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I have a 97 Dakota 3.9 that has no spark from the coil. I tested with a spark tester then checked the coil harness connecter for 12.5 volts.I get battery voltage at the connecter for 1 second after the key comes on then the voltage drops to zero.I tested the resistance for the coil and it tested with in spec. Any help is appreciated. Thanks!!
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Is there a check engine light on?
Also out of curiosity, did you test the primary and secondary windings of the coil?
You could use a test light on the negative side of the coil to see if it flashes when you try to start the vehicle. If it does flash then the problem is not with the triggering device (that being the pickup coil in the distributor as well as the crank sensor also). You would need to look at the distributor cap, rotor, wires and so forth.
If the test light does not flash, then there is an issue with one of your triggering devices most likely being the pickup inside the distributor. So you would need to trace from the positive side of the coil back.
A wiring diagram would be helpful here.
All this is on the assumption that you have fuel going to the fuel and there are no codes for your crankshaft position sensor. If there was an issue with that area, would would get no ignition spark or injector pulse.
Hope this helps.
Thanks for the replies!!! The primary resistance is of the coil is 01.7 ohms,Secondary is 13.53. There is 1 coil that fires all the plugs. No check engine light. Is it normal to only to have battery voltage at the coil harness connecter for 1 second?
dreamer,
I think i got this test right. With a test light connected to body ground, the probe to the negative wire on coil harness connecter with it plugged in the coil and have someone crank the engine,look for the light to flash?I will test tomorrow .I’ll let you guys know.Thanks!
Hi mobcittty,
What were your resistance readings for the primary and secondary? Does the coil service all the spark plugs, or is there an individual coil for each spark plug? Keep us posted.Thanks mobcittty for the measurements. Just wanted to double check the units. For the Primary coil, the measurement is 1.7 ohms. For the Secondary coil, is the measurement 13.53 ohms, or 13.53 k-ohms (kilo-ohms)? Keep us posted.
The negative side of the coil is a ground so you will have to put the flash light on B+. Try it both ways and you will see. That’s how we learn half the time C8-).
I would recommend getting into the habit of using a DVOM though for voltage checks as there more accurate and more safer when dealing with circuits that use less than battery voltage such as 5vREF circuits and so forth as a test light pulls 12v.
I wouldn’t bother checking the coil resistance on a coil as I’ve never found that to be an accurate test, I’ve also confirmed that with electrical engineers. That said what you want to check for is the primary signal at the negative coil terminal as you crank the engine. Try putting a test light through the back of the connector on the negative side as you crank and hook the other part of the tester to battery negative, as you crank the engine look for the light to flash if it does and you still don’t have spark then the coil is the issue, if it doesn’t flash then the issue is in the primary side of the ignition system which could mean a bad module. You also want to confirm that you have power to the positive side of the coil, if you don’t have power here then check the fuses and the wiring. Good luck.
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