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Used an Ohmeter to check coil, need help with the results

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Waxer, May 8, 2000.

  1. Waxer

    Waxer 1/2 ton status Author

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    I am having acceleration problems and I suspect it is something electrical. I have previously replaced everything, except the coil. I suspect it is bad, but I dont have alot of cash, but do have a mulitmeter to check it. The haynes manual says to first connect the tach/batt terminals and the needle should go over to zero ohms, which it did. Then it says to connect the tach terminal and the center terminal on the cap, then connect the ground terminal to the center terminal on the cap, if they both read infinite resistance, replace the coil, the book says. My question is what the hell is infinite resistance?? When I did connect those last 2 times, the needle didnt go over to zero, it stayed at 2k ohms, actually the needle didnt move at all. Does that mean its reading infinite resistance? If so, I have a bad coil, dont I???
    ok, update: I turned the dial to the high reading, and the last test gave me 11k ohms, when the other was still infinite
     
  2. 6.2 man

    6.2 man 1/2 ton status Premium Member

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    What it means is if the numbers come up all 000's or the needle pegs out you've reached infinite reading . If you have any more questions let me know .
     
  3. Michael

    Michael 1/2 ton status

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    If you read zero; that is a short, just like a piece of wire. Infinite is unmeasureably high resistance......maximum. Maybe Eagle could explain this one better.....Ray? Sounds to me like you may be OK.

    Michael [​IMG] http://jmartin.net/parker/goose.htm
     
  4. Thumper

    Thumper 1/2 ton status

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    If it wants you to read infinite resistance, the numbers cant read 000. Infinite means no continuity at all, the way the meter reads when the leads arent connected to anything. A reading of 000 would indicate a short. BTW, what kind of probs are you having? I had some ignition probs, and by doing those tests in the manual I replaced the whole dang system before I figured out that it was the pickup coil. It had a broken wire , but it would only break connection when the unit would advance. At idle it worked fine, but when I accellerated it would cut out and Id lose ignition, until the advance retarded back to normal then it would make contact again... Needless to say a very frustrating expensive weekend!
    Every test I did out of the Haynes book came up no good. I replaced the coil, the module, and the pickup coil before it was fixed.

    Mike


    <font color=blue>Thumper
    85 Fullsize Jimmy
    [​IMG]
    <font color=red>Lets Go Wheelin! </font color=red>
     
  5. Eagle86K5

    Eagle86K5 1/2 ton status

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    Basically, what you have is called a step-up transformer, in that, it takes 12vdc(volts direct current) and changes it to upwards of 50,000 vdc. You have two coils of wire wrapped around an iron or steel core. In the attached photo, you will see the windings, the primary being labled "A" and "B", the secondary labled "C" and "D". The primary windings would be the Battery and the ground, while the secondary winding would be the to the distrubitor and ground.
    To test, depending on which type of meter you are using, there is the digital which has usually three zero,s in the screen when you start, and an analog which has the arm that moves back and forth, whichever one, turn the meter to the lowest resistance scale, then place both leads together and watch what happens, the analog will "peg" the scale, in that it will go to full scale deflection, this is usually a good time to set the zero scale adjustment. On my digital when the leads are connected together the screen will show a small resistance, the resistance of the leads, usually .003 ohms, this is showing continuity.
    Now to test the coil, place the leads on A and B or Battery and ground, you should get full scale deflection on the analog and a small resistence on the digital,continuity, do the same with the center electrode and the case of the coil C and D, you should see the same thing. If on either side you get no reading at all then there is an open in the coil and it would not work at all. To test for a short in the coil place your lead on A and C, the analog meter should not move any at all and the digital will remain "000" or infinite resistance in that it can't read anything. If you get any readings at all here that means that there is an internal short to the coil, and it is bad.
    Personally I would opt for the digital meter because it will allow you to see more accurate and minute readings then the analog.
    Hope this helps...and thank Micheal for the plug...check is in the mail...heheheheh

    <font color=green>[​IMG]Eagle86K5[​IMG]<font color=red>
    Masonry...It's a Good Thing
    2B1ASK1
     
  6. Eagle86K5

    Eagle86K5 1/2 ton status

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    Darn fergot the attachment, anyone seen my head...

    <font color=green>[​IMG]Eagle86K5[​IMG]<font color=red>
    Masonry...It's a Good Thing
    2B1ASK1
     
  7. Michael

    Michael 1/2 ton status

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  8. bart

    bart Registered Member

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    waxer-
    you say acceleration problems...replaced everything electrical..including the little pickup coil in the bottom of the distributor...GM HEI, I assume...

    if you did everything electrical...did you look at the vacuum advance setup at all? This would surely cause acceleration problems.

    Just another shot in the dark...

    Bob
     
  9. Waxer

    Waxer 1/2 ton status Author

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    Well, the whole dist is brand new from Jegs. It is an HEI. All my acceleration problems started after I went through this deep mud/water hole. I replaced the coil today, only to find that the problem is still here. I did somewhat clean the carb out, which had all kinds of crap inside of it. The carb is 2 weeks old BTW. Edelbrock Performer 600cfm. I wasnt able to clean out the jets and passageways, but I did spray out the bowl, and venturies. I guess I still have some crud in the carb I need to get to. I'll keep everyone informed on my progress tomorrow. Thanks for all the helpful responses.
     

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