No Spark???

[mjb765]

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???

[72rtchallenger]

could be ignition module or ballast but you might want to check your bulk head plug connections and grounds

[MEK-Dangerfield]

I agree with the above, but when you say power on each side of the ballast resistor, what voltage are we talking about?

[dodj]

12vdc (or there-abouts) on the brown wire at the resistor when you have the key turned to start? 

[mjb765]

12vdc (or there-abouts) on the brown wire at the resistor when you have the key turned to start? 

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.

[mjb765]

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?

[dodj]

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.

[mjb765]

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.

[dodj]

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. 

[mjb765]

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....

[Chryco Psycho]

I usually have to bend the pick up Bracket to get it aligned right   

[mjb765]

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....