Electronic distributor made a buzzing sound

[tg3690]

Was going to start my motor on muffs with the cowling off......turned the key on and pushed in for the choke. Then I noticed a faint buzzing sound coming from the distributor. Then it stopped. I hit the choke again, and it did it again, briefly. Have never heard that noise before. I went ahead and started the motor, and it seemed fine. It has the Motorola Magna Power I ignition with electronic distributor and CD module. I replaced a faulty preamp last year with a brand new one. Besides the preamp, there's not a lot of stuff in there to cause problems, other than the rotor/shaft and cap. Took the cap off and didn't see anything suspicious....Nordin or jerry, got any thoughts on this?

 

[Nordin]

Never have experience of buzzing sound from the distributor.
Do you have the OEM preamp or a preamp from CDI Electronics?
Very early Magna Power CD boxes from Delta with the two transistors mounted outside the box and this is when the Magna Power was introduced in 1967-1968 and they were on the 75 and 105Hp engines.
Chrysler then used CD boxes from both Delta and Motorola.
From early 70es most CD boxes were from Motorola I think.
These early Delta CD boxes will get a pinching sound from it when power it, the same is the aftermarket CD box from CDI Electronics part number 115-3301.
It also will get a pinching sound when powered.
The sound is created from the power transformers inside the box and normal for these CD boxes.

 

[tg3690]

Never have experience of buzzing sound from the distributor.
Do you have the OEM preamp or a preamp from CDI Electronics?

I have never heard that sound from a distributor, either. I got a brand new OEM preamp from Franz. I had to take the rotor/shaft out to replace the preamp, but it went back together fine and is running good. Before it stopped making that noise I was able to put my ear up to the distributor and it was definitely coming from it. It didn't sound like an electrical short or wires burning or anything like that. No smoke or signs of anything getting hot. I guess I will take it out and run it and see what happens. There are trouble shooting steps in my manual I can do, but like I said the motor starts and runs good.

 

[Nordin]

Okey, do not think a troubleshoot will give any answer.
It only cover if you have problem with the ignition.
If it works and will sound when you start it up just run it.
That is what I would do if it was mine engine.
Maybe time to catch up one for spare.
The bad think is they are pretty expensive now, OEM or aftermarket.

 

[jerryjerry05]

Honestly I know very little about the older ignitions. When I started working on outboards all I did was the newer stuff starting at 1984.
Here's a link to Mastertech Marine, Guy named Bill Kelly answers the tough stuff, Good luck!!!
https://maxrules.com/ChryslerModels/chrysmodelindex.html

 

[Nordin]

Yes, try Bill Kelly and why not Franz Buddenberg at Franz Marine Service.
Franz is a Chrysler/Force guru.

 

[tg3690]

Nordin and jerry, thanks for replying. I wanted to run this by yall before I started making calls. I have talked to both Franz and Bill Kelly in the past.....they are a dying breed for sure when it comes to the old school knowledge of these old motors. Last time I talked to them they were both trying to retire and I really can't blame them. I will try to contact them and see what they think about this. Appreciate the help, gentlemen!

 

[tg3690]

Yes, try Bill Kelly and why not Franz Buddenberg at Franz Marine Service.
Franz is a Chrysler/Force guru.

Nordin, I called Franz just now.....he is still in business.....says he has too much stuff to sell and get rid of before he can retire. That is good news for those of us who still run these old engines and need help from time to time. I don't mind paying more for his parts because he will answer any questions you may have about whatever issue you are dealing with. That is a rare thing these days.....

I asked him about the buzzing sound coming from the distributor.......he said the only thing he could think of was maybe the position of the rotor when the key is turned on. If the rotor was parked on or near one of the contact points in the cap it might be arcing a little bit, causing the sound. And if that was the case it wouldn't be a concern. He said to run it and see how it goes. He said he has the parts in stock to repair it if it comes to that. I will post an update if there are any new developments. Thanks......

 

[Nordin]

But, but there is no points in the distributor as it has the preamp.
The electronic distributor has a disc with 3 windows in your case as it i s a 3- cylinder engine.
The disc is running through the preamp and the photo electric diod in the preamp is "reading" the windows and trigger the CD box.
In the no electric distributor the points is trigging the CD box.
A 3-cylinder engine with points will have a cam lobe with 3 cams and a 3 cylinder with preamp will have disc with three windows.
A 4-cylinder will have four of these cam lobs and disc windows.
No arcing if you have an electronic distributor from my experience, maybe arcing between the center tap to the rotor or between the rotor to the contacts to the HT-wire terminals in distributor cap.
Updated: Read your post more carefully and no mention about points, my mistake. Sorry, sorry.

 

[tg3690]

Hey, no problem at all. I guess what Franz was saying is that if the rotor was parked on or near one of the HT-wire terminals in the cap, then one of the 3 windows in the disc would be in the correct position to fire the CD module? Does that make sense? I can't remember which position (open or closed) triggers the CD to fire.
I reread my own post and used confusing words to describe the HT-wire terminals in the cap.....I called them "contact points" in the cap. That didn't help any at all! My bad......

 

[Nordin]

Yes that maybe is possible.
I also do not know if the triggering of the CD box is when the photo diod in the preamp goes from covered to uncovered from the disc or from uncovered to covered by the window.
The troubleshooting says if I do not remember wrong to use a credit card to simulate the disc to cover and uncover the photo diod.
I think is does not matter, think I have read somewhere but do not remember where that the OEM preamp handles one of the scenario and the aftermarket from CDI Electronics goes the other way.