MSD box takes a dive, (rant).

[6667fan]

I bought a used 7AL-3 at the FE R&R two years ago. Even though it was advertised as being freshened I sent it out to them last September along with a 6 box that needed work. There were only a few small things wrong with the 7 which MSD fixed. I ran the 7 all this year without incident until a few days ago. Engine had been lighting off easily and running well. I had pulled Fairlane out of shop for some work on a wide-band sensor. Go to put it away and cranking fine but no firing. Just in case the voltage to the unit was low I added in a 55 amp booster jump to battery. I could see on my volts gauge I had over 12 while cranking so plenty of juice for the sometimes finicky 7 box. Not even a pop.  Ended up just wiring my 8595 RTR distributor without box to get car back in garage. ( Lit off no problem).

Did the standard spark jump test after confirming the box was getting juice while cranking. No spark. Substituted a Blaster II coil to rule out the hi voltage 8251 coil was the problem. No difference, no firing.
So now the 7 is going to go back to Texas for another refresh. So irritating 😠

[Rory428]

Just curious if you know the vintage of your 7AL? I have been running the same MSD 6T ignition box in my Fairmont for over 30 years, with zero issues. The 6T required a separate "Soft Touch" rev limiter , and was later superceded by the 6AL model with a built in rev limiter. When I built my 85 Mustang NHRA Stock Eliminator racer,in the early 2000s, I bought a new MSD 6AL, which worked fine for a couple of years, before it just died, and quit running. So I bought another new 6AL, and raced for another 5 or 6 years, before that one died as well. Bought a 3rd 6AL, ran the car for another few years, before selling the car. So one 6T still working for 30 years, while the 6ALs needed 3 units, to go 12 years. So much for "new and improved". No idea how the later Digital MSD boxes are holding up. Did you send your MSD boxes back to MSD, or an outside facility? I understand that a company called Southwest repairs/upgrades MSD boxes, I guess I should send my 2 dud MSDs down for repair, not worth anything as they are, sitting in the garage .

[6667fan]

Rory, I don’t know the sequencing of the 7 series. Mine is a red box. There is also a gold box 7 series. I don’t know the order of release or the differences.
I send them directly to MSD after getting a number from them which is to be written on the shipping container.

They will tell you, ( if you ask), the max dollar cost that you may incur for a particular box. So at least you know going in what the ceiling might be.