Pertronix Ignitor I won't rev - Alternative solution

[SteveJ]

A friend installed a Pertronix Ignitor I into his 240Z, and he contacted me for help since he could cruise fine at low RPM, but whenever he tried to get on the gas, it would stumble and cough. He thought it might be a coil impedance issue so he tried various coils but kept having the same issue (and sometimes even worse performance). Since he has been wrenching on Z cars since the mid 80s, I figured he had gone down the wrong rabbit hole at some point. I loaded up the rescue wagon and headed over to his place.

The first thing I did was connect an oscilloscope to see if I could pick up an obvious miss. The scope left me with the impression that something wasn't happening right as higher RPMs. (I might recreate his problem on my 240Z and see if the scope shows the same thing. If it does, I'll make a video to help people with diagnostics.) I looked at the resistance to chassis ground at the distributor. The resistance was nearly zero, so it wasn't a grounding problem. From some old threads here, I thought the vacuum advance might be an issue. Unfortunately his hand pump would let me pump up enough vacuum to check, so that was tabled. Next was inspecting the distributor cap. The contacts were clean as was the rotor. So I moved to inspecting the posts where the wires land. The wire on the center post wasn't seated far enough down, so I pushed that in. Then I pulled off each wire one by one, starting with #3 and working clockwise. It was good, #5 was good, #1 was good, #4 was good, but #2 was not. The boot was almost off the wire. There was no way it was getting a good spark. I positioned the wire properly in the boot and re-seated it. Then I checked #6. It was good. I looked at the scope again. It looked better, but I didn't shoot video.

After my friend fixed a fuel leak at the banjo fitting on the rear carb, (The fitting wouldn't seal, so he replaced it.) he took it for a spin. He said there was no hesitation, and it pulled hard past 5,500 RPM. 

The moral of the story is that when you can't figure out what's wrong, step back and go over everything from the beginning. Sometimes you have to eliminate each and every variable until you have the solution.

I love getting another Z back on the road.

[Diseazd]

Great job Steve…..I changed points once and the car wouldn’t fire. Took me 20 minutes to figure out that there is a little piece of protective paper between the new point contacts……🤪

Edited September 19, 2022 by Diseazd

[SteveJ]

1 hour ago, Diseazd said:

Great job Steve…..I changed points once and the car wouldn’t fire. Took me 20 minutes to figure out that there is a little piece of protective paper between the new point contacts……🤪

That's the thing. Any of us (and that includes me) can make those little mistakes, often times not even realizing it happened. I've done things like try to start the car without the wire on the coil or with the rotor sitting on the fender. When it's not as obvious, it's easy to get frustrated and start loading the parts cannon to replace all of those bad parts that aren't really bad.

In my friend's case, I could hear his frustration as he repeatedly swapped in parts with no success. That's why I went over to his place with the plan of getting a baseline and examining each part and correct each issue I encountered. This time, it was an easy solution.