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Thread: Glow plugs died randomly!! Please help

  1. #1
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    Mar 2021
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    Default Glow plugs died randomly!! Please help

    I've already ran through the Facebook forum and stumped everyone there, so I'm hoping to have more success on here.
    2000 Chevy 6.5 turbo diesel truck has always started always ran glow plugs have always worked even though I was getting a glow plug circuit malfunction code but the glow plugs always worked always started never had a problem with them I never understood why I was getting that code.
    I changed nothing the truck sat for 2 or 3 weeks through winter -10 pretty cold and one day went out there no glow plug light on the dash no relay click no glow plugs no start.
    Glow plugs are new wiring has all been checked grounds have all been checked two brand new solenoid/controllers have been tested, tried unplugging the temperature sensor in the thermostat crossover pipe tried jump starting the two lugs on the solenoid big spark lots of power would lead you to believe the glow plugs are glowing truck still won't start.
    Checked the wires going to the controller black has ground yellow I believe it was is nothing and pink has power with the key on. Lift pump is working no water and fuel batteries brand new fully charged just all of a sudden the little weight to start late on the dash did not come on anymore the whole system is dead but yet everything checks out fine. Ready to light it on fire please help

  2. #2
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    Checked all fuses all fuses are good have power ,I unplugged the fuel heater because I was told it's on the same circuit and if it's shorted out, unplugged it no difference. The really interesting part for me is this truck has always fired right up and ran never had an issue so why now even when I jump the glow plugs it won't start.leads me to believe there's more to it than just the glow plug circuit I don't know what's going on could it be the PMD could it be the ECM could it be the ignition switch in the column I am at a loss

  3. #3
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    Latest update. I went to check exactly what the glow plug circuit malfunction obd code was and now none of my obd2 code readers will connect to the truck! Key on and wont connect ,says error unable to communicate. Never did that before. Now im leaning towards a bigger issue than just glow plugs. Seems like a bad ground or bad ecm connection somewhere. I've checked every single ground i can find and they all look good and tight so far. Anyone know how or where the ecm is grounded?

  4. #4
    Join Date
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    Welcome aboard!

    I think you touched on the most likely suspect in your #2 post. The ignition switch. It can/will cause all of the above if/when it fails. The course of your symptoms certainly points in that direction. The other suspect(s) may be the GP control circuit from the PCM (loss of contact or damaged conductor), or the relay on that circuit. The loss of OBD connection supports that, as well.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  5. #5
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    Thank you so much for your help, is there a way to test that ignition switch theory without just replacing the switch? Jump 12v to the correct wire on the column past the switch perhaps?

  6. #6
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    You can, but I'm not going to suggest you "jump" battery voltage to the PCM, in any case. That may not end well. The switch has several Batt+ outputs that power several systems. The switch isn't so expensive or difficult to replace to justify an extensive diagnostic, especially when it is a common point of failure. When it comes to the ign switch, it's best to eliminate everything else as best you can, then just replace it if that's what's indicated. If it hasn't been replaced, well, it's 20+ years old, and they often don't last that long. Even if it isn't the root problem, it's very likely due. If you can't locate a conductor, controller, or relay failure, the next step is a suspect PCM. The ign switch is the least expensive option at this time, by a long shot.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  7. #7
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    Newberg Oregon
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    I agree with Maverick 100% on the ign switch.

    Here is why.

    Example....The switch body is plastic and the contacts are copper.

    The Very cold temps cause things to shrink.

    We had temps in the upper teens a couple weeks ago....the head light switch in my Suburban would not turn the lights on....I let the rig sit with the heater on and after the cab warmed up nice a cozy....the light switch worked fine....

    If you can...put an electric heater in the cab and warm it up really well....Give it a go and see if your gremlin goes away.

    REPLACE THE SWITCH.
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

  8. #8
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    Thanks guys, I will order an ignition switch and hope thats it. Ill let you know. Cheers

  9. #9
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    Does anyone have wiring diagrams and plug pinouts for the glow plug and cpu circuits?

  10. #10
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    Ok well i finally put in the new ignition switch and unfortunately that is not the problem. $200 gamle and lost😔. Any other ideas , anyone have pinouts for ecm and glow plug circuits anywhere?

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