Author Topic: No Spark???  (Read 4912 times)

Offline mjb765

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No Spark???
« on: April 20, 2011 - 05:48:00 PM »
It's a 71 340 Challenger...factory electronic ignition....ran perfect yesterday...went out this morning and cranks but won't start--no spark at the coil. Tried a new coil--still no good. Power at both sides of the resistor. I'm thinking ignition module--does this sound right???




Offline 72rtchallenger

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Re: No Spark???
« Reply #1 on: April 20, 2011 - 06:03:22 PM »
could be ignition module or ballast but you might want to check your bulk head plug connections and grounds
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Offline MEK-Dangerfield

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Re: No Spark???
« Reply #2 on: April 20, 2011 - 07:14:14 PM »
I agree with the above, but when you say power on each side of the ballast resistor, what voltage are we talking about?

Mike

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Offline dodj

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Re: No Spark???
« Reply #3 on: April 20, 2011 - 08:37:21 PM »
12vdc (or there-abouts) on the brown wire at the resistor when you have the key turned to start?  :popcorn:
Scott
1973 Challenger  440 4 spd 
2007.5 3500 6.7 Cummins Diesel, Anarchy tuned.
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Offline mjb765

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Re: No Spark???
« Reply #4 on: April 20, 2011 - 10:33:41 PM »
12vdc (or there-abouts) on the brown wire at the resistor when you have the key turned to start?  :popcorn:

While cranking ...I didn't check..I will look at that tomorrow.

Didn't measure exact voltage, just checked for power with the test light.

Offline mjb765

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Re: No Spark???
« Reply #5 on: April 23, 2011 - 03:23:51 PM »
Good power on both sides of the resistor even while cranking. What I did notice is that I have power on both sides of the coil--all the time.....doesn't that side pulse to fire the coil?

Offline dodj

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Re: No Spark???
« Reply #6 on: April 23, 2011 - 09:05:39 PM »
I've never tried it but the -ve wire that is controlled by the ECU would switch very quickly so I don't know if you would see it with a digital meter, possibly with an analog (needle) type.
You say you have 12vdc on the brown while cranking, so the ign switch is not the problem
Even with a bad ballast resistor it would fire at least until you released the key - then it would die. So I would cross out the ballast resistor and switch out the ECU.
Scott
1973 Challenger  440 4 spd 
2007.5 3500 6.7 Cummins Diesel, Anarchy tuned.
Good friends don't let friends do stupid things. ........alone.

Offline mjb765

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Re: No Spark???
« Reply #7 on: April 23, 2011 - 10:05:37 PM »
I've never tried it but the -ve wire that is controlled by the ECU would switch very quickly so I don't know if you would see it with a digital meter, possibly with an analog (needle) type.
You say you have 12vdc on the brown while cranking, so the ign switch is not the problem
Even with a bad ballast resistor it would fire at least until you released the key - then it would die. So I would cross out the ballast resistor and switch out the ECU.

I eliminated the key and resistor by putting 12V directly to the + side of the coil and cranking it at the solenoid. Still no spark.....then I tried a new ECU and still no spark......The only think I can think of is the distributor pickup.

Offline dodj

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Re: No Spark???
« Reply #8 on: April 24, 2011 - 07:37:35 AM »
The only think I can think of is the distributor pickup.
Aside from a wiring issue between coil -ve and the ECU and the grounding of the ECU, I think that is all that is left. You probably already know but I'll mention it anyway, -  0.008 reluctor gap, remember to use a non-magnetic gauge.  :cheers: :popcorn:
Scott
1973 Challenger  440 4 spd 
2007.5 3500 6.7 Cummins Diesel, Anarchy tuned.
Good friends don't let friends do stupid things. ........alone.

Offline mjb765

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Re: No Spark???
« Reply #9 on: April 27, 2011 - 07:57:23 PM »
Distributor pickup arrived today...installed and started right up! May buy a distributor---it seems the gap at the pickup is not even--closer at the bottom than the top and everything is installed and seated correctly. Strange..but it runs fine....

Offline Chryco Psycho

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Re: No Spark???
« Reply #10 on: April 28, 2011 - 12:37:54 AM »
I usually have to bend the pick up Bracket to get it aligned right   

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Offline mjb765

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Re: No Spark???
« Reply #11 on: April 28, 2011 - 05:43:53 PM »
I usually have to bend the pick up Bracket to get it aligned right

I guess I will get out there this weekend and start bending....