keithjohnson49
New Member
My 98 GTX Limited started blowing the 15A Batt fuse in the MPEM today. Any suggestions for the most likely place to check to see what is shorting? Appreciate any help.
Keith
Keith
98 GTX Limited blowing 15A Batt fuse in MPEM
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Sportster-2001-951C-Stock
Well-Known Member
Does the fuse blow immediately with lanyard off post or only once the lanyard is placed on the post? I'm guessing at this point the charging circuit is at fault, ie: regulator rectifier or stator might be shorted or perhaps the electric pump nozzle trim motor?
I don't immediately recall which engine that model has, or if the rectifier/regulator is external or internal of the MPEM, but you'll need to begin troubleshooting by disconnecting suspect circuits.
I don't immediately recall which engine that model has, or if the rectifier/regulator is external or internal of the MPEM, but you'll need to begin troubleshooting by disconnecting suspect circuits.
keithjohnson49
New Member
It's blowing after the lanyard is on. It will start and run for a few seconds then the fuse blows. On the 951 the rectifer is internal to the MPEM.
Sportster-2001-951C-Stock
Well-Known Member
Ah yes, I guess all the carbed 951's had the RR internal of the MPEM, as mine does. On the surface it seems the RR is involved with the short circuit.
If your RR is found to be the issue you can wire around it and install an external RR. Attached are an example unofficial 3-phase RR internal schematic FYI, and by examination of figure 5 you can see how the diodes and SCR switches can easily be tested for shorts. Pretty sure this is the same design seadoo used for the regulator, but I haven't confirmed that.
Also, remove connector #2 and test the stator (3 yellow wires) to make sure the resistance is around 1 ohm between any/all of the three and there is infinite resistance to engine ground (no continuity to ground) of any of the three yellow wires.
If you do that, install a 15A fuse in the RR output red wire close to the RR too, sorry I forgot to draw that important detail into the changed schematic.
I can't imagine any other reason for that particular fuse to blow.
If your RR is found to be the issue you can wire around it and install an external RR. Attached are an example unofficial 3-phase RR internal schematic FYI, and by examination of figure 5 you can see how the diodes and SCR switches can easily be tested for shorts. Pretty sure this is the same design seadoo used for the regulator, but I haven't confirmed that.
Also, remove connector #2 and test the stator (3 yellow wires) to make sure the resistance is around 1 ohm between any/all of the three and there is infinite resistance to engine ground (no continuity to ground) of any of the three yellow wires.
If you do that, install a 15A fuse in the RR output red wire close to the RR too, sorry I forgot to draw that important detail into the changed schematic.
I can't imagine any other reason for that particular fuse to blow.
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keithjohnson49
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Thanks for the reply. I did splice a new thru connector on the rear elect box last year that was shorted due to corrosion. Looks like that's part of the charging circuit. One of the vacuum bailer tubes came out last year and flooded the skil before I caught it. I've been chasing electrical ghosts in this thing since. I'll check to make sure the repaired splices are intact. If no problems there, I may just breakdown and replace the MPEM with a used unit.
keithjohnson49
New Member
OK, after reading some more on the charging circuit, I think I know where I screwed up to cause the fuse to keep blowing. Just need some validation from some more knowledgeable non-idiots if someone can weigh in before I spring for an MPEM.
Right before I took the ski out last weekend, I put a low-amp battery charger on it while the battery was installed and hooked up. I knew about the danger of jump starting, but didn't realize that even a low-amp charger would still fry the innards of the MPEM.
All the connections, etc. are clean and I can't find any shorts anywhere. It fires up and runs for a few seconds and then blows the fuse. What do you guys think.....just get a replacement MPEM?
Right before I took the ski out last weekend, I put a low-amp battery charger on it while the battery was installed and hooked up. I knew about the danger of jump starting, but didn't realize that even a low-amp charger would still fry the innards of the MPEM.
All the connections, etc. are clean and I can't find any shorts anywhere. It fires up and runs for a few seconds and then blows the fuse. What do you guys think.....just get a replacement MPEM?
[MENTION=41828]Minnetonka4me[/MENTION] can give info on a basic test for the MPEM
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keithjohnson49
New Member
Narrowed it down with everyone's help. Disconnected the connector on the front of the mag cover and turned the engine over, Everything works and the fuse doesn't blow. Reconnected and it blows immediately. Looks like something's shorting out inside the mag cover.
Although.....I would almost rather it have been the MPEM. Lots more money, but waaaay easier to replace on the 951 than pulling the mag cover!
Although.....I would almost rather it have been the MPEM. Lots more money, but waaaay easier to replace on the 951 than pulling the mag cover!
Sportster-2001-951C-Stock
Well-Known Member
I think most likely there's a shorted diode in your MPEM's internal regulator, you can install an external RR as mentioned above but test the stator for shorts first.
Yep,, what he said.. It can still be in the MPEM as the Stator and MPEM work directly together. But the stator is testable, so you can isolate it out for sure..
keithjohnson49
New Member
Hey guys, one more request for some advice.
I checked the 3 yellow wires from the mag connector and there is continuity between all three but open when grounded (I checked them at the MPEM connector). Then I put a voltmeter on the yel/blk and blk/yel and cranked the engine, got 12 volts. I unplugged the MPEM connector and jumped the solenoid and the engine cranks.
Couple of weeks ago, I had the mag cover and flywheel off to change the bendix, and I cleaned it all pretty good so unless something came of the new bendix/flywheel to short it out....?
I'm leaning now towards a bad MPEM, but wanted some advice on whether I had done the test right. Guess I want to be sure before I rip everything out to pull the mag cover. Any thoughts?
Thanks for any help.
I checked the 3 yellow wires from the mag connector and there is continuity between all three but open when grounded (I checked them at the MPEM connector). Then I put a voltmeter on the yel/blk and blk/yel and cranked the engine, got 12 volts. I unplugged the MPEM connector and jumped the solenoid and the engine cranks.
Couple of weeks ago, I had the mag cover and flywheel off to change the bendix, and I cleaned it all pretty good so unless something came of the new bendix/flywheel to short it out....?
I'm leaning now towards a bad MPEM, but wanted some advice on whether I had done the test right. Guess I want to be sure before I rip everything out to pull the mag cover. Any thoughts?
Thanks for any help.
Sportster-2001-951C-Stock
Well-Known Member
Based on none of the three yellow stator wires has continuity to ground, the fuse blowing is caused by a shorted rectifier diode in the RR circuit.
I would probably bypass the internal RR(remove BATT fuse) and install an external RR such as the one used for the 951DI or 787RFI Also, there are kits available for converting to external but it's pretty easy to splice a couple wires into the harness.
Wire it this way:
3 Yellow from stator -> external RR input
1 Black RR ground -> Engine block. (If your new RR has no black wire, this ground is the metal RR housing and must be grounded to engine block using a wire or mounted to a grounded metal plate.)
1 Red RR output -> Through 15A fuse to battery positive (or positive in harness, close to battery).
Of course, replacing the MPEM is also an option, the replacement needs to include a programmed lanyard to work.
I would probably bypass the internal RR(remove BATT fuse) and install an external RR such as the one used for the 951DI or 787RFI Also, there are kits available for converting to external but it's pretty easy to splice a couple wires into the harness.
Wire it this way:
3 Yellow from stator -> external RR input
1 Black RR ground -> Engine block. (If your new RR has no black wire, this ground is the metal RR housing and must be grounded to engine block using a wire or mounted to a grounded metal plate.)
1 Red RR output -> Through 15A fuse to battery positive (or positive in harness, close to battery).
Of course, replacing the MPEM is also an option, the replacement needs to include a programmed lanyard to work.
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keithjohnson49
New Member
Just to follow up on what was wrong, it may help another newbie who has the same problem. Turns out there was a small piece of metal in the mag cover that found its way between the stator and flywheel and was shorting it out. It still passed all the continuity tests, btw. Cleaned it out, put it all back together and its running fine. I appreciate everyone's help.
Glad you found the issue. Things like this can drive you nuts.
Sportster-2001-951C-Stock
Well-Known Member
Good job troubleshooting.
You can test the diodes and SCR switches in the RR as well, to see if they're shorted. If none are shorted, that could indicate the exact problem you discovered (intermittent stator short). There are no other high current paths to ground through active components in the charging system.
You can test the diodes and SCR switches in the RR as well, to see if they're shorted. If none are shorted, that could indicate the exact problem you discovered (intermittent stator short). There are no other high current paths to ground through active components in the charging system.
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