signal to the power pack, telling it the precise moment to release its stored energy to the specific cylinder.

if the magnets are there, I cannot see them and I cannot detect them with another magnet

 

[flyingscott]

Good luck with your motor.