red/black wire to bypass mpem for spark test

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glenwhitt

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I see some threads that talk about disconnecting the red/black wire from the mpem to the coil but i do not see this wire. is it on the 96 challenger? I see a white one.

My boat was doing great the other day when it just shut off. from 6,700 rpm to zero. cranks over fine. tested all fuses in box and under the hood. I have zero spark on the plugs.

If i can not get it to spark with the bypass above, it is said to be coil or stator the cause. Any way to test each of these before replacing them also?

Will take of electrical box if needed.

Thanks
 
just for spark test

I wanted to bypass the rev limiter to do a spark test. i heard there was a wire I could unplug on the coil that would do this. If it sparked then I need an mpem. if i still have no spark then it is somthing from the stator up to the coil that could be the problem. I have a white wire and black wire on my coil. I removed the black wire and no spark still (i think this means it was not the mpem fault and i am very happy about that).


Anyway to test the stator and trigger to the coil. Can you use a test light while turning over the see if i get a pulse? would i use the white wire for this?
 
hey glenn...try the white wire now..if no spark, (relief..:)), then yeah, coil or stator, but think it lies, more in stator assy. I dont have/find "test" procedure, but do know, its in the manual...or simpler test, is to get a plug with the yellow and black wires and plug at magneto plug, but dont know the procedure...still look'n for it.
 
ok

Thanks Timmyboy

Wll try white wire off and black wire on tonight to see if i have any spark (still hoping for no :) )

The shop manual shows me the test for the coil and the stator. I will try those over the next few days also. And let you know what i come up with.

If the mpem is bad it will be a tough decision to fix or just sell/part out.
 
good news !!!!

I have no spark no matter what wire I disconnect from the coil. So i guess the mpem is good, or at least not the only problem :)

Tested the primary winding resistance per the shop manual and i am getting
0.80 when the book says it should be 0.34 to 0.62. What do you guys think? Would this much dif make it not spark? It also says even if the coil passes test it may still be bad under load. I was not able to check secondary winding as i do not have the seadoo tester for this. No time tonight but I will try and check trigger coil tomorrow. Maybe a weak coil is the reason i could never get my rpms back to what they use to be. Weak spark and all?????
 
That should still work… but if the coil is the original, it is a sign that the interior wire is breaking down, But since you are dealing with very low resistance values… I would check/verify your meter with a known source (a resistor) and make sure that you wipe down the outside of the coil to make sure there is no other paths to ground. Lastly… make sure you aren’t holding any of the metal contacts of the meter probs.

High primary resistance can lead to a weak spark.
 
Thanks Doc

Thanks for the info doc. I tested it while in the electrical box. It is still there. After I am done testing the stator and coil trigger I can then get down to figuring out what parts I will need to make her run again. I will probably get a new coil though. I hate for anything to be "weak". Any suggestions for a coil? OEM or maybe something aftermarket with a hotter spark?

I will go to radio shack or something like that to get a resister and test through it. My multi meterr is only a few weeks old but I got it at checker so no telling :)
 
If you go to radio shack to buy a resistor… make sure you buy something that has a very small resistance value. (around 1 ohm) Then… make sure the one you get is a “precision” resistor. They are normally colored blue. A typical resistor has a 5% to 10% tolerance value.

The real problem is… the meter you have may be perfectly good… but it’s calibration may be off a little. I have a few around my shop like that… but I know what the drift amount is.

Good luck
 
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Calibrate digital?

Mine is digital so is there still a calibration to it? I am unable to find the doc on it now. Will have to try and find it on the web. Thanks !!!
 
The latest test is in, Please help

I did some more testing tonight. I have good specs on the pickup when i tested it with digital ohm meeter. I cranked the engine around by hand while the meter was hooked up and it did not budge. Solid 247, well in spec at 242 +/- 10%. So i went back to the coil and tested for spark again after I got everything hooked up. Nothing. I then put my meter on voltage test and put + lead on the white wire to the coil and grounded the - lead to the engine. While cranking i get voltage. it goes up and down so fast I am unable to put a number to it. I did see 12+ volts though a few times.

I did the coil test again and it showed 1.1 this time instead of the .80 it did last time. taped the coil with my fingers and it started moving around from 1.1 to .60.

I think my option at this point is to get a coil for it. Hello Parkeryamaha, can you take some more of my money please :)

Please let me know what you guys think because i want to get the coil ordered tomorrow before noon so it can be here for the weekend. Thanks !
 
ordered a coil

Well no one spoke up on the last post :) so i ordered the coil tonight. Will leave the store tomorrow and be here Friday. I pulled the old coil out and tested post to post and end of plug wire to end of plug wire again. I am hoping this is the problem as i tap the coil with a screw driver the readings change drasticly when doing the plug wire to plug wire test and the post test. Not sure if this is normal but what the hell. Its only money :(

I am also reading that the cdi has control of the spark but i am not able to see how with only two wires to the coil, one ground and the other a white wire that is getting current pulses when turning over. Does the white wire come from the cdi? Anyone have any info on this. Those things are #$$%^ expensive. Timmyboy, will that msd box replace the cdi also? That option is looking better and better. I may have to call Brett at MSD again and ask some more questions.

Thanks !
 
Sorry I didn’t get back to you on this…

Anyway… since the value was changing… I would get a new coil. (you already did) If you get a value change from physical vibration… then the wires inside are cooked. The only time you should see a drift in the numbers is from heat.

I just looked at the wiring for your boat, and the white wire goes from the CDI (capacitor discharge ignition) to the coil, and yes, the CDI controls the coil. The reason it can control it with one wire is because the coil works by the induction of a magnetic field, and it only takes power going to ground to charge/discharge the coil. The CDI builds a charge via the 12v battery, and it discharges into the coil once it sees the timing signal from the trigger coil. The quick discharge of the CDI induces a magnetic field in the primary windings of the coil. Then when the CDI cut the power, the field in the coil collapses, and induces a high voltage spike in the secondary windings, and the spark plug is the ground source of the secondary windings. BTW… this all happens in a fraction of a second. Depending on how sophisticated the CDI is… it can set the timing, or the spark intensity.
 
good info

Dr Honda said:
Sorry I didn’t get back to you on this…

Anyway… since the value was changing… I would get a new coil. (you already did) If you get a value change from physical vibration… then the wires inside are cooked. The only time you should see a drift in the numbers is from heat.

I just looked at the wiring for your boat, and the white wire goes from the CDI (capacitor discharge ignition) to the coil, and yes, the CDI controls the coil. The reason it can control it with one wire is because the coil works by the induction of a magnetic field, and it only takes power going to ground to charge/discharge the coil. The CDI builds a charge via the 12v battery, and it discharges into the coil once it sees the timing signal from the trigger coil. The quick discharge of the CDI induces a magnetic field in the primary windings of the coil. Then when the CDI cut the power, the field in the coil collapses, and induces a high voltage spike in the secondary windings, and the spark plug is the ground source of the secondary windings. BTW… this all happens in a fraction of a second. Depending on how sophisticated the CDI is… it can set the timing, or the spark intensity.
Click to expand...



Great stuff here doc. Since i am getting a pulse from the cdi to the coil then maybe this coil swap will do it. If not I will inspect the stator and trigger, along with getting a cdi box i found for $270.00. This is below dealer cost and new oem from seadoo. I am buying it anyway so I have a spare.
 
Dr Honda said:
Sorry I didn’t get back to you on this…

Anyway… since the value was changing… I would get a new coil. (you already did) If you get a value change from physical vibration… then the wires inside are cooked. The only time you should see a drift in the numbers is from heat.

I just looked at the wiring for your boat, and the white wire goes from the CDI (capacitor discharge ignition) to the coil, and yes, the CDI controls the coil. The reason it can control it with one wire is because the coil works by the induction of a magnetic field, and it only takes power going to ground to charge/discharge the coil. The CDI builds a charge via the 12v battery, and it discharges into the coil once it sees the timing signal from the trigger coil. The quick discharge of the CDI induces a magnetic field in the primary windings of the coil. Then when the CDI cut the power, the field in the coil collapses, and induces a high voltage spike in the secondary windings, and the spark plug is the ground source of the secondary windings. BTW… this all happens in a fraction of a second. Depending on how sophisticated the CDI is… it can set the timing, or the spark intensity.
Click to expand...
Wow wow wow You seem to have very good knowledge on the this subject sure hope that you stay a round so that we can all learn from you. Robin :cheers:
 
One test down, more to go

Well the coil arrived today so it tested it on bench, .80 ohms on tab to tab and 14.2 wire to wire. All was steady when tapping lightly and tipping side to side. Installed and no spark. Went back to basics and did some more reeding. I am hearing the CDI gets its signal from the coil trigger in the mag and the CDI is what sends the voltage to the coil. Is this true?. I tested with digital volt meter and when lanyard is on and I get the two beeps and I am getting 11.3 volts to the white wire on the coil. When I turn the engine over it goes down to .3, and stays there steady while cranking. When I stop cranking it jumps back up again. Is this telling me the trigger is working in the mag but the CDI is not putting out? I really dont want to take the cover off if i do not have to. Does the mpem have any control on this white wire also? So my questions are;

1. Does the CDI gets its signal from the coil trigger in the mag and does the CDI send the voltage to the coil via the white wire?

2. If I get 11.3 volts at the white wire on the coil with power on and non cranking, and then when cranking I get .3, what is this telling me?

3. Does the mpem control the voltage to the white coil wire?

4. Am I correct in saying I should get a high/low reading when testing volts on the white wire on the coil when cranking.

Thanks for taking the time answer some questions :)
 
This may get long… so bear with me….

Let’s start with the questions…

1) Yes, the CDI gets its trigger signal from the coil in the mag. That wire should be yellow/white/green. And yes… the CDI gives the coil it’s voltage.

2) I would think you should see more voltage at the coil, but 11.3 should be ok. The reason the voltage goes low while you crank is because the CDI is getting ready to send the coil a charge signal. A typical multy-meter can’t see the voltage spike to the coil. To see the resolution needed for the ignition voltage (to the coil) you would need an oscilloscope.

3) No, the MPEM doesn’t control the voltage to the coil, but it does control the CDI. (more on this)

4) Yes, you should get a high low… but your meter may not be able to see it. (need an O-scope)

OK… as I was looking over the wiring diagram for your boat, there are 3 wires going from the CDI to the MPEM. One is a ground. (black) a tach signal (gray/white/green) and one marked as “Code.” (white/blue/green) This code wire is how the MPEM controls the CDI. On the older system, this was simply a ground to kill the ignition (that’s why you could disconnect it and get a spark) but on the newer system with the security key… I’m not sure if that’s all that is happening with that connection. You can try to disconnect that wire from the MPEM box to see if you get a spark. (I’m not saying it will work, but it may)

On the CDI, there is a wire (red/purple/green) that is the power wire for the CDI. Just for the sake of checking… see if it has 12v when you get your 2 beeps.

Just for an FYI… I’m relatively new to the Sea-Doo world, but I own a motorcycle shop, and the 2 stoke ignitions are basically all the same… but with the addition of the security feature is where my knowledge will drop off.

Let me dig around the service manual to see if I can find anything else you can test for.
 
OK… I’ve dug into the service manual for your boat, and I’m getting conflicting wire colors. So my first question is… do you have the service manual for your boat?

Just a few things I’ve found….

YES… you should be able to check for a bad “Rev Limiter” by lifting a black/red/green wire. A bad rev limiter will keep the ignition form working. This is also the wire that kills the engine(787) when the start stop button is pushed.

Confirmed… the CDI controls all the ignition and timing, so, it should run as a standalone unit if it’s good. (ie, could run without the MPEM)

Your trigger coil should check as 242 ohms between the yellow/white and the black/yellow wires.

The only thing I can’t find any info on is what the “Data” is between the CDI and the MPEM to check it. It could be basic logic, or it could be a full data stream. The only thing I found was that it is low voltage, so it’s data of some sort. This wire could be what is keeping you from running, and unfortunately, if that’s the case… it’s time for a new MPEM. My boat has a 720 engine, so I can’t hook up a logic probe to a running boat to find out what it’s doing.

If I were you… I would put out a plea to everyone local to you with a 787 seadoo, and swap some parts until you find what’s not working.
 
Thanks for the data !

I have printed out the wiring diagram from the 96 challenger service bulletins and follow along with you.
I agree that disconnecting the black wire from the coil DOES NOT bypass the mpem as I thought before. This wire goes straight to ground so unplugging this will guaranty no spark.

I also see the yellow/white/green wire in the diagram labeled as “RPM Limiter wire / ignition system generator coil” coming from the mag to the CDI then the white/green from the CDI to the coil.

I see the red/purple/green coming from the 5 amp fuse from the mpem to the CDI. Will check that for volts after I get the two beeps.

I have started to remove the mag cover since I will never know what the condition it is in until I sneak a peek. Trouble getting the last two bolts out on the bottom. Not able to get wrench or socket on them, even with front motor mount removed and engine lifted up in front. Will have to pull pipe and then the pump to get engine to slide back enough to get to these (I was dreading this).

Looks like I have some work to do. Thanks !
 
black/red/green wire

I do not show this in the diagram nor can i find this in the box. Where is it suppose to be?

I have good specs on the pickup when i tested it with digital ohm meeter. I cranked the engine around by hand while the meter was hooked up and it did not budge. Solid 247, well in spec at 242 +/- 10%.

I have a shop manual but i think the service bulliten i have is more up to date with the wire diagram.

What do you think about this doc if I find the mpem is bad?

http://www.msdpowersports.com/pwc_seadoo.html

The (PN 4255) with the (PN 42551) would completely replace my mpem. I can get the whole setup direct from them for like $500.00 but more like $350 to $400 he said if I use a dealer of theres.
 
The MSD thing is cool. It looks like a standalone computer for a Sea-Doo. If it’s cheaper than the MPEM… then get it. It will probably make better power. The only down side is that you loose the security key.

On your trigger coil, you won’t see a change in the resistance when you turn the engine. But, if you put your meter on DC volts, and turn it by hand, you should see a small voltage generated when the timing marks line up.

The wire in question is one that I have conflict with. The shop manual says the colors in the trouble shooting section… but I don’t see it on the diagram either, and since I don’t have a 787 boat… I can’t check. (sorry)
 
Dr Honda said:
The MSD thing is cool. It looks like a standalone computer for a Sea-Doo. If it’s cheaper than the MPEM… then get it. It will probably make better power. The only down side is that you loose the security key.
Click to expand...

Cheaper by like $600.00 :)

Dr Honda said:
On your trigger coil, you won’t see a change in the resistance when you turn the engine. But, if you put your meter on DC volts, and turn it by hand, you should see a small voltage generated when the timing marks line up.
Click to expand...

Yes i get this also. Seeing as I am passing all the test form the stator I will not finish pulling the mag cover off until after I tested the new CDI on Monday. Maybe that will do the trick :) In order to get the last two bolts out I am going to have top slide the motor back (take off pipe, jet pump and drive shaft, unbolt motor. What a pain)

Dr Honda said:
The wire in question is one that I have conflict with. The shop manual says the colors in the trouble shooting section… but I don’t see it on the diagram either, and since I don’t have a 787 boat… I can’t check. (sorry)
Click to expand...

Not only is it not in the diagram but it is not in the electrical box in my boat either. I have carefully looked at every wire in there.

Thanks again doc. BTW: I have Humana so just bill them :)
 
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