Low voltage to coil

[Tony 69]

Last weekend I thought I had a coil or module acting up. Breaking up at high rpm.started checking it out today and discovered the voltage to the coil is about 3-8 but mostly 3 volts and jumping around like crazy.

Alternator good at 14v. Also 14 at ballast.
But the coil wire goes into a harness so I think it’s on the inside.

I can’t find the pinout for the bulkhead connector but I took it loose and inspected it. Still clean with die electric grease since I cleaned it 3 years ago.

I’m not sure what the “complete “ ignition circuit should start and end since it was converted to electronic ignition.

Any info would be greatly appreciated and save me a lot of time.

69 roadrunner 440

Thanks

 

[Tony 69]

It looks like the previous owner put the reduced voltage side of the ballast to the orange box. Shouldn’t it have 12 volts? And the coil wire is but connected to a blue wire that goes inside. Crazy this is it has worked for three years and is working today.

 

[HALIFAXHOPS]

Might be the box crapping out. By the look of the transistor, it is a "authorized: box

 

[Tony 69]

I agree about the box. It the coil voltage does not come from the box (?)

 

[Nacho-RT74]

I agree about the box. It the coil voltage does not come from the box (?)

No, from the ballast while in run, but straight from ign switch (bypassing ballast) while cranking.

 

[Tony 69]

Ok
I think some wires are backwards.
Key on engine off
The ballast side with the 2 wires has 6.5 volts. The other side with one wire connected to it has 12 volts. And that’s going to the box. 6.5 volts at coil. But not while running

 

[Tony 69]

And my coil wire goes inside and is not hooked up to the ballast

 

[Nacho-RT74]

In run, the box gets the power spliced before the ballast, so gets 12 volts.

Coil gets the power after the ballast. On the side with brown wire. This mean it could be any voltage between 4 and 9 volts… or something like that, depending on temp and load sucked by the coil while engine is revving.

While cranking is reversed, box gets power from the ballast feedback while power is being sent on the ballast bypass circuit

 

[Tony 69]

I’m still confused about this.
While running my coil gets 3-8 volts and fluctuates a lot. And the wire that feeds the coil is not connected to the ballast. Only the box is. So the wire that feeds the coil appears to be going the the bulkhead connector.
the coil voltage stays mostly at 3. The alternator voltage does not fluctuate.

??

 

[Nacho-RT74]

 

[Tony 69]

So ignition 1 is start and ignition 2 is run

 

[Tony 69]

I thought the coil get 12 volts cranking and 9 volts running
The diagram doesn’t show how this is possible

 

[twecomm]

On the ignition switch, when key is twisted to "start", or cranking position, a full 12 volts ( battery voltage) is applied to the coil. The ignition switch, in this start or, cranking position electrically bypasses the ballast resistor. When key is in the run position, the ballast resistor is then "in the circuit" path to the coil. and 12 volts is no longer applied and voltage is reduced by a few volts to LESS than 12 V applied to the coil.
Could be a defective ignition switch. Also the wires associated for this entire path do go thru the bulkhead connector. as well.

 

[72RoadrunnerGTX]

So ignition 1 is start and ignition 2 is run

No, ignition 1 is run (full voltage in the run position only), Ignition 2 is the resistor by-pass (full voltage in the crank position only).

 

[RJRENTON]

I agree about the box. It the coil voltage does not come from the box (?)

The ECU (aka "box") switches, via the transistor, the coil's pfimary current and subsequently the coil's primary voltage. When the box switches OFF, the coil's magnetic field collapses, creating the spark. As soon as the spark pulse occurs, the box's internal dwell circuit turns ON the transistor to recharge the coil for the next turn OFF cycle for the next spark.....etc....short answer: YES the coil's currrnt AND voltage go thru the "box".....thus ends the lesson.....
BOB RENTON