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Thread: Coil specs 98 3.9v8

  1. #1
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    Coil specs 98 3.9v8

    Hey guys I have a 98 disco that isn't starting.(surprise) i get no spark to the plugs so i checked the coil ,I get 3.7volts to the coil with the ingnition on and it drops to about 2.9volts with cranking ,(Is this right ?) also the restance of the coil I have is 8ohms in the Center and .2 to the out side poles (i read the Center should be 13ohms and out side .5 ) any help would be great ! Thanks

  2. #2
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    Try hotwiring the ignition (+) terminal straight to the battery or the ignition wires under the dash. You should have the same voltage at the coil as at the battery. Maybe your security system is malfunctioning.

    Try another mulitmeter too, el cheapo ones aren't very useful except for comparism with known voltages/resistances.

    But probably your ignition module is fried, a Bosch one can be substituted. Thread here:

    http://www.aulro.com/afvb/technical-...sch-024-a.html

  3. #3
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    Thanks !I was just reading That , so the restance readings of the coil are fine ? I've ordered a new one any way , ok so here's what I have ( I took the coil out to test it)
    Attached Images Attached Images

  4. #4
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    I also tried putting 12v straight to the coil , and nada

  5. #5
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    Crook coils are rare, dead modules are 50x more common. Also test the dissy pickup by disconnecting the red and blue wires from the plug near the coil. It should show some thousands of ohms and react to the rotor moving past the pickup by fluctuating the resistance reading.

  6. #6
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    Thanks for your help bee utey , I've just finished the conversion but still no luck , I now get .8 dropping to .6volts at the coil , i dont have a spider unit so not sure how to see if the alarm is busted . The battery went flat and we changed it a few weeks later and now all this! Also the truck runs LPG the system is an imco I think when I press the button on the side it hisses so gas is there ...

  7. #7
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    Just did that I get 3.5k and it goes spastic when cranked , jeepers maybe on to a car carrier and off to landrover Darwin ! Unless some one knows a better garage up darwin way!!

  8. #8
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    Start with a fully charged battery

    Make sure your multimeter has a secure negative side earth at the battery negative or the engine block. Your test leads may be broken.

    Test the voltage at the battery (+).

    Test the voltage at the white wire out of the ignition switch.

    Test the voltage at the (+) wire to the coil with it disconnected from the coil.

    Test the voltage with the same wire reconnected to the coil.

    Check you haven't accicentally earthed the negative side of the coil. A coil should have a very high resistance (ie no connection) to earth when not firing.

    Disconnect the noise suppressor to make sure it isn't shorted internally. I have seen a couple short out and melt recently, on a Toyota Camry.

    It's no good saying you've got 0.8V at the coil without checking all the rest. It's the voltage lost along the path that counts. Then you start looking for dud connections.

    Your dissy pickup sounds like its fine. 3.5K is good.

  9. #9
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    Ok I get 12 at the battery and at the key but the black + I get 2.6volts and from the white nothing when I connect them back to the coil I get the same .8 that's with the noise suppressor disconnected ....so between the ignition and the coil I'm losing 10 volts ok start looking for a broken wire ?

  10. #10
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    If there's nothing at the plain white wire its broken somewhere because that's the wire from the ignition switch. Try hotwiring it direct to the ignition white wire under the dash.

    Don't know what the black wire is for. Is it from the gas system? Most gas systems use a wire from the negative side of the coil to allow gas to flow only when there's actual spark. Maybe its connected wrong on your car and is actually allowing some voltage in from the gas switch.

    There should be a white wire with a black stripe that connects the negative side of the coil to the ECU to tell it the engine's running.

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