I ran across an odd problem this morning on my Jensen (w 74 440), while working with some wiring under the hood with the ignition on, my MSD 6A box starting making a high pitched buzzing noise - almost squealing noise. Its intermittent, but I can make it happen by wiggling the wiring to it. I think Ive narrowed it down to something on the distributor mag. pickup circuit. If I disconnect it from the distributor, the noise will go away for good, but as soon as I reconnect it, the noise will come back.

I isolated the wiring for this, and tested it for any shorts or problems, it seems to be fine. I measured the resistance across the pickup leads at the dist., I got about 250 milli-ohms, but im not really sure what I should get there.

So pretty much Im trying to decide if this is being caused by the MSD box itself, or something external like the distributor. I did bump the engine over to make sure it wasnt something inside the distributor that was in a certain position, didnt change anything. Unfortunately I cannot run the engine right now, so I can't say if it is functional or not.

Sorry about the length, thanks for any help!

Quote:

---

I measured the resistance across the pickup leads at the dist., I got about 250 milli-ohms, but im not really sure what I should get there.

---

You should be getting 375 to 450. I would wait till you can run the engine before changing anything out, but that ohm reading is low.

I assume the engine was not running... if it was sitting at just the right spot on the pickup where it was about to trigger or not it might be randomly sparking...

I would try pulling the trigger and see what it does.

Also I would not be playing around with the wiring with the MSD box on... could be asking for shocking events...