Electrical issue

[rusty nail]

I am looking for someone to help diagnose an electrical issue. 1994 speedster. Right side motor starts and runs. Left side motor starts, but no spark. I opened up the electrical panel and the fuse for the "mpem supply port" fuse was missing. I installed a 5a fuse and it blew right away. what are the steps to find out why the fuse is blowing. can someone walk be through this? should i unplug the ignition coil, or the amplifier and see if the fuse holds? I just purchased this boat so i do not have a history of why the left side motor no longer runs.

 

[rusty nail]

is someone able to list all the possibilites that could trip the fuse which is separate from the starting system (because that works and functions). ignition coil, amplifier(is this a dedicated part for both motors so if one motor works the amplifier is fine?), is there something on the board itself that could be shorting, etc?

 

[rusty nail]

should i unplug the stator? could this pop the mpem fuse?

 

[chipskittles]

5a fuse pops immediately may be a blown diode in the MPEM. They fail due to people jump starting the batteries. Should not ever jump start a seadoo unless it's an emergency. It's fixable if you are comfortable digging potting compound out of the MPEM and soldering a new diode in. Otherwise your cheapest fix is running two PWC MPEMS, one for each motor.

Of course I would disconnect any peripheral components like the stators, DESS if a 94 has it, and see if it still blows first. Basically everything but battery power.

 

[rusty nail]

this is great! thanks. If i unplug everything, source the issue as the mpem, are there videos or step by step photos on how to find the blown diode (or will this be obvious)? and what size diode is required to replace? I will be going back to my grade 9 electronics class to repair this board. I have a soldering iron and i think even a solder sucker. Should i get help for this or should i try tackling it?

 

[chipskittles]

This thread is where I saw the fix:
'95 Speedster MPEM Repair 278-000-601 - 5A Fuse

it's got the part number for the diode you need too, it's the kind that automotive alternators use, pretty big. I hate potting compound, it seems no matter how careful and patient you are you still end up damaging something. Only you know your capabilities, but from what i have seen a 94 boat mpem is pretty much unobtainable for a reasonable price so I would sure give it a try no matter what don't just chuck it.

 

[alkiseadoo]

If you do need to upgrade the mpem I just had Nick at Westside complete one for my 2 engine challenger was very pleased with the result.

 

[rusty nail]

this is great....i am just waiting for the administrators from PWC today to let me have access to the photos in my account. I was just trying to find if the diode, once exposed in the mpem, can be tested in place, or does it need to be removed from the board to get an accurate reading. It would be nice to know for sure (i know the hard work of removing the potting would have been done) before snipping the diode off the board.

 

[rusty nail]

also, if i post a photo of the board can someone help me locate where to begin "digging" for the diode in question?

 

[chipskittles]

From what I have seen the diode is always near the 5a fuse. Is your mpem different from the 95 mpem in the link? I would expect 94 and 95 to be pretty much identical.

Diodes are generally tested out of circuit. Sometimes they can be tested in circuit in cases of a bridge setup but most circuits have capacitors and other diodes so this won't necessarily work. You would just have to try it first I guess and if it's not clear that it's working then you would pull it out of circuit to verifiy.

 

[rusty nail]

here is the photo of the mpem and the fuse that keeps blowing has been removed in the photo. there is a small "bump" in the potting if you draw a line between the fuse in question and the 20amp fuse(yellow) . could that be it? or should i go more towards the big capacitor?

 

[rusty nail]

also, by looking at the photo, which red wire should i apply 12volts now that i have removed the mpem from the boat i would like to check one last time that it is blowing that same fuse.

 

[chipskittles]

So the link from PWCtoday with the 95 mpem, yours looks virtually identical The relay is a different brand but the layout of connectors and fuses is the same, I would start digging in the same spot,.

The easiest way to determine wiring is to look at the wiring diagram for a seadoo sportster or speedster through 97, they are all going to be very very close. Or reconnect it in the boat and follow the wires back to the battery.

 

[IDoSeaDoo]

wait, hang on. Before we determine that it's the MPEM, it can still be a shorted rectifier or shorted pick up coil. My 97 GTI had some salt water in the mag chamber and it was blowing an MPEM fuse every time. Needed a new pick up coil.

Now IF you have water in that part of the engine, you absolutely must figure out how it got there. I must have had some sort of cooling water leak, becaues my water somehow got not only into the mag chamber, but also into my crank bearings at the front, and left me stranded when the motor locked up. So take off your mag chamber and have a look. I'm 70% sure this is also where the MPEM gets it's ground from, so (again 70% sure) you can figure out which wire gives it ground and give it yourself and see if maybe it doesn't blow the fuse.

 

[rusty nail]

i unplugged the mag from the mpem and it still blew the fuse, so i am assuming it cannot be that....correct? I have now pulled the mpem from the boat and want to do a bench test before i start digging, can you help me determine which is the power and ground lead coming off the mpem? I will give it power on the bench and attempt to install a fuse one last time, and this should confirm the short is in the diode? advice? Thanks.

 

[rusty nail]

also, can the mag be opened up and checked without pulling the whole motor out of the boat?

 

[rusty nail]

after getting information from a number of sources, i have begun to piece together some problems. Here is my now mpem with which i believe is correctly fused.(after looking at a few wiring schematics and older and newer speedster manuals). i used my meter on the diode setting and put the red lead to the ground and black lead to each of the 5 amp fuses. The port side is showing .000 and the starboard side is .684 indicating the port side diode has a short and is bad. i will at some point try to repair the mpem and in the spring still pull the port engine from the boat and make sure the diode was not destroyed from a magneto issue.

 

[IDoSeaDoo]

Bummer. Good luck depotting it. That's a pita to say the least. Keep an eye out for a similar mpem. They come up now and then. Also, yes, you can open up the mag without pulling the motor.

 

[rusty nail]

here is the board

 

[chipskittles]

Looks solid. You can cover up the scratches with conformal coating, or nail polish would be ok too i would think

 

[Sandman251]

You have to be careful when you look at information for Speedster electrical issues. The 94 Speedster was basically a science experiment for Bombardier. Not even all 94's are the same. Do you have the 4 wire mag set up? You can really Chase your tail on a 94. 95 and up different story.

 

[rusty nail]

Good news, after a long wait for the diode to be shipped it has arrived, been installed on the board, and reinstalled in the boat......and we have spark!!!! i put the plugs back in and now it seems the starter is quite weak and does not turn the motor fast enough under compression. I am guessing this is why the diode blew? The former owner thought it was a weak battery and boosted the system with jumper cables and fried the diode and what really was the problem was a bad starter. Anyways, time to dig into the boat and replace the starter.....good times.

 

[rusty nail]

when i get a chance i will take a photo of the diode now installed. I simply cut the legs of the old diode and made the new one stand taller without removing the old diode completely from the board. This way i did not have to cut the back of the mpem apart to remove the legs out of the board and also if the replacement diode goes again it will be a simpler fix

 

[noooby]

Most excellent! I look forward to a photo of two. Good job. As the owner of a 94 Speedster project with suspect wiring repairs, I fully expect to have to do a diode replacement.