Power to the coil but no spark.

[19Dart74]

Hello all,
I'm so close to bringing my Dart to life. I have crank and fuel but no spark. I bought a spark plug test light and verified. I looked for voltage to the coil with key on and it is getting a bit over 6 volts on the positive and 1.5 volts on the neg. I checked the connector going to the distributor and it was the same 1.5 volts. Turning the key brings the positive side of the coil to a bit over 11 volts. I replaced my spark pugs and checked all the connections. My ignition module is also grounded. I'm at a loss.

 

[Syleng1]

Remove the negative side coil wire and with the key on tap it to the stud. The break should cause a spark. Every time to touch it to ground terminal (black with yellow tracer) it should cause a spark to the coil wire.

 

[67Dart273]

Remove the negative side coil wire and with the key on tap it to the stud. The break should cause a spark. Every time to touch it to ground terminal (black with yellow tracer) it should cause a spark to the coil wire.

There's a better way which will check the module. Simply pull apart the distributor 2 terminal connector, and take the connector end in the engine bay, not the distributor end. With the key in "run" and a test spark gap rigged to the coil tower, repeatedly tap the bare terminal of that connector to ground. Each time, you should get a nice hot "snap" spark.

OP Your voltage test does indicate one good thing. With the key in run, and getting around 6V this shows you are getting power, that the power is going through the ballast, and that the coil is grounded through the module and drawing current.

Try working the distributor connector in/ out several times to "scrub" the terminals. Those connectors have almost zero current through them, and are subject to corrosion.

Inspect the interior of the distributor reluctor/ pickup area for rust, damage/ debri. Wiggle the shaft to check for side play.

Be sure to test for spark AT THE coil tower with a solid wire and test gap. If you get none by using the KEY to turn to "start" then try jumpering 12V direct to the coil + and try the test again

If the "tap tap" test of the pickup connector gives you spark, concentrate on a bad connection in that connector, a bad pickup or damage or misadjustment of the reluctor gap, which should be .008 using a brass feeler (nonmagnetic)

 

[19Dart74]

There's a better way which will check the module. Simply pull apart the distributor 2 terminal connector, and take the connector end in the engine bay, not the distributor end. With the key in "run" and a test spark gap rigged to the coil tower, repeatedly tap the bare terminal of that connector to ground. Each time, you should get a nice hot "snap" spark.

OP Your voltage test does indicate one good thing. With the key in run, and getting around 6V this shows you are getting power, that the power is going through the ballast, and that the coil is grounded through the module and drawing current.

Try working the distributor connector in/ out several times to "scrub" the terminals. Those connectors have almost zero current through them, and are subject to corrosion.

Inspect the interior of the distributor reluctor/ pickup area for rust, damage/ debri. Wiggle the shaft to check for side play.

Be sure to test for spark AT THE coil tower with a solid wire and test gap. If you get none by using the KEY to turn to "start" then try jumpering 12V direct to the coil + and try the test again

If the "tap tap" test of the pickup connector gives you spark, concentrate on a bad connection in that connector, a bad pickup or damage or misadjustment of the reluctor gap, which should be .008 using a brass feeler (nonmagnetic)

I guess I'm having a hard time following what your saying about testing the coil.... can you describe it a different way?

 

[67Dart273]

I guess I'm having a hard time following what your saying about testing the coil.... can you describe it a different way?

I don't know how. You have a Mopar OEM style ignition box, right? The coil wiring is actually the same as points. It comes from the key, through the ballast, to the coil +. The neg side of the coil is connected back to the box which switches it off when triggered, to make a spark.

When you have the key in "run", engine stopped, the coil should draw current, and based on your voltage tests, it is. This is good because it means the coil has continuity in the primary, it is getting power from the ballast, and the box is grounded, and is grounding the coil negative. So far, "normal."

The distributor 2 wire connector comes from the magnetic pickup in the dist, which triggers the box to fire the coil.

So to test everything except the distributor

1....Rig a test gap to the coil tower. Use a wire core wire, not a resistive coil wire. This is to eliminate the dist and wires, and give you a good indication of what the ignition and coil is doing.

2...Switch the key to "run."

3...Disconnect the black rubber 2 wire connector coming from the distributor. This is the ;trigger wire. Take the connector end which goes to the engine harness, and NOT the distributor. That connector will have 1 male bare exposed terminal, and an insulated, protected, female terminal. Take the connector and tap the bare terminal on a good ground, such as the side of the dist or the carb. This will trigger the box and the coil. Each time you do this you should get one blue hot spark out of the coil

 

[19Dart74]

I don't know how. You have a Mopar OEM style ignition box, right? The coil wiring is actually the same as points. It comes from the key, through the ballast, to the coil +. The neg side of the coil is connected back to the box which switches it off when triggered, to make a spark.

When you have the key in "run", engine stopped, the coil should draw current, and based on your voltage tests, it is. This is good because it means the coil has continuity in the primary, it is getting power from the ballast, and the box is grounded, and is grounding the coil negative. So far, "normal."

The distributor 2 wire connector comes from the magnetic pickup in the dist, which triggers the box to fire the coil.

So to test everything except the distributor

1....Rig a test gap to the coil tower. Use a wire core wire, not a resistive coil wire. This is to eliminate the dist and wires, and give you a good indication of what the ignition and coil is doing.

2...Switch the key to "run."

3...Disconnect the black rubber 2 wire connector coming from the distributor. This is the ;trigger wire. Take the connector end which goes to the engine harness, and NOT the distributor. That connector will have 1 male bare exposed terminal, and an insulated, protected, female terminal. Take the connector and tap the bare terminal on a good ground, such as the side of the dist or the carb. This will trigger the box and the coil. Each time you do this you should get one blue hot spark out of the coil

This for some reason makes more sense to me. Thank you for taking the time to explain it to me. I will let you know if I have spark.

 

[19Dart74]

So I did all that and did not get an arch from the coil tower. Does this mean that my coil is bad or maybe the ignition module? Can a coil be bad even though it is pulling current?

 

[19Dart74]

So I did all that and did not get an arch from the coil tower. Does this mean that my coil is bad or maybe the ignition module? Can a coil be bad even though it is pulling current?

Or maybe I have this wired incorrectly... I have to brown wire on the positive coming from the resistor. The negative has the coil condenser and the yellow and black coming from the ignition module. The one that I felt weird about is the black and Grey. From the diagrams it appeared to me that the wire is spliced, 1 from the fuse box and the other from the ignition module, between the coil and the distributor. I felt this was weird from the beginning. Maybe this is wrong.

 

[cudamark]

Has your car got an aftermarket tach of some sort? I'd start by removing the capacitor and any added wiring. Start with stock stuff only.

 

[67Dart273]

If you have a tach connected, try the test again. The one picture appears to have two wires connected to coil NEG. The tach could be bad or tach wire shorted.

If you still do not get spark, could be coil or module. Next try disconnecting the coil NEG wires completely, then jumpering the coil NEG to ground repeatedly and look for spark.

If you do get spark it is likely a bad module

 

[19Dart74]

There is no tach involved. The wires going to the neg terminal are the black and yellow from the module and the back and Grey coming from the fuse box and the module. I had though the condenser was a requirement. Is this untrue?

 

[cudamark]

That's a noise suppressor. Not needed unless you're getting static on radio.

 

[19Dart74]

If you have a tach connected, try the test again. The one picture appears to have two wires connected to coil NEG. The tach could be bad or tach wire shorted.

If you still do not get spark, could be coil or module. Next try disconnecting the coil NEG wires completely, then jumpering the coil NEG to ground repeatedly and look for spark.

If you do get spark it is likely a bad module

So I did this test and I got spark when grounding the neg terminal on the coil. Just to clarify, does this mean bad module?

 

[cudamark]

We're assuming that the distributor is turning while your cranking the engine over....right? I like to test by getting the reluctor lined up with the pickup and then just rotate the rotor back and forth to generate the spark.....keeping the coil wire attached to the coil and the distributor end a 1/4 inch or so from a good ground. This gives me a bit more info regarding the pickup and distributor as well as the other components.

 

[Mattax]

Has your car got an aftermarket tach of some sort? I'd start by removing the capacitor and any added wiring. Start with stock stuff only.

he has an aftermarket build it yourself harness kit.

Blowing Maxi Fuse immediately...?

I am totally green around the ears and strictly trying to wire my 74 Dart with the Painless harness manual and OEM wiring diagrams. I believe that I have done everything to the book. I am jumpy about posting stuff due to trying to not look like an idiot... but here goes. I have wired the entire...

www.forabodiesonly.com

I don't know why there are 3 wires connected to the coil negative.

Ignoring the capacitor, there should be one wire from the Ignition 2 (start) side of the ballast resistor to the positive on the coil.
On a '74 that would have originally been Brown and 16 gage IIRC.

There should be one wire connecting the coil negative to the ECU.
(The wire to the top of pentagon connector is power in. That should connect to the Ignition 1 (run circuit)
An easy way to do that is a piggyback on the ballast resistor. It should be a 0.5 Ohm resistor. A '74 originally had a 5 ohm resistor as well. You don't need that unless you are using an original ECU from that time period.)

On the pentagon plug, the wire to the left connects to the coil negative. That's all that's required.
The two wires on the right go to the distributor. They carry the signal.

Your ECU harness has different colors than factory. Doesn't matter as long as you identify them based on their position on the pentagon plug.
And tell us too.

 

[19Dart74]

Yes the distributor is turning with the crank. I can certainly check for spark in the distributor. I did buy a new distributor as well.

 

[19Dart74]

So I believe I've found a problem. I believe that the coil positive is supposed to come closer to battery voltage when key is in run. Instead it goes from near 7 volts with key on and then to near .5 volts in run. Definitely doesn't seam right...

 

[Mattax]

So I believe I've found a problem. I believe that the coil positive is supposed to come closer to battery voltage when key is in run. Instead it goes from near 7 volts with key on and then to near .5 volts in run. Definitely doesn't seam right...

Yes and no.

In start, the battery shouldn't drop below 9.5 Volts. This is measured at the battery.
The voltage difference between the battery positive and the coil positive in start should be pretty small. Off the top of my head, a half volt. You can check this two ways.
1. Measure the voltage across the battery with voltmeter while starting. Then repeat or at the same time measure voltage at the coil. Subtracting will indicate voltage drop in the wiring and ground.
2. Measure the voltage across the battery while starting. Then measure voltage between the battery positive and the coil positive while starting. That will show voltage drop in the wiring.

Voltage across the battery during starting shows the condition of the battery.
Voltage drop in the circuit indicates resistance to the amount of current flowing.

 

[Mattax]

I believe that the coil positive is supposed to come closer to battery voltage when key is in run. Instead it goes from near 7 volts with key on and then to near .5 volts in run. Definitely doesn't seam right...

No.
In run, the coil is supplied power through the 0.5 resistor. Its purpose is to reduce the voltage at the coil positive. This keeps the coil from overheating. With the engine running power is available from the alternator (14 Volts). Just like a light bulb being supplied power at a higher voltage, the coil will draw more current and get hotter than it should. The resistor is bypassed at start because the battery is at best going to supply power at 12 volts, more likley 11 volts and sometimes even less.

This explained on pages 4 & 9 Ignition System Analysis (Session 259) from the Master Technician's Service Conference

 

[67Dart273]

So I believe I've found a problem. I believe that the coil positive is supposed to come closer to battery voltage when key is in run. Instead it goes from near 7 volts with key on and then to near .5 volts in run. Definitely doesn't seam right...

I do not understand what you said.
With key in "run" position and engine stopped, coil + should read anywhere from 6 to 10V This is because the 12V from the battery is dropping down through the ballast to the coil, and the module should be causing the coil to draw current
The coil neg should be anywhere from say, 1/2V to 1 1/2 V which means it is drawing current and close to ground, via the module.

MODULE MUST BE GROUNDED

In "start" the coil + should be very close to "same as battery." this means that if the battery is "say" 11V while cranking, then the coil should be 10.5 or more to 11V while cranking

I'm with everyone above. DISconnect everything from the coil except the two wires into one terminal that should be there with the eyelet on the + side

and the one (black?) on the neg side.

If you have a tach DIS connect it for now. DIS connect the capacitor for now which is for radio supression mostly

 

[19Dart74]

I have spark coming through the coil tower but no spark coming from the distributor to the spark plugs... I'm getting super frustrated...

 

[cudamark]

Sounds like you may have a bad rotor now.

 

[67Dart273]

I have spark coming through the coil tower but no spark coming from the distributor to the spark plugs... I'm getting super frustrated...

OK look you have to be SPECIFIC. What exactly is your test setup, EXACTLY. Do you have power jumpered to the coil +? Or are you using the key "twist to start?" Or are you jumpering the starter solenoid to get it to crank?

What did you use for a coil wire and gap in the test. What did the spark look like? How big/ how long, and are you using a SOLID WIRE as I suggested?

In other words, do you have "just a spark" or do you have a nice strong fat spark?

As someone suggested, If you ACTUALLY have a really good hot spark, at the coil, and FOR SURE none at the plugs, then a bad rotor, cap, or coil wire might be the cause.

BEAR IN MIND that the distributor moves at 1/2 crank speed so make certain you crank it long enough that it actually "came around" to whatever plug you are checking.

If it might be rotor, or you don't no, NOW try to eliminate a PLUG or WIRE(s) as the problem. Take and rig a test gap and SOLID wire to a plug tower and re-test.

 

[19Dart74]

OK look you have to be SPECIFIC. What exactly is your test setup, EXACTLY. Do you have power jumpered to the coil +? Or are you using the key "twist to start?" Or are you jumpering the starter solenoid to get it to crank?

What did you use for a coil wire and gap in the test. What did the spark look like? How big/ how long, and are you using a SOLID WIRE as I suggested?

In other words, do you have "just a spark" or do you have a nice strong fat spark?

As someone suggested, If you ACTUALLY have a really good hot spark, at the coil, and FOR SURE none at the plugs, then a bad rotor, cap, or coil wire might be the cause.

BEAR IN MIND that the distributor moves at 1/2 crank speed so make certain you crank it long enough that it actually "came around" to whatever plug you are checking.

If it might be rotor, or you don't no, NOW try to eliminate a PLUG or WIRE(s) as the problem. Take and rig a test gap and SOLID wire to a plug tower and re-test.

I am using the key twist to start. I disconnected the top of the distributor from where the coil tower connects and used the end as a test gap. My test today ended up as an inconsistent thin white spark approx 1/2 inch long.

 

[67Dart273]

I am using the key twist to start. I disconnected the top of the distributor from where the coil tower connects and used the end as a test gap. My test today ended up as an inconsistent thin white spark approx 1/2 inch long.

Then I would monitor the coil positive with a meter, or jumper power direct from battery and retest

It pretty much has to be (in no order)

1...Low voltage/ poor connections in harness to coil+ or module
2...bad coil
3..or bad module or POORLY GROUNDED module