951 won't crank steady

[KevinT]

I have a 1998 XP limited with 951 engine. I can't get it started because the starter won't spin continuously but stops and starts.

If the starter does spin the engine it starts right up. But the starter will not spin the engine steadily and consistently. Pushing the start button it might spin normally for several rotations but eventually reverts to cranking a single rotation or two. Sounds horrible.

It's always done this to some degree in the nine years I've had it. Always started eventually until now and even now it starts sometimes.

Here's what I've done so far:
New battery
New solenoid
Three different starters
New Bendix
No voltage drop on cables
Beeps normally
Pulled the pump. It spins freely.

If I jumper across the solenoid secondary outputs the starter/engine cranks fast and normal
If I carefully apply 12v and ground to the solenoid primary coils the solenoid energizes and the starter cranks fast and normal
I have pulled the connector 3 from the MPEM and tested the start switch and it appears to be working well
I pierced the wires to the start switch at the switch end and shorted them together bypassing the switch and the problem remains - erratic cranking
I have continuity from MPEM connector 2 to solenoid primary coil.

Everything in the starter circuit has been tested except the MPEM

Just for grins I replaced all the fuses

It appears that the solenoid is not receiving start signal from MPEM. Is there a reed relay or something inside the MPEM that went bad?
Maybe I got a bad solenoid. I have another I may try.

Thanks for any help.

 

[POPPS]

I once had a 951 with similar symptoms,,,main engine ground from the bottom of the motor,,,at the rear..underneath the pulse fitting,,,a 17mm bolt...was the issue,,,give it a looksee....

 

[Grim]

I got the same problem with my 98 GTX LTD. I haven't figured it out either. I'm going to look at POPPS suggestions...its worth a try!

 

[SIMPLEARKANSAN]

My 2000 GTX with the 951 had an inconsistent start. I replaced the start/stop button and it will turn over every time now.

 

[Grim]

I once had a 951 with similar symptoms,,,main engine ground from the bottom of the motor,,,at the rear..underneath the pulse fitting,,,a 17mm bolt...was the issue,,,give it a looksee....

My connection is good, do you know where the other end goes. I would like to test ground at that end!

 

[Poormanracing]

Run another ground wire from battery to block.also on the mag housing there are ground wires attached with a ten mm bolt.pull the air horn on mag cyl air box and its right there.

 

[Idiotwita elec prob]

I had this problem as well and only recently fixed it I think… something else is broken and it’s a long story either way for me it was a mix up of you have to have the same rotor magneto and MPEM I had gotten a used engine and it apparently had different rotor than the original one had that matched MPEM and stator and was causing it to not spin constantly till I put the old rotor into the used engine and it fixed it what it was that caused it was the used engine had 4 tabs on the outside for speed and spark when it was only supposed to have 2 causing the engine to think it was going 2 times faster than it was making it think it had started disengaging the starter solenoid and stopping the starter then it realized that it wasn’t started and repeats the process. Now that I got that figured out though now it takes to much power causing the MPEM to momentarily lose power and stopping it and now I have the same description of problem just different cause I have no idea about.

 

[Grim]

I finally got mine fixed of this issue. It was a loose/bad connection with all/one of the wires going to the coil. I cleaned them all and when I reconnected them ( three in all I believe) I made sure they did not bunch up on top of each other, but were spread out evenly to get a good contact. She was good to go after that.