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Glow plug problem

Discussion in '1982-Present GM Diesel' started by 84CUCV, Aug 18, 2002.

  1. 84CUCV

    84CUCV 3/4 ton status Premium Member

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    I put a new GP relay on my dads 1008 w/new GP and it is a few days later and all the plugs where shot and two where a pain to get out. They dont even have 80 miles on them. Any ideas what this could be? Thanks Mike
     
  2. Tybee

    Tybee 1/2 ton status

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    Must be staying on to long, or all the time. What glow plugs did you use?
     
  3. 84CUCV

    84CUCV 3/4 ton status Premium Member

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    i used gp that I got of I guy where i live. He works at the navy base and sold me a 6.2 and mess load of other parts. I found the gp in a box they say 272 on them an then there is wellman 68a43go70 and that is it. Could it be that I was sold the wrong relay? I would need a 12v relay because the gp are 12volt?
    Thanks MIke
     
  4. DieselDan

    DieselDan 1/2 ton status

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    THE biggest problem with the CUCV series was the gglow plug set-up. Because of the amount of amperage the GP need the GPs are fed 24V from both batteries. But the GPs are actually 12V, voltage is reduced by the two ballast resistors on the firewall. Unfortunatly, when one plug dies the volt directed to the survivors is now increased (Ohms Law). Another plug craps out and more voltage is available. Soon they're all dead.

    Check your voltage at the relay when the system cycles: 24Vs into the relay (GPs off) 12V when the relay closes (GPs ON). We 're talking battery voltage here (+/-) but if you're getting 14+ volts you've got at least one dead plug.

    So yes the relay/solenoid is 12V (switched by 12V) - nothing special off-the-shelf-item.
    I'ld have to check your part numbers, but they're probably the correct ones. HMMWV use a different terminal. Check resistance on them (thread to terminal), infinate=toast. /forums/images/icons/wink.gif
     
  5. jeffro

    jeffro 1/2 ton status

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    I beg to differ. In a parallel circuit the voltage at each plug will remain the same. An easy way to test the plugs with a test light is to unplug each one, touch the plug terminal with a test light connected to the pos. battery terminal. Failure to light will readily show the bad plugs. I don't know didly about the 1008, but if you feed 24V to a 12V plug the smoke will escape from them. We all know that once the smoke escapes from an electrical part, it will no longer function.
     
  6. 84CUCV

    84CUCV 3/4 ton status Premium Member

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    thanks for the help guys Mike
     
  7. DieselDan

    DieselDan 1/2 ton status

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    Let me try to explain Jeff. The Ballast resistors work in conjunction with the resistance from the glow plugs. When no GPs are on, there is 24V measured at the relay. When the GP cycle ON the resistance of the GPs (in conjunction with the ballast resistors) brings the voltage down to 12V.
    When you start loosing GPs the voltage will increase, ultimately back to 24V (no load). It's not a simple parallel circuit, that damn ballast resistor changes everything!

    Maybe some can explain this better than I. Trust me on this. I've been working on CUCVs since 1986. /forums/images/icons/grin.gif
     

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