1974 260Z ignition coil wiring help / ignition module

[Shawninvancouver]

I have a brand new msd coil. when car key is turned on i have power to a black/white and blue wire / are they both supposed to have power??  I need to know which goes to the negative and which goes to the positive on the coil  - the wire diagram says black/white to pos and other to neg. i tried that and when i turn key to ignition nothing happens.. tried wires other way and nothing happened. i am very close as i have power going right to the coil but not coming OUT of coil.. i checked fusable links.. all look good..
what is wrong here?? the way the wires are hooked up? or is there something else im missing??  does my car have a electronic ignition module under dash?? if this is bad what will happen>>?? wiill i still get power on both wires up to coil???

please help
thanks..
photos below..

[SteveJ]

You said you're not an electrician, and now you're making me break out the electrical engineer.

The coil is a step-up transformer. You are going from 12VDC up to 30,000 VDC or higher. The higher voltage will be induced when you have a complete circuit on the 12VDC side. However, if you have a complete circuit all of the time, you won't develop the magnetic fields on the primary side to induce the voltage on the high voltage side. When the engine is turning, the reluctor passes near the pick up coil in the distributor, and it creates a signal for the Transistor Ignition Unit to ground the blue wire. Current flows, a magnetic field is developed on the primary side, a voltage is induced on the secondary side, that induced voltage is at a high enough potential to overcome the resistant at the gap at the spark plug, and you have your spark.

Now don't worry about much of anything in the previous paragraph until you REALLY want to understand ignition systems. 

With how you measured, you don't have power on either side of the coil. Power is voltage and current. You measured voltage on both sides of the coil. No, I'm not being pedantic. I hope this comes clear in a minute.

In it's normal state, the ignition system is an OPEN circuit. With the key in the ON or START position, you are connecting it to the positive side of the battery. There is nothing connecting the ignition circuit to the negative side of the battery (ground) until the TIU connects it to ground. The primary side of the coil is just a long piece of wire, so it will have essentially the same potential at any point in that circuit.

So the short answer is that you are using the meter properly, and you're probably seeing the voltage you should be seeing.

If you are wondering whether or not the TIU is working, pull the coil wire off the distributor, with the coil wire connected to the coil. Position it close to one of the bolts on the shock tower (like about a 1/4 inch or so). Try to start the car. You should see the spark jump between the coil wire and shock tower.

[Shawninvancouver]

Hi steve - im hoping i can get through this. 

- it is a brand new coil  -- I was doing what you said in your last paragraph.. taking the coil wire off from the distributor cap. but instead of holding in near a ground area on the car looking for spark - - i was using my screwdriver with a light bulb in it ( electrical tester ) hooking to end of wire from coil and poking to a ground - assuming i would see the bulb light up if i was getting a spark.. would that work? or would it not show the screw driver light up??  does it need a gap? is that why i as not seeing screw driver light up?  and to recap - two simple questions?

1. so there should be constant power to both pos and neg of coil?

2. does the black/white go to pos or neg? ( i looked and fsm but does not show on coil diagram ) 

3. is there any module under the dash? or only for electronic ignition and not points?

 

thanks a million

Edited June 5, 2021 by Shawninvancouver

[SteveJ]

6 hours ago, Shawninvancouver said:

Hi steve - im hoping i can get through this. 

- it is a brand new coil  -- I was doing what you said in your last paragraph.. taking the coil wire off from the distributor cap. but instead of holding in near a ground area on the car looking for spark - - i was using my screwdriver with a light bulb in it ( electrical tester ) hooking to end of wire from coil and poking to a ground - assuming i would see the bulb light up if i was getting a spark.. would that work? or would it not show the screw driver light up??  does it need a gap? is that why i as not seeing screw driver light up?  and to recap - two simple questions?

1. so there should be constant power to both pos and neg of coil?

2. does the black/white go to pos or neg? ( i looked and fsm but does not show on coil diagram ) 

3. is there any module under the dash? or only for electronic ignition and not points?

 

thanks a million

You would want to test it the way I described. Your testing would not yield good results.

1. With the ignition in ON, you would see voltage to ground at the positive and negative on the coil, except when the TIU is triggered by the distributor. (This is on a properly wired/functioning ignition.) 
2. For a stock configuration, it should be a white/black wire on the positive. The blue is on negative, as in your photo. The white black should go to the ballast resistor. There should be a black/blue on the middle terminal of the resistor (starting) and black/white on the opposite end of the resistor (running).  
3. The TIU is in the passenger footwell, likely on the firewall.

Now, for the stray wire in your photo, you would have to clean it off enough to tell me what the wire color(s) is. My first guess is that it might be one of the wires that goes to the ballast resistor.

[Shawninvancouver]

Hi steve, after more work today i can tell you the following.. we cant get spark.

when the key is turned on the only wire getting power is the black/white.

i put that black/white  to the + on coil - blue to neg coil.  also attached to the black/white is a black/green  i think... ( not mentioned in manual) in my photo..

also -its electronic ignition... i took a photo of the Ignition control unit.. a bit rusty  

also there is no mark for spot 1 on distributor cap..

 

we held end of coil wire to ground when trying to start and no spark...

where do i go now???