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Thread: 6.2L Glow Controller Issue

  1. #1
    Join Date
    Sep 2000
    Location
    California
    Posts
    98

    Default 6.2L Glow Controller Issue

    I've been running the '85-newer style glow controller on my 6.2L along with a resistor to increase the glow times (for use with the AC 60G glow plugs) and all has been great. In warmer weather when it's over 95 degrees outside or so, sometimes the glow plugs do not cycle for a warm restart and that sometimes causes harder starts. Anyone have an idea why the plugs might not be cycling in hot weather? I'm not running one of those inhibit switches that prevent the glow plugs from cycling when the coolant temp is over 125. Could it be a failing controller?
    Bob

    '83 K2500, 6.2L J-code, NV4500, NP208, 3.73 gears

  2. #2
    Join Date
    Apr 2001
    Location
    CA
    Posts
    13,568

    Default

    No, it's working as advertised. The 85+ (OEM or aftermarket clone) controller has a temp switch on-board. A heat-soaked engine compartment during summer may prevent a glow cycle. Simply, it doesn't cool down fast enough. It's easy enough to just bypass it with a cheap Ford starter relay and momentary switch.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  3. #3
    Join Date
    Sep 2000
    Location
    California
    Posts
    98

    Default

    Oh, gotcha. I know some 6.2Ls don't need the glow plugs to start when it's warm/hot, but some do, and, unfortunately, mine is one of those. Maybe I'll look into the momentary button. I had thought going to the '85-newer setup would be the final glow plug modification I'd need to do.

    Thank you for the information. Appreciate it.
    Bob

    '83 K2500, 6.2L J-code, NV4500, NP208, 3.73 gears

  4. #4
    Join Date
    Aug 2019
    Location
    Joliet, Illinois
    Posts
    29

    Default

    Echoing the previous reply, the controller bypass is wonderful and easy to get wired up. In my opinion it's better than any controller because it puts you in complete control of when and how much glow you use in any given situation.
    1983 Chevrolet C20

    1923ish Ford Model T Touring

    2000 Lincoln Town Car

  5. #5
    Join Date
    Aug 2021
    Location
    Los Angeles, CA
    Posts
    26

    Default

    I had the same problem as BobQ where the glow plugs would not cycle at certain times leading to hard starts. Although I didn't know it at the time, as DMax mentioned, there is a temperature inhibit switch within the glow plug controller that cannot be bypassed. After bypassing the coolant-based temperature switch that is upstream from the glow plug controller (which didn't fix the problem) and replacing the glow plug controller itself (which didn't fix the problem), I was able to figure out that the glow plug controller itself had a temperature inhibit switch within it, which cannot be bypassed. I ended up wiring in a relay and momentary switch so that I could control the glow plug circuit manually. It works great, though I do worry that my wife, or the tire guy, etc will run the glow plugs for too long causing the tips of the glow plugs to swell, which I understand is somewhat common in the 6.2 and can be a pain to deal with. Here's the kicker: During the repair process, I found out that the root cause of my hard start problem was actually a weak set of batteries. The weak batteries were not turning the starter at a fast enough speed to generate the heat that would be required for a normal start during the times that the engine was only slightly warm (just warm enough to open the temperature inhibit switch within the glow plug controller.) If I had to do it over again, I would probably keep the original setup, which had worked fine for the 10 years that I have driven it. With the original setup, you have the security of knowing that if it ever doesn't function correctly, you can always jump the glow plug relay and activate the glow plug circuit manually. Then you don't have to worry as much about getting into an argument with your wife.
    1992 Chevy G20, 6.2 NA

  6. #6
    Join Date
    Feb 2000
    Location
    Montana
    Posts
    11,375

    Default

    Normally, the 6.2/6.5 doesn't need glow to start if the engine temperature is above about 80 degrees F.

    Those that do have some sort of problem. Injection timing, worn fuel injection pump/injectors that produce improperly atomized fuel, low cranking speed, thin fuel (i.e. #1 diesel in warmer temps), low cylinder compression, low cetane fuel, and so on... These are the most likely.

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