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Ignition coil specs for 240Z


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Hello everyone, greetings from Mexico City. My 240Z has been stored for a number of years and I´m decided to finally start working on it (a number of personal issues had prevented it so far) I have another post with its presentation in this club and received great feedback and some nice tips regarding a first restart of the engine after years of inactivity. Among the things I´m planning to do is an engine tune up and connect everything as the factory indicated. The engine is pretty much stock but it seems a couple of things have been fiddled with (for example, there is no ballast resistor, it seems to have been removed, a couple of wires are disconnected, etc) At some later point I intend to switch to an electronic ignition but right now I just want it to start and run on factory specs in order to diagnose the engine´s condition as precisely as possible. I already have the usual parts; points, condensers (the car is automatic), distributor cap and rotor , new ballast resistor (rated at 1.5 Ohms I think) spark plugs, spark plug cables. I still haven´t bought the ignition coil tho, and here´s where I´d appreciate your advice.  Of course there are a lot of places, stores, on line sellers, etc where one can purchase an ignition coil for this car...but it caught my attention that most vendors either don´t publish the coil´s technical specs (most times it just states wheter it will or won´t fit your car model) or when the specs are available, they are not what the FSM indicates. The FSM indicates a Primary Resistance of  1.5 to 1.7, a Secondary Resistance of 9.5 to 11.6 and a 1.6 Ohm external resistor. 

So my actual question is the following; I was browsing through some local sites that published their coils´specs and found a local brand with a model that has a Primary Resistance of 1.6, a Secondary Resistance of 9.5 and require an external resistor of 1.35 Ohms, the application list says it´s meant for older Ford and GMC V8 engines (the Datsun Z cars were never sold in Mexico at that time) My question is: Would this coil work for my 240Z?

Also I found the specs for the Duralast C831 at the local Autozone site and are as follows: Primary Resistance of 1.1 to 1.9, Secondary Resistance of 7.5 to 13.0 and no mention of an external resistor, and its supposed to fit my car according to them. Would this be also a reasonable choice? I really don´t need right now the best brand or model, the highest performance or even durability, I just need the car to perform within "normal" conditions in order to decide what or how much work the rest of the engine needs.

What do you think?

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I believe RockAuto will ship to Mexico. In the US, they are usually cheaper than the parts stores. Anyway, if you are still using points, you need the ballast resistor, or you will burn up your points. Depending upon the voltage you need for the electronic ignition, you will probably bypass the ballast resistor later.

Ballast Resistor: https://www.rockauto.com/en/catalog/nissan,1972,240z,2.4l+l6,1209169,ignition,ballast+resistor,7052 (Helpful hint, if it comes with a jumper wire like what is shown on the photos of the resistors, throw the wire away.)

Ignition Coil: https://www.rockauto.com/en/catalog/nissan,1972,240z,2.4l+l6,1209169,ignition,ignition+coil,7060

This coil has the same specs as the one you saw on the Autozone site: https://www.rockauto.com/en/moreinfo.php?pk=931800&cc=1209169&pt=7060&jsn=1758



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Both of those local coils would probably work just fine.  That's a wide spec on the Duralast coil, but it will probably be in the middle at about 1.5.  Even if it's a little bit low, that's not a huge difference.  Maybe a little extra heat but worst case it will probably just last 50,000 miles instead of 100,000.  I'd buy one of those two coils and just use it with your ballast resistor.  

You'll probably want to check the size on that older Ford/GMC coil if you use that one, it might not fit well.  But it should work with no problems once you get it mounted.

If you have a meter you could take it to the store and verify primary resistance before you buy if it worries you.  Secondary is not as important for longevity, I wouldn't worry too much about that measurement.

Just for fun - 


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With the ballast resistor missing have you verified that the distributor has maybe been swapped to a ZX electronic distributor with either the E12-80 matchbox or the E12-92 matchbox on the distributor? Yes, the E12-92 works just fine. If you only use the same connections as on the E12-80 and don't power the other connections the E12-92 will work exactly the same as the E12-80.

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No. The distributor is still the old point and condenser one. I relly don´t know why they discarded the ballast resistor. I removed the coil and oddly there´s nothing written on it, no brand name, model number or any other indication (for instance, wheter or not it has an integrated resistance, etc) I just got a new one that seems to match the factory specs and a new ballast resistor. I ´ll connect everything as it should (by the way, does anybody have a simplified coil/resistor/distributor diagram? I have the FSM butsometimes it gets a little confusion for me)

Interesting that you mention the ZX distributor swap, latter down the road I hope to switch to an electronic ignition system and it seems like a fool proof option (if I can find one in good shape), if I can´t do that, maybe the 123 Ignition one? The pertronix adaptation is out of the question since it doesn´t seem to work with automatic transmition cars like mine (Am I correct on this?)

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@Captain Obvious posted a picture in another thread recently, but here's the text version of how to do it.

  1. Black/white to the coil positive
  2. Green/white to one side of the ballast resistor
  3. Black/white to the other side of the ballast resistor
  4. Black wire from distributor to coil negative

Now you saw that I mentioned black/white twice! How do you tell them apart?

  1. Make sure the car is off.
  2. Make sure the green/white wire and both black/white wires are disconnected in the engine bay.
  3. Using a multimeter, measure continuity from the green/white wire to each black/white wire.
  4. The black/white wire with continuity to the green/white wire goes to coil positive.
  5. The other black/white wire goes to the ballast resistor.
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5 hours ago, Captain Obvious said:

I added the wire colors to the sketch SteveJ mentioned.


This would make a good addition to the Wiring Diagrams Downloads page, and a few other places.  Documents can exist in more than one place, I assume.

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