NO spark question

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Mophile

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So in my 68 340 dart I had an electrical failure, car just shut off. I've changed ignition switch,voltage reg, ecu, and coil swapped with a working one. I know new doesn't always mean good but... I'm getting 12.5 v at the battery with the y off and 12.5 at the starter relay with the key off. when i turn the key i get 12.1 at the starter relay, 11.6 at the voltage reg, and11.2 at the coil. I had someone crank it over and voltage dropped to 8.9 at the coil. but no spark coming out of the coil?? Any thoughts??

thanks
 
I went recently went through this with my 69 Charger. I changed the ballast resistor (typical mopar problem) still no spark. I assumed the old coil might have been shot so replaced that...still no spark. Well only thing left was the ignition box, boom fired right off even on 7 cylinders (had one plug out looking for spark). Now I wish I could have checked the voltages but I had a new box in stock, coil I knew I could take back to autozone it it wasn't the problem, and everyone should have a ballast resistor in the glove box.
 
A...PLEASE do yourself a favor and stop replacing stuff until you have a game plan on "whut's wrong."

B...AFTER you try "1" and can't find a solution, sometimes throwing parts at it is what's left

So..................Let's troubleshoot the ignition

Get it "right down" to the "simple."

COIL+ voltage SHOULD be different depending on whether the points are open or closed. I assume? you have breaker points and not electronic?

Clip meter to coil, turn key to "run." If points happen to be open, voltage will be "same as battery"

"Bump" engine until points close. Voltage should go quite low, perhaps 8V or so. Now check voltage at the "key" side of the ballast resistor, which should STILL be "same as battery."

With key still in "run" and points closed measure points voltage that is coil NEGATIVE. This should be quite low. The higher that voltage is, the worse the points are, IE they have high resistance.

Now, bear in mind that when you CRANK the engine USING THE KEY this is supposed to bypass the coil resistor by means of the ignition switch. This is the brown wire on "one end" of the ballast resistor, and is called "IGN2"

So with your meter on coil+ crank the engine USING THE KEY and read voltage while cranking. Should be very close to "same as battery" and in no case less than 10V

Are the points closing and opening?

Is the condenser (inside the distributor) good? Try another one

Is the coil good? Save it for 'last." Determine if the points are opening / closing and test for spark. If the points are able to switch (draw current) and no spark, then change the coil.

CHECK THE SPARK using a grounded probe or an "inline" spark tester. They are cheap at the parts store

1...."Rig" the test gap right at the coil tower. Do NOT use the coil wire. It might be bad. Crank the engine USING THE KEY and watch for spark.
2....f the coil+ cranking voltage was low in the tests above, then "rig" a clip (alligator) lead from coil + to the big battery stud on the starter relay and try again, testing for spark. Maybe the IGN2 contacts are not working Spark should be nice, blue, snappy, at least 3/8" long

3....If you get good spark above, could be a bad coil wire. Check it for resistance. The 'old school" resistance standard for radio suppressed wires is less than 1000 ohms per foot.

4....If the coil wire seems good, look inside the cap and rotor. Look the rotor over carefully for damage, "punch through," and look them both over for moisture, grease, "carbon tracking," etc

5...While you are in there, look around generally. Wiggle the dist. shaft and check for wear and side play

ALSO download yourself a factory shop manual if you don't have one. MyMopar has them free

http://www.mymopar.com/index.php?pid=31
 
The 8.9 V at coil was measured from coil+ to where? If BATT-, try putting the black lead on the engine block, or better the distributor case if you have points. You could be getting a voltage drop on the return to the battery, especially while cranking.

To test the coil and its power source, don't crank the engine. Disconnect coil- and connect a jumper. Quickly ground coil- w/ the jumper and release (ground to block). Each time you release, you should get a spark. If not, try grounding to BATT-. If that works, then you don't have a good return from block to BATT-. If doesn't work, and coil+ is still >8 V, the coil is probably bad. The spark should be right off the coil tower to the block (1/4" gap), taking the distributor out of the equation. If that sparks, start putting things back to factory and see when the spark fails. Sometimes it is sparking, but along the surface of the distributor cap where you can't see it (carbon tracking).
 
carbon tracking is an interesting idea. I'm gonna try your test and 67 dart 273's test in the AM. keep you posted
 
One more for the back of your mind.

Coil wires can burn their core down through the center of the wire so far the spark won't jump that gap any longer.
You should see a short section of the core bent over and crimped under the metal end.
If you see nothing but a black hole down the center of the wire, then the core is probably burned away. (mostly a reference to coil wires, but it can happen to plug wires also)
 
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