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How does this work.....

Discussion in '1982-Present GM Diesel' started by 84CUCV, Feb 16, 2006.

  1. 84CUCV

    84CUCV 3/4 ton status Premium Member

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    Just saw on my M1028 there is no resister on the back wall. So how does these truck start? i thought that was needed to drop the volts or something like that. any idea? here is a few pics thx

    DSC02208.JPG

    DSC02209.JPG

    DSC02210.JPG
     
  2. afroman006

    afroman006 1/2 ton status

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    You turn the key and it go vroom vroom.













    Sorry, I couldnt resist.:haha:
     
  3. 84CUCV

    84CUCV 3/4 ton status Premium Member

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    I thought someone was going to do that.....
     
  4. jp0863

    jp0863 1/2 ton status Premium Member

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    the only thing that runs on 24 volt is the starter. the wire running across the firewall is 12 volt run from one terminal on the batteries. the glow plugs run in sequence so that it drops the voltage from 24 to 12. thats why if one glow plug goes out, it tends to take out the rest as they are running on more and more voltage as they go out. i have never experienced this myself and am in no way an expert. this was how it was explained to me by the guys that work on these rigs. i have a local transportation division near me, they have been a valuable source of info.
     
  5. 84CUCV

    84CUCV 3/4 ton status Premium Member

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    Wish i had some guys like that down here. all i hear is the wireing on these trucks sucks. thx mike
     
  6. DieselDan

    DieselDan 1/2 ton status

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    There's nothing wrong with the wiring on a CUCV, ya just gotta know what you're looking at :wink1: .
    Somebody already modified your GP harness. It might work OK, or maybe not. The only issue you now have is (I assume) all of your GP voltage is comming off just one battery. That is alot of amperage for one battery. Now as you should know; CUCVs have a split voltage system. Each battery has it's own altenator (a good thing). Only the starter, and the Glow Plugs (orginally) utilize both batteries for 24V.

    I would run yours like you got it, unless you start having problems with the GP circuit (like not getting the GPs hot enough or killing your battery). I would suggest you rotate you batteries between the two mounts, just to even out their usage. That's something we used to do to the CUCV's to get the longest life out of the batteries. :waytogo:
     
  7. 84CUCV

    84CUCV 3/4 ton status Premium Member

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    OK thx diesel dan i got it
     
  8. 84CUCV

    84CUCV 3/4 ton status Premium Member

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    dieseldan, any chance you can give me idea what the motor pool did to this truck? Just put on a new relay. Now this one will not start either.:( :confused: any ideas? thx for your time
     
  9. DieselDan

    DieselDan 1/2 ton status

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    Well, I'm assuming that because the ballast resistors are gone they are drawing 12V power off just one of the batteries as opposed to the original set up of using 24V (both batteries) then reducing the voltage back down to 12V to the glow plugs.

    What's your truck doing? Is your relay switching (on/off)? Is your voltage dropping from 24V to 12V when the relay clicks on? It doesn't take much for a glow plug to crap out then all the others to follow in a few more starts (glow cycles).
     
  10. 84CUCV

    84CUCV 3/4 ton status Premium Member

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    That would be the first palce to start i think and no now that i think about it. the relay is not doing a thing. thx dieseldan
     
  11. muddog

    muddog 1/2 ton status

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    THe blue wire should be on the upper little post and the red wire on the lower little post.
     
  12. 84CUCV

    84CUCV 3/4 ton status Premium Member

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