Petronix replacement for points

[johnharrill]

It's magnetic, hooked up to the violet and green wires from the MSD.

Tonight, I checked the primary and secondary of the coil (in spec), checked the ground, and hot to the MSD. Re-made the connection on the main power (heavy red) wire to the unit for good measure. Then, took a test drive.

Cooler than before. However, this trip around the neighborhood resulted in three failures in the space of 20 minutes. The problem is getting worse. Each time, all electrical power stays on in the car, but the engine dies. It re-starts immediately. I don't think it's fuel.

To the idea of testing the MSD on the bench: Who does that?

[Stefan2000]

As said, it's not impossible that the MSD is causing problems.
The only real reason, from what i've encountered, for MSD systems to malfuction is when it does not have a good ground connection. Than it will discharge via the magnetic sensor, while that is connected to ground via the distributor and fry the magnetic pickup or damage the circuit board.

But than still by far your cheaperst option is to swap out that magnetic pickup for a new one (some 50 bucks) and replace the MSD with for example an MSD streetfire unit (some 300 bucks) and your good to go. Than you still have CDI ignition and a rev limiter.

I could test the complete system for you. i would just put your complete system on a distributor testbench and let it run for an hour and see what happens.
But you could do it yourself as well in a slightly less advanced way, just wire everything up on a workbench and connect it to a battery, put the distributor in a vice and drive the distributor with a drilling machine.

Testing it this way ensures that all the 'car related electrical components' like electrical connections, ignition switch, voltage regulator etc. etc. are out of the equation and your only testing the ignition system.

[johnharrill]

More interesting symptoms.

During one of the failures we had on Tuesday, when the engine died we cranked the car and watched the red LED on the MSD. It illuminated solid while cranking, that is, it did not pulse as expected and the engine did not start. Then, we turned off the key off and back on again and cranked it again. This time, we saw pulsing of the LED and the engine started.

This might indicate that (a) the ignition switch is intermittently failing to provide power to the MSD or (b) the magnetic trigger is intermittently failing.

The plan this evening is to put a test lamp on the wire from the switch to the MSD box and watch it when the engine dies. If the lamp goes out, it's likely the switch. If it stays lit, my suspicion falls on the magnetic trigger.

If I need to replace the trigger, which should I choose?

[Stefan2000]

You can just use the standard MSD magnetic pickup. It's partnumber 84661 and it will more or less just bolt in place in an original distributor.
Is that also the one you have in there currently? And you must have some sort of reluctorwheel in there as well, how is that one adjusted? It should have a gap of around 0,5mm between sensor en reluctorwheel.
Attached a picture of what i use, the MSD magnetic pickup and a custom reluctorwheel that fits over a rigid shaft and over the 3 lobe cam, depending whether you use a programmable or standard MSD.

[johnharrill]

I do have a pick-up and reluctor wheel. Today, I replaced the ignition switch and started the car. It ran for 5 -6 minutes and then cut off. The failures are now every few minutes. Just seems electronic in nature.

Attached is the magnetic trigger and reluctor in the distributor.

Can the trigger bet changed without a lot of disassembly?

[Stefan2000]

It does not really look like a genuine MSD magnetic pickup but more like a magneti marelli magnetic pickup as was used in many of the older italian cars from the 80's.
I would not be surprised if the actual MSD sensor has a better signal (at low rev's) while it comes with a big magnet underneath the sensor which i assume creates a larger magnetic field.

You could try to replace your sensor with a new Magneti Marelli one, or spend a bit more time and convert it with the MSD sensor. It could be that you cannot use your current reluctorwheel in that case but than i can help you with a new one that will work. Is your current reluctorwheel placed over the original 3-lobe cam or did they machine that cam in order to make it fit?

[johnharrill]

No history is available on the reluctor wheel, as the prior owner has passed away.
I did mange to remove the pick-up and it has some corrosion on it. So, I think I will get a Pertronix Ignitor II. It is supposed to be a direct fit.

[Stefan2000]

Worth a try.
Just FYI, ALH (on this forum) did quite some tests with different sensors and does not recommend the Petronix because it has several degrees of timing difference between the magnets.
https://www.ferrarichat.com/forum/threa ... -149288113 -> #37

[johnharrill]

I'm thinking that the previous owner did quite a few modifications to install the components in the distributor. The circlip to hold the ball bearing on was missing and when I tried to remove it, the bearing disintegrated, leaving behind the collar still pressed onto the shaft.

Now that I have a clear view of the reluctor wheel, it appears to held on with some sort of roll pin. I'm not sure how to remove it. I'll post photos shortly.

[johnharrill]

Here is the photo. The spring pin/roll pin can be seen on the wheel at about 7 o'clock.