no spark - coil

[70sixpack]

Trying to figure out why I have no spark form my coil. It is a v code car and all worked 2 years ago before the restoration. Now I have juice to the coil, but it only 6.95 volts and no spark at all from the coil to the distributor. The electronic control unit # 4120505 is brand new. Any ideas? I did ohm test the coil and it was within range.. Just trying to resolve this si I can fire her up and take it for a ride, it's been a long 2 years....

Just checked the voltage again at the coil, when I disconnect the negative wire it read 11.96 volts

 

[70rr-brian]

Points or electronic ignition?

 

[70sixpack]

Points or electronic ignition?

electronic ignition.

 

[70rr-brian]

I guess I should have got that from the ECU. LOL That's what happens when you only half read. Why did you replace the ecu? Just curious more than anything. Was it the same type of ECU or different one? 2 or 4 pin ballast?

 

[kiwigtx]

Recent restoration suggests a build or film of paint between the ECU and the grounding to the body of the firewall. Check continuity (zero ohms) between body of ECU and the bolt that secures it + between body of ECU and battery negative when connected. That will give the ECU its ability to run, then if that doesn't work, we can explore more.

 

[70sixpack]

Recent restoration suggests a build or film of paint between the ECU and the grounding to the body of the firewall. Check continuity (zero ohms) between body of ECU and the bolt that secures it + between body of ECU and battery negative when connected. That will give the ECU its ability to run, then if that doesn't work, we can explore more.

ballast 2 prong.

ok when I have the key on and my ohm meter set at 20k, negative lead to negative battery cable positive to bolt holding ECU I get around 1 ohm..

 

[kiwigtx]

Have you checked the magnetic pickup gap - should be around 0.008" - 0.010", and I assume the rotor is installed/clean and cap is good?

 

[coloradodave]

Try it again with your ohmeter set to 20 ohms, not 20,000 (k).

 

[kiwigtx]

Try it again with your ohmeter set to 20 ohms, not 20,000 (k).

Well spotted Dave...should have seen that myself ;)

 

[kiwigtx]

ballast 2 prong.

ok when I have the key on and my ohm meter set at 20k, negative lead to negative battery cable positive to bolt holding ECU I get around 1 ohm..

Are you actually getting 1 ohm? or is the meter reading 1?
With my meter, if I get the result of 1, it means an open circuit - which in your case means no continuity.
Please check again on the lowest scale possible and get another reading for us.

 

[70sixpack]

Are you actually getting 1 ohm? or is the meter reading 1?
With my meter, if I get the result of 1, it means an open circuit - which in your case means no continuity.
Please check again on the lowest scale possible and get another reading for us.

OK. With the meter set at the lowest setting (200) i get 5.1 on one screw and around 11 on the other?? Not sure what this tells me..

 

[70sixpack]

Ok. I have 12 volts on both sides of the ballast resistor. I also have 11.49 volts to one side of the coil. But I still have no spark out of the coil..

 

[HT413]

Sorry this not exactly your situation, but my MSD 6AL instructions say the only way to be certain it isnt a bad coil is to retest with a known good coil. Heck, a coil cost like $30 at the local autoparts store, maybe worth taking a drive. You can always return it if it proves the coil is not the problem.

 

[70sixpack]

Sorry this not exactly your situation, but my MSD 6AL instructions say the only way to be certain it isnt a bad coil is to retest with a known good coil. Heck, a coil cost like $30 at the local autoparts store, maybe worth taking a drive. You can always return it if it proves the coil is not the problem.

I already did that

 

[HT413]

Do you have 12v to the coil with the ignition in 'start'? Could be the run leg on the ignition is good but the start leg has the problem.

- - - Updated - - -

Remember that in the 'run' position, the dark blue (tracer) is hot. In start, the yellow is hot to the starter relay and the brown is hot to bypass the ballast resistor and give spark while starting. After the car is started and you put the ignition switch to run position, the brown is no longer hot and it is now the dk blue tracer that provides voltage to the ignition... through the ballast reseistor. have a helper put the ignition to start while you test w voltmeter. (disconnect the yellow from the starter relay to prevent the car from turning over).

 

[67 coronet]

Ok. I have 12 volts on both sides of the ballast resistor. I also have 11.49 volts to one side of the coil. But I still have no spark out of the coil..

why do you have 12 volts to BOTH sides of the ballast resitor?its supposed to drop voltage.this could indicate a problem.

 

[70sixpack]

why do you have 12 volts to BOTH sides of the ballast resitor?its supposed to drop voltage.this could indicate a problem.

One side is a little over 12 and the other side is a little under 12

- - - Updated - - -

Do you have 12v to the coil with the ignition in 'start'? Could be the run leg on the ignition is good but the start leg has the problem.

- - - Updated - - -

Remember that in the 'run' position, the dark blue (tracer) is hot. In start, the yellow is hot to the starter relay and the brown is hot to bypass the ballast resistor and give spark while starting. After the car is started and you put the ignition switch to run position, the brown is no longer hot and it is now the dk blue tracer that provides voltage to the ignition... through the ballast reseistor. have a helper put the ignition to start while you test w voltmeter. (disconnect the yellow from the starter relay to prevent the car from turning over).

I only checked it in the run position. I'll do it in the start position and let you know.
Thanks!!

 

[67 coronet]

should be a bit above 12 in and about 9 volts out.may indicate a wiring issue.what is the voltage of your battery?needs to be above 12.6 to test electrical.

 

[70sixpack]

Do you have 12v to the coil with the ignition in 'start'? Could be the run leg on the ignition is good but the start leg has the problem.

- - - Updated - - -

Remember that in the 'run' position, the dark blue (tracer) is hot. In start, the yellow is hot to the starter relay and the brown is hot to bypass the ballast resistor and give spark while starting. After the car is started and you put the ignition switch to run position, the brown is no longer hot and it is now the dk blue tracer that provides voltage to the ignition... through the ballast reseistor. have a helper put the ignition to start while you test w voltmeter. (disconnect the yellow from the starter relay to prevent the car from turning over).

Here's what I got. Test light only lights up on the one the ballast side of the coil. When I had tested the voltage with the key in the run position (turning over) I had 9.8 on the ballast side and 9.7 on the dist. side..

 

[moparbud66]

Check my thread from last year "Spark seems weak". I got alot of very informative responses. Good Luck.