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  1. #1

    Join Date
    Jan 2002
    Posts
    154
    Location
    Baton Rouge, LA
    Tractor
    Kubota ZD21

    Default Glow Plug question

    Hello All. I just bought an old toyota diesel pick, and the glow plugs are not working. Well, I can replace them easy enough. One thing I find myself asking is, how do you know when one goes out? It's pretty obvious when 3 or 4 go out, (on a 4cyl)
    but how do you tell if you lose 1 or 2?
    I guess you could measure total current, but I don't have anything that measures 80 amps!

    Thanks

  2. #2
    Silver Member
    Join Date
    Aug 2000
    Posts
    209
    Location
    Louisa, Virginia
    Tractor
    John Deere 790

    Default Re: Glow Plug question

    Here's how I check the glow plugs on my F350 - I have a wire with alligator clips on both ends, attach one to the positive terminal of the battery and they touch the other end to the glow plug, if I get a spark I know the plug is working somewhat, if not spark, then I know its open and should be replaced. On the Ford, the glow plug controller depends upon the resistance in the glow plugs to function correctly. If a glow plug goes, you notice the controller cycling faster then if all are working. Don't know about the Toyota. Hope this helps.

  3. #3

    Join Date
    Jan 2002
    Posts
    154
    Location
    Baton Rouge, LA
    Tractor
    Kubota ZD21

    Default Re: Glow Plug question

    There is a controller, and some sort of resistance measurement happening. The glow plugs have power for about 90-120 seconds after the key is first turned on. I have ordered the OEM service manual, and will learn more when I get it, but I'd like to attack the glow plug issue promptly.

    Will it hurt the engine spinning over without the glow plugs on?

  4. #4
    Super Member
    Join Date
    Dec 2000
    Posts
    6,737
    Tractor
    JD 8320 MFWD, JD 6415 MFWD, FEL, and cab, John Deere MFWD 4600, John Deere 4020, John Deere 4430, John Deere 455 mower, Deutz, and Gehl 4610 perkins skidsteer

    Default Re: Glow Plug question

    Ben,
    You can check them just like Halsey said. Also it won't hurt to turn it over without the glow plugs on.

  5. #5

    Join Date
    Jan 2002
    Posts
    154
    Location
    Baton Rouge, LA
    Tractor
    Kubota ZD21

    Default Re: Glow Plug question

    Is there a way to tell if you have one out while it's still in the engine?
    What's the first indication that one is out?

  6. #6

    Default Re: Glow Plug question

    <font color=blue>...Is there a way to tell if you have one out while it's still in the engine?...</font color=blue>

    Simply disconnect the B+ lead going to each individual glow plug terminal and ohm it out from that terminal to ground. {Warning... Not all glow plugs operate on 12volts... some operate much less (the controller pulses the B+)... so it's not advisable to "just hook up 12 volts and test for smoke...?"}

    A good glow plug will read ~~1-3 ohms {or a very low resistance}. A bad glow plug will read open or infinity. A glow plug is nothing more than a "miniature heating element" with a controlled "on" time.

    While the B+ wire is off you can check for voltage at that plug with the switch on.

    Hard starting is one indication a glow plug or a few are out...


  7. #7
    Veteran Member
    Join Date
    Sep 2000
    Posts
    1,370

    Default Re: Glow Plug question

    Ben,

    If you have a voltmeter capable of measuring millivolts, you can measure the drop in the wire to the plug when the glow plug is on. At ~10-15 amps/plug you should be able to see a few 10's of millivolts for a plug that is operative, zero if it's not.

    Al

  8. #8

    Join Date
    Jan 2002
    Posts
    154
    Location
    Baton Rouge, LA
    Tractor
    Kubota ZD21

    Default Re: Glow Plug question

    Thanks everyone. So, is it common practice to periodically pull your plugs, and chaeck them, or just when it gets hard to start?

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