Possible MSD 6AL failure

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oldskool

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My 68 Cuda's using an MSD 6AL (6420, the analog one). A few weeks back, the car stalled out and would not crank over. It was a hot day but I hadn't been driving long. I had it towed to my mech and he confirmed that the spark was igniting so that wasn't an issue. By the time the car was at the garage, the car had somewhat cooled so other than a flooded carb, it did start. He warned me that sometimes the MSD can get hot so it may need to get cooled if the contacts start to separate, one of the reasons he stopped using MSD. He had the car for a day and didn't notice any other issues.

So last night I started the car fine. The car idled low and turned off, which I left to me not letting it warm up enough. I'll note that the carb's been tuned as recently as last week, so I don't think it's a carb issue. I tried to start it and it did the same thing as before and it wouldn't crank. After a few minutes to trying, it finally started and made my way gingerly home.

I'll add that the engine seems to run smooth, so I don't feel any misfiring.

This problem seems to be 6AL related as I've read similar issues like this. I've got a couple of questions.

1) Does it seem like a 6AL problem? If not, what else would I be looking at.
2) If it's a 6AL issue, I assume the only solution is replace the box?
3) Is the 6420 directly replaceable with the 6425? I'm hoping I can just swap boxes w/o having to mess too much w/ the wiring.
4) Since I'm already doing this, is there any danger to me using spade connectors on the wiring? My mech has a few boxes and it'd be good to have ones to swap out.
5) What's an alternate to the MSD solution?

Thanks in advance. This board has been a WEALTH of info, especially compared to other A body forums I've been on.
 
Where is it mounted? The thing should be away from engine heat

Could be a coil starting to fail. This is classic coil failure, IE fail when hot, work when cold.

Might not be ignition at all but something else.

You need to acquire some troubleshooting skills. Learn to check the spark when cranking. Get tools that allow you to do this "alone." You can buy spark testers.

Understand and acquire knowledge about "how it works."

EG:

Mopar ignition switches have TWO ignition voltage supplies, one for "run" and one for "start."

Let's say the "start" circuit has a problem and you don't have voltage to ignition for start. YOU MUST check this by using the key to start.

If you check spark with the key in run, and by jumpering the starter relay, you will mask the problem, because you changed the conditions of the problem.
 
The 6AL is mounted on the driver side fender, away from the block. The coil? Good question, I'll have to check that.

Thanks for the pointers, I'm all for being self sufficient. I'll look into those suggestions.

Fortunately, MSD had something I can use to check the ignition. Mine's magnetic, the white wire is attached to a kill switch. Come to think of it, the problem pretty much acts like the kill switch is on.

http://www.msdignition.com/page.aspx?id=3206

As far as the hot/cold, I would've considered heat being the issue with the 1st occurrence. However, last night I started the car after it had sat outside for a few hours, so no chance that the car or MSD was hot. It's a bit of an intermittent issue, making it more frustrating to debug.
 
I would disconnect the kill switch. If the switch or the wiring has some moisture / condensation problems, (EG) it might have some "leakage" current.

I guess you have read? The destructions at MSD. There are some troubleshooting procedures there

What is it? exactly that you use for a distributor?

You may be able to inexpensively "rig" and emergency ignition. I use a 4 pin HEI module in my car, and built a box to fire up used engines. THEN it occured that it serves as an in -trunk emergency igntion:

Here's the wiring. Important to note the drawing of the Mopar distributor connector. If you use "other than" a Mopar distributor, you may need to reverse them to get proper rotor phase



My emergency system. This is a factory Mopar coil I had, with an HEI inside. Yellow hooks to battery, green is ground, and of course plug wire and the distributor connector




If you use one of these, you need to provide a certain amount of heat sink for the HEI. They have a projection on the bottom, you either need to break it off, or drill a clearance hole in your mount. Mine in the car is screwed directly to the firewall, this one of course is an aluminum box
 
You say the car "wouldn't crank" which normally means the starter motor was not able to turn or crank the motor over and would be a starter/relay, or bad battery terminal problem.

When you had your issue could you elaborate? Was the engine turning over but not starting, or was it not turning over at all?

I personally have not seen an msd box quit due to heat and then start working again. When I have seen them go bad they were finished. Perhaps seone else can chime in?
 
Mine went out in my truck one day no spark at all . Had my truck carried home checked everthing determined it was my MSD box sent it back to get it checked. In the meantime I bought me a new one put it on and it fired right up. Then they sent my old one back said nothing was wrong with it. Who knows. I changed coils before I changed MSD boxes that didn't help. Its running now and ive got a extra box. I think once their gone their gone.
 
If you do end up having to send your MSD box out to get looked at or fixed, call Pat at Techwest racing. He's a guru with MSD boxes and will even upgrade the internals so you'll have a hotter box than when it left MSD's factory.
 
MSD: May Suddenly Die

Its only a matter of time. After 2nd 6 died , i went back to a 40 year old Mallory hi-fire V and it hasnt given me any trouble.....take the 6 apart (drill the rivets out the bottom) it looks like a hand soldered 1950 Zenith TV.
 
if you are running a mopar electronic distributor...check the pick up coil air gap....the msd is sensitive to that air gap...

should be .008 with brass feeler gauge.
 
All great input, keep it coming. Awesome referral on Techwest, I'll try their test as well.

http://techwest.ipower.com/page2.html

I like the idea of Techwest looking at it, I suppose MSD can 'fix' it, but if someone knows how to make it bulletproof, even better. I've considered replacing it but the more I dig, the more I hear about 'issues', granted many others have no issues.

I opened a can of worms, you guys all gave me homework this week after work. ;)

I doubt it's the kill switch, I installed it this weekend but the 1st issue happened before it was even installed. BUT, I'm not discounting anything at this point.

As far as the distributor, I don't recall what it is, I'll have to check later.

Yeah, it's intermittent, so it's hard to narrow down. I wonder if if the car's running fine if I'll even see the issue on the 6AL or coil at all.

I'll clarify my prev statement. When turning the ignition on, the engine will turn over but it doesn't start at all. Last night I got 'lucky' that it finally did start, but I'm not relying on that anymore.

My mech gave me one of his old 6400's and I'll also try to swap that in so I can have a running car. While the 6420 is out, I'm going to open it up and see if there's any cold solder joints or blown transistors. I'm a EE, I can look at it from that standpoint and see if anything's obvious. I really hate the idea of just swapping 6ALs, just waiting for another to die an just replace. At that point, I'd rather have a more reliable solution.

BTW, I've also confirmed that my 6AL is not one of the counterfeits.
 
I had this issue .. as stated above make sure you have .008 reluctor to pickup gap.
 
Crap, I may have a more basic problem.

My MSD ignition consists of

- 6AL Model 6420. Older analog one before the current 6425
- MSD distributor cap. Not sure of model number, didn't want to pull it.
- Blaster 2 coil. MOUNTED HORIZONTALLY.

I remember reading some threads that this coil is oil cooled and needs to be mounted horizontally. Looks like I'm off to buy a Blaster SS since my mounting locations are limited. Any one have experience w/ an Blaster SS? I'm hoping it's just a drop in replacement. I'm going to check the MSD forums but it takes FOREVER for their admin to approve me.

I'm still checking the resistances on everything just the same as a sanity check.
 
I been running a blaster 2 coil horizontally for 20 yrs....
 
Made some measurements, no engine firing though. Garage too close to the house and the car's not exactly quiet. Doesn't make for easy night time wrenching.

1) Per Techwest's test (http://techwest.ipower.com/page2.html) I'm getting way above the 3K, so nothing obvious there.

2) Per MSD (http://www.msdperformance.com/page.aspx?id=3304), on the distributor I'm getting about 600 ohms.

I didn't get a chance to measure the coil, I'll do that tomorrow.
 
I'm a EE, I can look at it from that standpoint and see if anything's obvious.

Grab the bull by horns! A clamp-on timing light uses a current transformer, so it needs spark current to trigger. While the blink may be enough, there is more information. I have added BNC connector to a cheap light, and use a scope. The internal circuit provided enough burden resistance for measurement.

Spark testers also work. There is little reason to ponder, use simple tools, to get definitive results.
 
Any spark testers you guys recommend? I see a ton on Amazon, some w/ just on/off light, some w/ adjustable gap, etc. Might as well do it right the 1st time and make sure I have the proper tool, as I'm probably going to be using this a lot.
 
Spark tester I have seen are often cheaply made. If you spend $25, you can get a 2KV, scope probe to look at coil primary signal. From that, you can estimate secondary voltage, and measure duration.
 
If you find your problem, remember to post it here and how you fixed it. I have the exact same problem. Car starts then quits. Look under hood, find no obvious problem and then try key again. Sometimes it will fire right up again, sometimes it takes a few tries. This will happen a few times then the car will run perfect for a couple of hours. Frustrating as hell not being able to track down an intermittent problem.

Jack
 
Spark tester I have seen are often cheaply made. If you spend $25, you can get a 2KV, scope probe to look at coil primary signal. From that, you can estimate secondary voltage, and measure duration.

Ah yes. But that assumes I have an oscope, which I don't at home. Sadly, I don't have a full on bench at home garage. That's on my wish list.
 
Rig up a spark plug, by by connecting a female plug end on the ground. Lay it on insulating mat, place in series where you can see it.
 
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