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CUCV Glow Plug Voltage

Discussion in '1982-Present GM Diesel' started by rivermtnman, Dec 17, 2005.

  1. rivermtnman

    rivermtnman 1/2 ton status

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    I'm burning up a couple of glow plugs(sometimes same, sometimes different ones) every time I start the truck in the past week. They seem to cycle correctly. But i have 24 volts from the resistor to the top of the solenoid. I figured I should have 12 volts there, since thats what the resistors are for. Could somebody check theirs for me? When they cycle it does drop to 12 volts under load. I just emailed SSDiesel about some 24 volt instant heat glow plugs, and may get rid of the resistors all together.
     
  2. rivermtnman

    rivermtnman 1/2 ton status

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    OK, SSDiesel has replied to my email. They are telling me to use 24 volt glow plugs and to keep the resistors in the circuit or it will burn the 24 volt gp's up. Doesnt make sense to me unless the resistors are used to limit the current to the plugs in addition to dropping the voltage to 12v. He said that on my system it will put 24volts for a few seconds before it drops to 12 volts, and thats what is burning the 12 v plugs up. I thought I read here somewhere that the newer military diesels use the 24 v system to the gp's now. And they still use resistors? I just dont want to drop another $80 for a set of plugs and maybe he has mine confused with newer military setup. Anybody have a clue?

    If I get this figured out, I may have 4 new never installed Kennedy Quick Heats cheap for you 12 v K5ers
     
  3. DieselDan

    DieselDan 1/2 ton status

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    HMMWVs run a 24V (15G) plug. Only the CUCV used ballast resistors to drop the voltage to 12V. I can't say if what SSDiesel is saying is valid or not. If I can find on old analog voltmeter this week I check to see if the voltage hangs at 24V before dropping. (On a digital it drops instantaniously).

    We're definately in an experimental area here. My guess is the 60G's would handle it and operate with the longer cycle times the CUCV uses.

    I've got fairly new Quick Heats in my (civilian) Jimmy. Wednesday I plan on checking the plugs cause I think I may have a bad one (or two) already :doah:
     
  4. rivermtnman

    rivermtnman 1/2 ton status

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    Thanks Dan,

    Yeah I've been reading some of your older post, and think I've got it figured out. Checked 3 different auto parts stores and nobody had the 60g's, but one will have them in the morning. I had bought some Autolites last year, and now believe as soon as I lose one plug, system takes out all of the Autolites. I can say the Autolites seemed to take the overvoltage better than the Kennedy's. 60g's were what was in it when I bought it.

    I'm checking with a digital Fluke, happens so fast I cant tell. My earlier post I was trying to talk myself into that the resistors would pull the voltage down, even with the solenoid open. But I kept questioning myself that until it closed would the circuit be completed. Your earlier post got me thinking right.

    The Autolites aint no big deal, they have 2 year warranty and auto parts store are replacing them and I'll trade the 2 I found down today for the 60g's. The Kennedy's hurt the pocketbook a little more. I burnt 4 outta 4 of them up in a week.
     
  5. 84CUCV

    84CUCV 3/4 ton status Premium Member

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    60gs so i ahve been useing the wrong ones this whole time. That might be why i have starting problems.
     
  6. muddog

    muddog 1/2 ton status

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    The resistor on the firewall is supposed to limit the voltage going to the relay to around 15 volts.
     
  7. DieselDan

    DieselDan 1/2 ton status

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    Maybe the key here is the resistors work in conjunction with the GPs to pull the voltage down to 12V (14V). That why one dead plug soon gives you ALOT of dead plugs. Could it be the resistance value of the Kennedy's is too low to bring the voltage down?:thinking:

    Guess we need to post some values.....

    I think I got a set of 13Gs still on the shelf at work If I can remember I'll check them.
     
  8. 84CUCV

    84CUCV 3/4 ton status Premium Member

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    I think dieseldan is right. From what i remember, never thought of it.
     
  9. rivermtnman

    rivermtnman 1/2 ton status

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    Put the 60g's in today and she's purring like a kitten.... OK I dont think that goes with a diesel, lol, but she's runnin. I thought I ohm'd one of the good Kennedy's and it was .8 or .9 ohms, but not 100% sure. I'll try to remember to check one tomorrow and post up.

    Dan, what about a set of the 13g's and take the resistors out? Just a thought, not that I would consider it unless the resistors went out, but still think i could pick up a resistors cheaper, than a new set of plugs. Or would it be more involved?
     
  10. DieselDan

    DieselDan 1/2 ton status

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    You mean the 24V 15Gs used on HMMWVs?

    I would think this would work. (Dropping the resistors and modifying the GP harness terminals) As a matter of fact I could never understand why the Army didn't modify (as in Modification Work Order)it's inventory of CUCVs like that. Guess they lost interest :haha:
     
  11. 84CUCV

    84CUCV 3/4 ton status Premium Member

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    Are 60gs the ones that mushroom?
     
  12. imiceman44

    imiceman44 1 ton status

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    The 60G's are the latest plugs from AC delco that don't muchroom, but take longer to heat up.
    They are the safest but most times on a civilian model in cold weather might not have enough time to heat up to proper range.
     
  13. DieselDan

    DieselDan 1/2 ton status

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    OK, checked a couple of new 13Gs today. 'Got 1.3 ohms each. I'm not an electrical engineer so I don't know if this is a profound difference or not. I just know the resistors -in conjunction with 8 working GPs- drop the battery voltage to about half.

    I didn't find a anolog multimeters in our shop (most everything was left in Iraq); so I couldn't check the "response" of the ballast resistors. I think my neighbor may have an old one lying around, but I won't be back in the shop 'til next tuesday.

    PS. 13G's (& 15G's) WILL mushroom sometimes when they go. The Army hasn't seen fit enough to purchase a PTC (positive temperature control) glow plug like the 60G's :mad:
     
  14. rivermtnman

    rivermtnman 1/2 ton status

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    Sorry meant the 24v 15g's.

    I checked the Kennedy's with a Fluke 87 III, and all 4 were different readings, .7, .8, .9, 1.0 ohms. That low of resistance probably need something a little more accurate.

    One of the old 60g's that came out of my truck, the tip swelled to the point it was a snug fit coming out.
     
  15. maynardogle

    maynardogle 1/2 ton status

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    I just went through all the glow plugs on my 84 K/5 Silverado. After reading everything you guys had posted, I bought 60Gs and did the install. Afterwards, I unhooked all but 1 and installed a meter in the primary relay circuit. With 11 volts, that single new 60G plug drew almost 14 amps. I removed the meter, installed a 1 ohm resistor and repeated the test. The 1 ohm resistor dropped the voltage down to about 7 volts confirming that a new 60G is about .8 ohms. All eight of them is a lot of amps.
     

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