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cat ecm showing 10.5 volts

Discussion in 'Peterbilt Forum' started by easttxtrucker, Dec 13, 2011.

  1. Dec 13, 2011 #1
    easttxtrucker

    easttxtrucker Bobtail Member

    12
    0
    Dec 13, 2011
    gladewater, tx
    0
    I have a 97 379 Pete which had a 3406 475hp motor which I had to rmove due to the crank was broke at the first cylender which I thought was a fuel issue at first. I removed motr and cut some wires in process. Matched up and fixed wires once out of way. Went in with another 3406 550hp motor. Kept old wiring and ecm due to being the same motor except hp. Once everything was hooked back up went to start and melted 2 batteries. The guy who did it did not put back together the way it came off. I found a diagram and now it is wired correctly. Went to start again and melted another battery. Took all wires off. Check one at a time. As I got to the ECM ground wire (pin 5) I found it is showing 10.5 volts on the meter. Is this wire supposed to have voltage as a ground? I have pulled every wire off the fram and fixed if needed. Pulled battery wires and checked them. this is only showing volts with key on. I changed voltage regulator and no change. I unplugged alternator wires and showed no voltage. My question is: is this wire supposed to show voltage or do I have a short? If its a short where should I look? Any help would be great. I have been messing with this for a week now and yet to get truck staryed since motor was put in. Thanks
     
    easttxtrucker, Dec 13, 2011
    easttxtrucker, Dec 13, 2011
    #1
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  3. Dec 14, 2011 #2
    RJC

    RJC Bobtail Member

    23
    13
    Jul 26, 2011
    Dothan,Alabama
    0
    Have you checked all your battery cables to make sure that they are correctly connected to batteries. If so make sure they are connected to the starter right. Sounds to me like a positive wire is hooked to a ground, or a ground is hooked to a positive terminal, either at the battery or starter.
     
    RJC, Dec 14, 2011
    RJC, Dec 14, 2011
    #2
    volvodriver01 Thanks this.
  4. Dec 14, 2011 #3
    easttxtrucker

    easttxtrucker Bobtail Member

    12
    0
    Dec 13, 2011
    gladewater, tx
    0
    Yes I pulled each one and then marked them then put back in and put on correct post.
     
    easttxtrucker, Dec 14, 2011
    easttxtrucker, Dec 14, 2011
    #3
  5. Dec 14, 2011 #4
    easttxtrucker

    easttxtrucker Bobtail Member

    12
    0
    Dec 13, 2011
    gladewater, tx
    0
    Would the motor mount bolts not being put in and tightened cause this?I just saw he put bolts on one side no nuts. Other side there not even any bolts. Ivhave gone thru ever wire on this truck
     
    easttxtrucker, Dec 14, 2011
    easttxtrucker, Dec 14, 2011
    #4
  7. Dec 14, 2011 #5
    easttxtrucker

    easttxtrucker Bobtail Member

    12
    0
    Dec 13, 2011
    gladewater, tx
    0
    I answered my own question. Tightened bolts for motor mounts and still have same problem
     
    easttxtrucker, Dec 14, 2011
    easttxtrucker, Dec 14, 2011
    #5
  8. Dec 14, 2011 #6
    easttxtrucker

    easttxtrucker Bobtail Member

    12
    0
    Dec 13, 2011
    gladewater, tx
    0
    Took the wire harness at ecm and lost the 10.5 volts. I finally got ahod of a technician (I've lteraly called 30 differnt places) he told me to do this. My question now is can I take it somewhere to be looked st make sure I didn't mess the ecm up. I can't buy a new one
     
    easttxtrucker, Dec 14, 2011
    easttxtrucker, Dec 14, 2011
    #6
  9. Dec 14, 2011 #7
    RJC

    RJC Bobtail Member

    23
    13
    Jul 26, 2011
    Dothan,Alabama
    0
    I have reread your post and I am under the understanding that you have not yet been able to start the truck at all,and when you try you cook batteries. Also if the truck has not been running then 10.5 volts showing is what is in the batteries.

    I do not know if pin #5 should show any voltage, if not you probably are missing a ground wire. There should be a ground wire from the starter to the frame, and a ground wire above the starter just under the head from the block to the frame.

    I am guessing that you have either a bad starter or a wire hooked to the starter wrong. When you turn the key on everything is okay but when you hit the starter button then you are shorting the batteries. If your batteries are not hooked in series right then you will not be pulling off all the batteries, and that would overload the draw and cause the cables to get real hot and short them out.

    If by any chance your starter is locked up then when you hit the button that would also cause a short back to the batteries. Hope this helps
     
    RJC, Dec 14, 2011
    RJC, Dec 14, 2011
    #7
    volvodriver01 Thanks this.
  10. Dec 15, 2011 #8
    easttxtrucker

    easttxtrucker Bobtail Member

    12
    0
    Dec 13, 2011
    gladewater, tx
    0
    The pin 5 on the diagram is showing to be ground. Was unaware this had voltage when I first went to start it. After taking it off ground the truck cranks but wont start. I took the cables off the ecm and lost the voltage. from what I have been told the ecm may be bad so im taking it to cat to have them look. I have gone thru all the wires and triple checked were all the wires go soim guessing the ecm is messed up. I will know tomorrow for sure. I hope its nothing major. I've beencalling everywhere but no one will call me back or give me any incite. Im in texas and found a place in maryland that told me about removing the wires. I've had trouble with this truck from day one. Im gonna haul it back to previous owner and get my money back lol
     
    easttxtrucker, Dec 15, 2011
    easttxtrucker, Dec 15, 2011
    #8
  11. Dec 15, 2011 #9
    Shade Tree

    Shade Tree Light Load Member

    177
    44
    May 15, 2011
    Galloway Ohio
    0
    For you to have power on a ground wire it has to be ground wire issue. I had Peterbilt that had the same problem and it ended up being the ground wire from the engine to the frame. Once corrected it was fixed. I knew there was problems when I went to hook up ground cable to batteries and got a huge arcing sound and cables got hot immediately. You may also try slaving in the ECM from the old engine, to see if it does the same thing and starts. Make sure you ground the ECM. If it is the ECM, you can get the files downloaded from the bad ECM and reflashed into your 475HP ECM.
     
    Shade Tree, Dec 15, 2011
    Shade Tree, Dec 15, 2011
    #9
  12. Dec 15, 2011 #10
    easttxtrucker

    easttxtrucker Bobtail Member

    12
    0
    Dec 13, 2011
    gladewater, tx
    0
    Well the mechanic who swapped them out took the old ecm to the place I got it. I had to return it for the "core" for the price I got the motor. I called them and they wont let me have it. So im going to go ahead and go to cat. I've not had much luck at alll with this truck or mechanic
     
    easttxtrucker, Dec 15, 2011
    easttxtrucker, Dec 15, 2011
    #10
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