Left Me on the Side of the Road! Now What?

So, I'm going to a cruise-in and it just sputters out and dies about 2 miles from home and won't restart. Luckily, it was slightly down hill and all I had to do was give it a nudge to get it into a parking lot.

It will crank, it's getting gas but isn't firing. It is MSD-6AL with small-body HEI conversion. I pulled the tach wire from the MSD, checked the connection from distributor to MSD, checked the coil wires and nothing is loose. Everything seems snug and no obvious issues with that.

My wife brought me a few tools and a volt-ohm meter. I'm getting power to the coil + when it is in the RUN position.

I have a spare HEI distributor, complete with plug wires. I'm going to swap it and run 12V to the battery side to get it home... hopefully.

I figure the HEI is A) self-contained, B) independent of everything else on the car as long as I can jump 12v to it. If that doesn't work, I'm REALLY screwed and will have to have it towed home.

Anyone have any idea how to troubleshoot this? This is the first time it has let me down. I guess I should be glad it is only 2 miles from home.

I'm looking for info on how the small-body HEI can be diagnosed and what I can check on the MSD-6AL to confirm it works.

 

MSD has fairly decent troubleshooting charts on their site.

 

Is the rotor even turning?

 

Yep, did a search and found the way to test. Just for giggles, I tried to start it again and nothing but crank/no spark.

Oddly, when I disconnected the distributor and tried firing the MSD by shorting the trigger wire, it didn't initially fire the coil. After 3 tries it finally hit and would fire the coil every time. I checked the ohms on the distributor trigger and it was within spec.

Again, I checked all the wires and everything looked good. I put it all back together and it fired right up but a bit rough. Maybe it had cooled off and the engine needed to warm up a bit.

It isn't fixed though. Something is still wrong. I got it out into traffic on the way home and when I let off the gas, it started to bounce the tach below 500. I geared down to keep the RPM up and it caught back. At the stop light where I turn for the last 7/10 of mile to my house, it sputtered again.

Finally, I pulled into my driveway and left it running while I moved the 350 car to the other side so I can put the Stage 1 on the lift to figure this out. While I was backing the 350 car out, the Stage 1 slowed and died. It started backup and is in the garage but I don't trust it now.

I'm leaning toward the MSD 6AL crapping out. It is starting make me think that once it gets hot, it has issues. After it cools, it will mostly work for a while.

Yep, one of the first things I checked when my wife brought tools. I didn't have a long enough straight blade screwdriver with me and I was getting fuel so I was pretty sure it wasn't the timing chain or cam gear. Seeing the rotor turn ruled out the rolled pin giving out.

 

Coil maybe acting up when hot?

 

Could be. The coil on the 350 failed about 3 years ago when we were changing from the M21 to the M20 (before the rebuild and M23Z), which was totally unrelated.

I have a spare coil. I'll throw that at it and let it get warm to see what happens. It had run fine for the last 5-6 years in all kinds of hot weather.

 

What’s firing the MSD? I think I know. A pick-up in the distributor. Pretty common the pick-up is the problem. I kept a spare in my race trailer. The damn thing would cause all sorts of weird problems. This is kinda old school now.


I reread your info on this before I hit post. You have an HEI? If correct. All most sure it’s the pick-up

 

So your firing the MSD box via the white wire, and not using the mag pickup to fire it directly?

I had trouble with a few MSD boxes back in the 2002-2010 time period.. the last stand for the analog boxes... if yours is from that time period, I would not be surprised if it's the issue.. since they went to the digital boxes, I have had no issues with them. Have had one in service here for about a number of years.

And I would recommend directly firing the MSD box with the mag pickup (it is an MSD pickup in your small body conversion, so the wiring in their charts matches) but I would keep the HEI module attached, and the wiring harness in the glove box. If this ever happens again, you can simply plug the wires back into the HEI module, change the wiring, and be back on the road again.

If you have a digital MSD box, that would be the first one I have heard of that is failing. l would suspect the HEI module on the distributor first, by-pass that and use the mag pickup to fire the MSD.

But before you do anything, check the big ground wire on the MSD, make sure that connection is clean and shiny.

JW

 

I had an issue with my Mallory Unilite distributor where the engine would shut off intermittently. Initially, I found that I was losing the tach signal to the ECM. I replaced my Mallory Hyfire ignition box with an MSD 6A box and retimed the engine at that time. Everything was fine for a month or so. For some reason, I was resetting the timing and as I turned the distributor, the engine died and I lost my tach signal. I rotated the distributor back, and it fired right up. It turned out to be the three wires to the module, which are only 22 gauge at best, were broken where Mallory installed a nylon clamp where the wires go through the housing. I ended up soldering the wires and heat shrunk each wire. I then twisted them and installed heat shrink over all of the wires so that it conformed to the distributor housing. I left the clamp off, reclocked the distributor so the wires didn't make a 90* turn, and used dielectric grease where they went through the housing to make it slippery. I ultimately disconnected the vacuum advance because I see no way that those small wires aren't going to break at some point. GM had some issues with pick up coil wires breaking due to the vacuum advance, but the distributor and wires to the pick up coil were larger and it usually happened after many thousands of miles. When I was trying to diagnose my issue, I eliminated the module because even with only one wire not broken, it still fired the coil. Check the wires in the distributor.

 

OK, level set here. I have an MSD-6AL of unknown vintage. I have a small-body HEI distributor that is only the hall cell pickup. It is triggering the MSD from the pickup, not the points wire. There is no HEI module in this distributor. This is what left me on the side of the road.

When I had my wife pick me up, I dug out my 100% complete and separate HEI distributor and some jumper wires as my fallback to get home with.

All I need to do is figure out if it is the A) coil, B) pickup or C) MSD box. It seems everyone in this thread has had at least one failure of them all at one time or another.

If it's the coil, that's easy and I have a spare already. I'll swap it and see what happens while not venturing far from the house.

If it's the pickup, that seems easy too but diagnosing it might be harder if it only happens when hot. I do not have a spare.

If it is the MSD box, I'm probably going to take another distributor and convert to Pertronix or something similar and ditch the extra stuff that is complicating my life.

 

exactly. The msd doesn’t care what fires it. My deal was an MSD distributor. But that doesn’t matter. Just have to have something spinning in time when using a pick-up that is in time with the rotation potion of the timing events. Kinda simple. We are over thinking this. But it’s ok. Still money on the pick-up.

 

A point’s distributor was originally designed to fire the msd….using the points

 

Better to regain your vacuum advance and SCRAP THE UNILITE.

 

That's the way I'm doing it...

If I had to guess at Greg's problem, I would say it's something with the magnetic pick-up in the distributor when it get's hot. If that is the issue, it's probably cheaper to replace that then to buy the Petronix stuff (which has given some people fits, too).

 

I tried the points distributor to fire the msd box. It would not rev smoothly near 6k and would break up over 6k. Worked great otherwise and I liked the stock look.

 

that is what I’ve been saying throughout this whole thread. 95.8 and a quarter sure.

 

In my personal vehicles, I've had 50% more problems with MSD boxes dying than with pickup coils going defective. 100% more problems with MSD boxes dying than pickup coils, if you don't count the magnet mounted permanently on the shaft of the Chevy TBI distributors as part of the pickup coil. The coil windings and leads were fine. The magnets are a high-failure item on those distributors.

So far, I've had an MSD5 and an MSD6T fail on me. I've had the one TBI distributor that needed a mainshaft/magnet. (I have needed to replace a few HEI pickup coils on customer vehicles.)

Don't forget--MSD spark boxes were so notorious that NAPCAR racers installed two of 'em. When one failed, he could run the engine off of the other box.

The failed MSD5 went back to MSD for repair, and worked flawlessly afterwards. The 6T has not been sent back, probably never will be. But maybe my attitude will improve.

 

do not doubt you one bit.
For me? Never ever had an Msd6AL bite it. Thought so. But in the end it was always something else. And again mainly a pick-up source problem.

 

I'm with Guy on this. Of the few 6AL boxes I've had, none have failed. I though one did and got a replacement, but it was the FAST electronic conversion pick-up in the distributor.