and another roadblock on my rebuild.....no spark

[JuliusCaesar]

1993 XP 657. Put engine in, fresh battery, all hooked up and ready to go. Put my spark test on the plug wire and pushed the start button. No spark. Took tether off and it wouldn't turn over so i know that works. hooked tether back up and pushed start button and then used kill switch on bar and it stopped turning over. K, that works. Hmmm, opened up electrical box and plugged ohm meter to stator power and cranked. 13.7v. nice and fresh. SO, don't think stator is issues as of yet.

Pulled MPEM and went to my manual. Tested all wires with lowest resistance i could on my meter and there were some dead spots.(ie rectifier) and one solenoid seemed to be incorrect.

What confuses me is that the previous owner says it worked last year then when he went to start it this year it wouldn't start. He thought it was the RV shaft/valve. Now i'm thinking it was MPEM all along. Doesn't make sense to me that a unit that sits over the winter all of a sudden has a crappy MPEM. He could have been lying to me, but i don't think he was just based on how he presents himself.

Now to find a good 5 wire MPEM.....

 

[etemplet]

Are you sure it is the MPEM. My 1996 SPI 587 would turn over but not fire and all I had to do was remove and reinstall the cap... and she fired right up. Another poster had the same issue and that solved his problem as well. Sounds like you tested everything so just making sure. Hate to see people spend money they don't need to spend. I'll take a look at see what I have regarding MPEMs. I don't go back that far but one of these might work for you.

 

[JuliusCaesar]

i trimmed off 1/4" on each wire and redid the boot. Still nothing. This MPEM is the 278000305 93XP but 278000071 94XP will work as well. These have the white wire instead of the red/black. and i think that these are the only ones that work.

 

[DougtheSlug]

Isn't it possible to bypass the MPEM by unhooking it to test for spark? I know it works on the 580 motors of that generation, they used the red/black wire you mention that could be disconnected for testing.

 

[JuliusCaesar]

Isn't it possible to bypass the MPEM by unhooking it to test for spark? I know it works on the 580 motors of that generation, they used the red/black wire you mention that could be disconnected for testing.

I did unhook that wire. In my MPEM the red/black was changed to white on the 93 and 94 xp. No spark when that was unhooked. I'll post up my findings on my metering of my MPEM when i have a moment.

 

[DougtheSlug]

If there's no spark when the module is unhooked, that would point to the coil/cdi being at fault. It still needs to be connected of course, but that's my understanding.

 

[JuliusCaesar]

If there's no spark when the module is unhooked, that would point to the coil/cdi being at fault. It still needs to be connected of course, but that's my understanding.

i get resistance at the coil when the plug wires are unhooked. 5 ohms i think it was...not sure what the correct resistance should be.

 

[DougtheSlug]

Ignition coil resistances: Primary winding Black with White/blue = 0.23-0.43 ohm Secondary winding end of each spark plug cable (caps removed) = 5.85-6.50 k ohms.
The shop manual mentions that an ignition coil with good resistance tests can still be faulty. Using a known good coil is still the best test.
Since the 93 XP uses a different system than the 580's, there is another module involved so I don't know if the test I mentioned before applies.

 

[JuliusCaesar]

Thank you for the reply. Did some more testing here on the stator according to my manual and all checks out with range.

Redid the MPEM and some numbers just don’t work. Either too low or non existent and my multi meter goes up to 20M ohms. So it should all be in range.

 

[JuliusCaesar]

image attached of readings

 

[JuliusCaesar]

just a follow up on this. I went through another test in the manual for the magneto, coil and module. Magneto ohms out perfectly to the book but the module doesn't either does the coil Module has white/blue and black wire going to the coil and they are open...no resistance. Coil resistance comes out very high. I have to be on 20M ohms to get any reading where it should be in the 5.5k ohm area. SOOOO, thinking i'll start with grabbing a use module and coil off ebay first then working my way back to the MPEM. When the MPEM white wire (93/94xp only) is pulled apart, i read that i should get spark and if not, then look to mag or coil. Well, i didn't get spark, so i dug deeper and the ohm readings are not where they need to be. Now i wonder if the OP had tried boosting this PWC in the spring to get it started and killed some of the electronics........

 

[JuliusCaesar]

UPDATE on this and the problem WAS the MPEM. Picked up a used one from a 1994 on eBay and all is working perfectly again.