Electronic ignition - Revisited after I gave up!

[Arne]

Well, I can't seem to leave this alone.

I did some testing a few weeks ago that indicated the Pertronix Flamethrower 3.0Ω coil was not up to spec. I put it in the car for testing and it actually failed. No start, no run.

OK, a totally failed coil I can understand. As a replacement I bought a Crane PS20, which is rated at 1.4Ω and includes a matching resistor in the box. Thought maybe I could get it to work this way. (When will I learn?)

Still failed. In fact, the combination of Pertronix Ignitor with the Crane coil & resistor may have been the complete low point of all my testing through the past 3-4 years. It was hard pressed to rev much beyond 3000 RPM that way. Bypassing the resistor made it drivable, but still washed out at 4200 or so. Total waste of time.

And here's the part that always gets me - while my car runs fine on points with the stock (40 year-old) coil and resistor, it does NOT run fine with those same points firing one of the other coils. I could get it to run pretty well on points with the Crane coil if I bypassed the resistor, but with the resistor in place (as it really should be used with points) I got much the same result as with the Pertronix Ignitor in place.

In other words, my car only runs right with all its factory ignition parts. Change any one of them for something "better" and the car won't rev out. This is troubling to me - someday that 40-year old coil will die, and nothing I've tried to use in its place so far has worked.

So far I have tried:

Distributors:

• Factory 1971 240Z distributor (D612-52) with stock points
  
• Factory 1971 240Z distributor (D612-52) with Pertronix Ignitor
  
• Factory 280ZX w/E12-80 (two different examples, each tried with more than one module)

Coils:

• Factory 1971 240Z coil (1.6Ω)
  
• Factory 1982 280ZX coil (used)
  
• Aftermarket stock replacement 280ZX coil (new)
  
• Pertronix Flamethrower coil (3.0Ω)
  
• Crane PS20 coil (1.4Ω + included resistor)
  

The only config that works flawlessly is all stock with points. The Ignitor/stock coil/bypassed resistor is close, but I dislike not running the resistor because I fear the increased voltage through the inductive loop on the tach could possibly hurt the tach over the long haul, plus I don't know how that coil might hold up at full voltage all the time either.

It would be interesting to try a ZX dizzy again, as I've learned a bit more about my car's behavior now. But I sold that stuff long ago, and I am really getting a bit tired of spending money chasing the ideal ignition, when what I already have now is good enough.

Edited June 12, 2011 by Arne

[soundmasterg]

If you're interested in a backup Arne I have a NOS in the box coil for a 240Z. Let me know via PM (or I may forget to check here) and I can bring it to the show tomorrow if you want to look at it.

Greg

[alhbln]

The Bosch red coil/ballast resistor (0 221 119 030) works well as a replacement for the factory coil, it has the same primary resistance and will even give a bit more output.

[FastWoman]

Arne, I really don't run my engine up in the 6k range, so perhaps I haven't really challenged my ignition a lot, but I've been very happy with my stock '78 distributor, an MSD Blaster II ignition coil (no resistor), and a GM HEI ignition module with a big heat sink on it. It's not very sexy, but it's worked great for a year now. The HEI module was CHEAP -- $11, as I recall. There are more expensive ones for higher performance, as I understand.

[Arne]

Thanks for all the suggestions, everyone. I still don't know where I'm going to go on this. I don't really NEED to convert - the points and stock coil work fine for my purposes. But it nibbles at me, and eventually I have to take another try to make it work.

Obviously, there are far more options available than I have used thus far. But I am - as always - hampered a bit by my desire to maintain either stock or period-correct appearance, even under the hood. That desire eliminates a whole lot of choices...

Edited June 13, 2011 by Arne

[Arne]

Tried something new today - re-installed the Crane coil only, left the points and factory resistor in place. But I bypassed the tach. Went from the "resisted" end of the ballast straight to the positive terminal on the coil. Took the tach and that long run of wire out of the loop. Result? Same as before, started cutting out at high RPM. Re-installed stock coil, all is again well. So that looks to eliminate the tach circuit as a cause.

I think I'm fighting two different issues on this. One of them still seems to be insufficient voltage to recharge a higher output coil quick enough at high RPM. This is what gives the problem with aftermarket coils when used with my points.

But I also have issues with the Pertronix when used with the stock coil. And there I believe that the dwell time on the Pertronix is too short - again leaving the coil insufficient time to recharge before the next spark is required.

Which is why combining the two (Pertronix and hi-output coil) typically works so badly.

Will probably do some voltage checks at the coil with the engine running later today.

[Arne]

Well, there goes one more theory.

Checked voltages.

Ignition on, engine off:

• At battery - 12.8v
  
• At hot side of resistor - 11.2v
  
• At resisted side - 5.9v
  

Aha! Looking like I may have an issue.

Until I checked with the engine running:

• At battery - 14.5v
  
• At hot side of resistor - 14.0v
  
• At resisted side - 11.2v
  

Back to the drawing board...

[steve91tt]

Did you try the voltage measurement as a function of RPM? Maybe my logic is incorrect but I'm thinking more RPM means more current and therefore the potential for voltage drop as the components could become resistive with higher current draw. You might also jump straight from the battery to the resistor with a fresh wire, temporarily, for testing purposes.

[240dkw]

Arne: Have you tried replacing one or both of the capacitors.Your High-output coil problem could be caused by a faulty capacitor, I copied this from another web site." When the points open the capacitor is connected in series with the coil. The voltage/current generated by the collapsing magnetic field charges the capacitor. This is the voltage/current source that is induced into the stepped up secondary winding. A coil opposes current flow while a capacitor enhances current flow. The enhancement of the capacitor balances out or cancels the opposition of the coil. The result is a faster collapse of the magnetic field and the highest possible voltage generated in the primary circuit. It's true that the capacitor reduces or prevents arcing at the points but its main function is to provide a circuit path for the coil after the points open and to speed up the collapse of the magnetic field."

Dan

[Arne]

Hmmm. That's a thought. I normally have not been hooking up the condenser on the dizzy when I try the Pertronix in it, but I have been connecting the condenser on the coil, in all cases. I seldom use the radio, perhaps I should try the Crane coil without?

[Arne]

Well, apparently the condenser/capacitor/whatever that connects to the negative terminal of the coil is a required part. The car will barely run w/o it. And since it is original, I'd like to replace it. It does not show separately in the factory parts book, appears to come only as part of the "Ignition coil assy." Any ideas on where to source the correct part?

[Walter Moore]

Interesting... you have a capacitor between the negative side of the coil and the frame? Is that shown in the FSM? I never had a capacitor there, even when I was running points. Now that I have the S130 distributor (and a stock S130 coil) I have no capacitors in the ignition system at all. (Except as they may exist inside the E12-80, but those can't be very large if they exist at all)