SOLVED !! Stranded 93' MCI 12 6v92 DDEC3 Wont Start

[Beachfinn]

WOOHOO !
with help from Jack, it's running. I'll post more detailed report later, but here's the short scoop. I checked the main power connector to DDEC (Two 12v red wires and 3 black grounds), these are fed directly from battery via the two fuses in the battery compartment. All checked fine. Pulled the large connector next to it (with a 1/4" screw holding it). As Jack said there should be 12V coming from the ignition switch to a pin (wire stamped with 439). No voltage; so its either the chimes switch, ignition switch, but more likely a relay in the bus rear or stop/run switch in the engine compartment. I put a jump wire from DDEC 12v feed to that pin, and voila' started right up. Drove it back to the hotel with everything normal. Now heres the biggest lesson of all: that pin wired directly from battery...the bus will not shut down even if you throw the main switch. So in essence, as long as you have 12v to the DDEC and that pin hot, it will run.

Thank you all for your help, what an awesome feeling when it fires up

[luvrbus]

It has to have the ground also,they are not as complicated as most think 2 wires and they will run.I am late to electronic control engines game but I have just about figured out where the old mechanical engines needed just air and fuel to run, the electronic engines just need a power supply and a ground to run     

[Scott & Heather]

Hey I didn't even know there were such thing as a DDEC III two stroke??


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[luvrbus]

Hey I didn't even know there were such thing as a DDEC III two stroke??


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They have a DDEC IV to work with all the other transmission,I have a 8v92 DDEC IV in my shop now 550 hp factory setting a sweet engine fwiw   

[Oonrahnjay]

They have a DDEC IV to work with all the other transmission,I have a 8v92 DDEC IV in my shop now 550 hp factory setting a sweet engine fwiw   

    Wow, nice.  I had no idea such a thing existed for road use.  Sounds very sweet indeed.

[Iceni John]

Sam,

I'm happy to hear that you found how to put 12V onto pin 439 to get the engine to run (but not stop).   I had a weird situation recently that possibly may be relevant to you.   My main 100A feed from the start batteries and starter had a very badly corroded terminal in its Class H fuse holder, so much so that the engine died when I turned on the headlights!   I had to completely rebuild the fuse holder, crimp new ends onto the cables, and while I was at it I also replaced all three Cole-Hersee solenoids because they were 25 years old and in umknown condition.   Having done all this, I now have absolutely no voltage loss whatsoever between the start batteries and the front junction box and start switch, even under load (I had almost one volt loss before!).   Essentially I have now replaced or cleaned every terminal and connection between the batteries and the DDEC, including all the grounds.   DDEC works well provided it has sufficient voltage  -  any poor connections will cause problems sooner or later.   Yes, it's tedious groping around inside the engine room to do this work, but it's still better than having everything completely die while driving.   A good VOM is definitely well worth it!

John

[Beachfinn]

And here was the issue, fuse/circuit breaker in the back electrical box. replaced with inline fuse. I'll replace with original (and the one next to it) on my next visit to MCI (need windshield). Been living in the bus and traveling 3K miles since then, I'll update my build thread soon with all the great stuff that has happened and been done.

[blue_goose]

One more question, have you found the check and stop engine lights?  They are there somewhere.

Jack