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Bypassing 1999 Challenger 1800 Mpem
- Thread starter WHYMpem
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XP 787
Active Member
Correct, you cannot bypass but you can use 2 mpems from skis. This also requires you to use 2 dess posts/keys.
Skip to 2:45 https://m.youtube.com/watch?v=XUL2hgHi-9k
Hit up [MENTION=41828]Minnetonka4me[/MENTION] for parts.
Skip to 2:45 https://m.youtube.com/watch?v=XUL2hgHi-9k
Hit up [MENTION=41828]Minnetonka4me[/MENTION] for parts.
XP 787
Active Member
I have no idea how it is done, but it is possible to do.
BoLongo
Active Member
I am contemplating an MPEM hack for my 1999 Challenger. There are three micro controllers in the MPEM; one controls the DESS and the other two control the ignition systems for each engine. In my case the micro controllers that control the starboard engine has gone bad. If I were to hack the CDI on each engine and run them parallel, I might be able to get away with it. I’m looking into my options and I will post what I find. If you have lost the micro controller that controls the DESS it might not be possible.
BoLongo
Active Member
I'm going to buy this CDI Box and see if I can wire it parallel with my current MPEM.
http://r.ebay.com/I5wPrB
http://r.ebay.com/I5wPrB
This site contains eBay affiliate links for which Sea-Doo Forum may be compensated.
BoLongo
Active Member
From the 1999 Shop Manual:
Multi-Purpose Electronic Module (MPEM) The MPEM has 3 micro-controllers inside of its sealed case. One is basically responsible for the DESS (Digitally Encoded Security System), interpreting information, distribution of information, and as a timed/untimed power source. The 2 others are used to manage the ignition system (one for each engine). A relay is used to prevent discharge of the battery, through the ignition system, when the craft is not running. The relay is in the MPEM. The DC-CDI system within the MPEM receives the input from the trigger coil and signals the ignition coil when to fire. It also has the RPM limiter function built into its circuitry, as well as the ignition timing curve. Ignition Coil The ignition coil steps up the voltage input from the DC-CDI system and the end result is firing of the spark plugs. The coil is housed in the electrical box.
Multi-Purpose Electronic Module (MPEM) The MPEM has 3 micro-controllers inside of its sealed case. One is basically responsible for the DESS (Digitally Encoded Security System), interpreting information, distribution of information, and as a timed/untimed power source. The 2 others are used to manage the ignition system (one for each engine). A relay is used to prevent discharge of the battery, through the ignition system, when the craft is not running. The relay is in the MPEM. The DC-CDI system within the MPEM receives the input from the trigger coil and signals the ignition coil when to fire. It also has the RPM limiter function built into its circuitry, as well as the ignition timing curve. Ignition Coil The ignition coil steps up the voltage input from the DC-CDI system and the end result is firing of the spark plugs. The coil is housed in the electrical box.
BoLongo
Active Member
I can't find an MPEM for a 1998 -1999 Challenger or Sportster 1800 right now.
I am contemplating buying another Challenger 1800 and robbing parts than donating the hull to charity. I hope that is not the way I have to go.
I bought one of the aftermarket XP CDIs, it will be here next week. I'm hopeful it will work wired parallel with my current MPEM.
Everything works on my boat, my issue is the ignition system is causing piston failure on the starboard PTO cylinder. My fix with the XP CDI wired parallel would not work for someone who has an MPEM that is not allowing their engines to start. but the XP CDI units could be used to get the engines running but it would require a lot of rewiring.
Eventually someone will come up with a solution to the 1998-99 MPEM. There are not many used MPEMS left and as the price climbs someone will make money developing a solution, but that does not help those of us with bad MPEMs this season.:facepalm:
I am contemplating buying another Challenger 1800 and robbing parts than donating the hull to charity. I hope that is not the way I have to go.
I bought one of the aftermarket XP CDIs, it will be here next week. I'm hopeful it will work wired parallel with my current MPEM.
Everything works on my boat, my issue is the ignition system is causing piston failure on the starboard PTO cylinder. My fix with the XP CDI wired parallel would not work for someone who has an MPEM that is not allowing their engines to start. but the XP CDI units could be used to get the engines running but it would require a lot of rewiring.
Eventually someone will come up with a solution to the 1998-99 MPEM. There are not many used MPEMS left and as the price climbs someone will make money developing a solution, but that does not help those of us with bad MPEMs this season.:facepalm:
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BoLongo
Active Member
My current MPEM thinks everything is fine but the microprocessor controlling the Starboard CDI is sending faulty information to the coil box. The plan is to keep everything hooked up except the single wire that tells the coil to fire.
I’m going to mount the 1996 XP 787 single engine MPEM next to the original MPEM
1. Hook up the power and ground from the battery to the after market MPEM
2. Tap into the wire that is coming from the magnetic pick up in the Mag housing.
3. Run a wire from the Aftermarket MPEM to the coil to control when the spark plugs fire.
4. The final piece of the puzzle will be where to tap into the power supply after the DSS post, so it will kill power to the aftermarket MPEM which will kill the spark to the engine.
The original MPEM will be used to start the engines, DESS and tachometers.
If this works I will buy a second unit for the port engine.
This fix should also work for any 1998/99 MPEM without a spark.
Stay Tuned!
I’m going to mount the 1996 XP 787 single engine MPEM next to the original MPEM
1. Hook up the power and ground from the battery to the after market MPEM
2. Tap into the wire that is coming from the magnetic pick up in the Mag housing.
3. Run a wire from the Aftermarket MPEM to the coil to control when the spark plugs fire.
4. The final piece of the puzzle will be where to tap into the power supply after the DSS post, so it will kill power to the aftermarket MPEM which will kill the spark to the engine.
The original MPEM will be used to start the engines, DESS and tachometers.
If this works I will buy a second unit for the port engine.
This fix should also work for any 1998/99 MPEM without a spark.
Stay Tuned!
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dmiles
Member
Fingers crossed, will be following closely!
2x2smoke
Member
If your plan doenst work, why not just treat the motors as completely distinct entities? It would lose some features of the mpem like the single lanyard and the buzzer functions.
buy two aftermarket generic CDI units http://www.ignitech.cz/en/vyrobky
rewire so you have two starter buttons, two kill buttons, maybe even a master kill lanyard
perhaps two separate reg/rectifiers, two proper temperature gauges
I bought a cdi from the czech guy to revive a motorcycle that was otherwise junk because the cdi was impossible to find. He offers tuneable units so you might be able to match the ignition curve, rev limiter etc
These are just simple engines, go old school on them if you have to, outsmart them
buy two aftermarket generic CDI units http://www.ignitech.cz/en/vyrobky
rewire so you have two starter buttons, two kill buttons, maybe even a master kill lanyard
perhaps two separate reg/rectifiers, two proper temperature gauges
I bought a cdi from the czech guy to revive a motorcycle that was otherwise junk because the cdi was impossible to find. He offers tuneable units so you might be able to match the ignition curve, rev limiter etc
These are just simple engines, go old school on them if you have to, outsmart them
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mobilefleet
Member
I have a 97 challenger 1800 with no spark on one engine due to mpem. I'm interested to see if that works, but I already bought a parts boat for mine and will be taking the mpem off it, and selling the rest including good engines and all other parts. If anyone needs anything I will be posting this once it's been stripped down.
BoLongo
Active Member
Got the 97 MPEM and CDI today but the hack is more complicated than I expected. I am returning both.
I just bought the MSD Enhancer Ignition 4255 which will work in parallel with my current MPEM. The unit runs $425 each, one for each engine. The MSD is programmable so I can up the rev limiter to around 7500 and see a couple extra MPH on the top end.
http://www.msdperformance.com/products/powersports/watercraft/parts/4255
I will do a write up when I get it the end of next week.
I just bought the MSD Enhancer Ignition 4255 which will work in parallel with my current MPEM. The unit runs $425 each, one for each engine. The MSD is programmable so I can up the rev limiter to around 7500 and see a couple extra MPH on the top end.
http://www.msdperformance.com/products/powersports/watercraft/parts/4255
I will do a write up when I get it the end of next week.
BoLongo
Active Member
The 1996 Sea Doo 787 XP electrical system runs an MPEM and a separate CDI unit. It was my hope that I would be able to use the separate CDI unit with my existing MPEM. The problem is the 1996 CDI unit uses the MPEM for the advance timing curve. So I have to use both the MPEM and the CDI unit which can be done but there is a better solution with the MSD Enhancer which it is a standalone CDI. The Enhancer provides better timing throughout the advancement curve and is programmable.
The cost for the 1996 Sea Doo 787 XP aftermarket MPEM and CDI unit is about $375.00 and requires some complicated rewiring; the MSD Enhancer runs $425.00 with simple wiring and some performance enhancements.
The MSD Enhancer can be used with an MPEM with a no spark situation and it can be wired in as a replacement for the MPEM but it would require rewiring the boats electrical system.
The cost for the 1996 Sea Doo 787 XP aftermarket MPEM and CDI unit is about $375.00 and requires some complicated rewiring; the MSD Enhancer runs $425.00 with simple wiring and some performance enhancements.
The MSD Enhancer can be used with an MPEM with a no spark situation and it can be wired in as a replacement for the MPEM but it would require rewiring the boats electrical system.
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mobilefleet
Member
cool. awaiting the writeup on this, with pics and /or wiring info so we can all learn how to do this if needed in the future for our boats. Now that BRP stopped jetboats in 2011 parts will be getting harder and more expensive to come by, so mods are the only hope in some cases.
BoLongo
Active Member
The MSD 4255 Ignition Enhancer has been used on racing skis for years. Not many people are willing to drop $900 on an updated ignition system for a boat, but with a USED MPEM in the $1700 range; a brand new ignition system for $900 is a bargain.
The MSD 4255 Ignition Enhancer really shines on a built motor, but it will improve the performance of a stock motor. I have read that some people have had success raising the rev limit to 8000 RPMs on a stock 787 and picked up about 10 MPH on the top end. Others have said that the stock 787 will top out around 7800 RPMs without a rev limiter on the water (impeller pitch will affect RPMs). These results were on skis so I’m not sure what I’ll get out of a boat.
The MSD 4255 Ignition Enhancer really shines on a built motor, but it will improve the performance of a stock motor. I have read that some people have had success raising the rev limit to 8000 RPMs on a stock 787 and picked up about 10 MPH on the top end. Others have said that the stock 787 will top out around 7800 RPMs without a rev limiter on the water (impeller pitch will affect RPMs). These results were on skis so I’m not sure what I’ll get out of a boat.
Last edited by a moderator:
BoLongo
Active Member
You got to love California. C.A.R.B. (State EPA) does not allow products that modify an engine to be shipped to a California address without licensing through C.A.R.B. I had to jump through some hoops but it is now on its way to my home in California.
I want to keep my current MPEM hooked up so my gauges and electrical system keep working.
Here is the wiring diagram of the MSD Enhancer CDI.
1. I will rewire the (grey wire) to the tachometer; I will cap the tachometer wire from the MPEM
2. I will tap (tee) into the + (yellow wire) & - (green wire) trigger from the magneto, I want to keep these wires going to the stock MPEM so it knows when the engine is running.
3. I will rewire the (blue wire) thermo sensor to the MSD Enhancer; I will cap the wire from the MPEM
4. I will tap (tee) into the ground (black) wire at the MPEM location
5. I will rewire the (orange wire) to the coil and cap off the wire from the MPEM that was going to the coil.
6. I will tap (tee) the (red wire) into a switched hot wire and add a 15 amp inline fuse.
7. I will tap (tee) the ground wire from the DESS Post into the (purple & white wires)
Here is what will change with this set-up:
I will use the current MPEM and start buttons to start the engines. The start button will no longer be able to kill the engine because the stock MPEM will no longer control the coil; the way to kill the engine is to pull the key from the DESS post.
I hope that the current MPEM and the two MSD Enhancers can get along. I should find out this weekend.
I am sure that the MPEM was bad when I bought the boat. I remember when I came to look at the boat the seller was jumping the boat with his truck; back then I had no idea that jumping the boat’s battery could kill the MPEM.
I want to keep my current MPEM hooked up so my gauges and electrical system keep working.
Here is the wiring diagram of the MSD Enhancer CDI.
1. I will rewire the (grey wire) to the tachometer; I will cap the tachometer wire from the MPEM
2. I will tap (tee) into the + (yellow wire) & - (green wire) trigger from the magneto, I want to keep these wires going to the stock MPEM so it knows when the engine is running.
3. I will rewire the (blue wire) thermo sensor to the MSD Enhancer; I will cap the wire from the MPEM
4. I will tap (tee) into the ground (black) wire at the MPEM location
5. I will rewire the (orange wire) to the coil and cap off the wire from the MPEM that was going to the coil.
6. I will tap (tee) the (red wire) into a switched hot wire and add a 15 amp inline fuse.
7. I will tap (tee) the ground wire from the DESS Post into the (purple & white wires)
Here is what will change with this set-up:
I will use the current MPEM and start buttons to start the engines. The start button will no longer be able to kill the engine because the stock MPEM will no longer control the coil; the way to kill the engine is to pull the key from the DESS post.
I hope that the current MPEM and the two MSD Enhancers can get along. I should find out this weekend.
I am sure that the MPEM was bad when I bought the boat. I remember when I came to look at the boat the seller was jumping the boat with his truck; back then I had no idea that jumping the boat’s battery could kill the MPEM.
Last edited by a moderator:
BoLongo
Active Member
The rest of the story... Yes, I set up the bypass and it worked perfectly. The boat ran 3-5 MPH faster and had more power out of the turns. This is a valid solution for anyone with a MPEM that turns over the engines but will not create a spark. The cost was roughly $900 but that is far cheaper than a used MPEM plus the increased speed and power. but be careful with the settings, you can quickly burn up an engine if the settings are too advanced for a stock engine. I mounted two MSD 4255 Ignition Enhancers to a plastic board and mounted them next to the MPEM. I soldered in the slices, adjusted the settings and the boat is running great! I had to add a kill switch to the dash because the DESS post would not kill the engine (DESS is part of the MPEM).
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Hi BoLongo, I have the same boat with only one engine with no spark. Sounds like my solution. what did you do to kill the engines?
Perfect. Thanks, why did you get rid of the boat? Moved on to bigger and better things?
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