bouis

For reference, my car is an '85 S (12a) with a 4-speed auotmatic and a racing beat sp exhaust.

I'm stumped on this one. In the past month, I've blown:

the trailing igniter (lasted 18 years, as far as I know)

one MSD 6al (lasted 6 days)

one more MSD 6al (lasted 6 days)

The MSDs were hooked up as follows: green and purple to distributor (yes, correctly), red and black to leading coil #1 positive and negative respectively, orange to negative on trailing coil, and large red to battery positive terminal.

The trailing igniter failed under heavy load (roughly 5.5k rpm in third). So I replaced it with a direct fire MSD setup as per the standard tutorials.

Well, the first MSD ran great. I was really impressed with it until it failed. The second one didn't idle very well from the get-go (I figured it to be the plugs, which very likely fouled during the miserable rigging to swap the trailing ignition over and get off the side of the highway; I have the receipts to prove this, as I bought new plugs but never got to try them). Neither MSD started as quickly as stock [roughly .5 seconds versus instantly] when the vehicle was hot, although they were much better for cold starting. Both had been taken beyond 5k rpm several times with no previous problems. Both were installed where the sub-zero starting assist bottle normally is.

Both failed at roughly 70 mph after downshifting from overdrive to third (this being roughly 5000 rpm) and after sustained highway driving. One with the headlights on and one without. Both were quite obviously the point of failure, as they were smoking immediately afterwords and smelled of electrical fire.

I'm not an electrician. I don't know what part of the MSDs failed. But I do have a couple theories:

1) The negative on the trailing coil is where the fuel pump relay gets its signal from. But I tested voltage here and it only seems to have juice when the ignition is firing; that is, at idle it noticibly bounces.. but maybe it's on all the time just less. I don't know.

2) The voltmeter in the car reads ~13.9 with the headlights on. This is a bit higher than my old RX-7 was, if I remember correctly.

3) I didn't install a rev limiter chip and I didn't cut the wires to set the MSD for a 4-cylinder.

4) I crimped rather than soldered my connectors (but so did MSD, so why not?).

I could send MSD #2 back to MSD; in fact, I probably will... though I probably could get it swapped out again if I have a good reason to expect that the next one won't fail.

I'm just looking for anyone's thoughts on this one. I changed the last setup over to stock from the trailing on the side of the road with nothing but a pen clip and a fuse... thank God for the rear wiper. (I don't actually have one, my car being an S model.) I don't want to go through that again.

Jeff20B

iTrader: (13)

bouis, your next MSD will fail if you don't redo your wiring.

If I were you, I'd ditch the MSD altogether and go with something else.

Wait, you said orange to negative on the trailing coil? If I remember right from over two years ago when I had a 6AL on my 13B, the orange wire should go to the leading coil. The trailing coil is on a different circuit. The black and orange wires carry the CID spark and should be sent to the leading coil only.

I'm not sure where you got your information from, but something isn't quite right here.

Now that I've been thinking about it for a few minutes, I know the thin red wire should go to the key ON switch wire which connects to the + side of the trailing coil. This wire turns the MSD's internal relay on. The leading coil must not have any other wires on it, other than the orange and black ones.

I guess it's good that I'm brushing up on this stuff because I'm going to hook a 2nd gen leading coil to my 6AL for better direct fire than with two coils.

knight1976

I just did my msd-6a last night and this was a GREAT help. http://www.mazspeed.com/msd.htm

bouis

Yeah Jeff20B, I had swapped small orange and small red in my writeup above (not on the car, but that would be hard to do, wouldn't it?)

I beleive that the problem was that I had the thin red wire on the negative side of the trailing coil (it has the right connector on it already, after all) and I was thrown off by the fact that it, well, worked for six days...

I know I had it on the negative side the second time. I also know that I had planned to put it on the positive side from the beginning, so I'm not sure about how MSD #1 was set up. I think I'm going to try connecting it to the positive connector for the leading coil on the stock harness first, since someone on Mazspeed recommended against putting it on a coil. My friends at AutoZone have promised me an unlimited supply of MSDs, so we'll see .

Jeff20B

iTrader: (13)

Oh, ok. Good luck.

bouis

Thanks for your help by the way.

bouis

Executive summary, for anyone who might be doing this in the future:

Just because the small red wire has a female connector on it that matches the C shaped terminal on the negative on the stock coils, and though it seems to work fine that way, it isn't, and it will eventually cause the MSD to fail.

1984special

Ouch. I'm sorry to hear you lost 2! MSD boxes....

Those things are expensive! And the evidence proving their effectiveness is quite unclear, on the GSL-SE motor at least.

bouis

I haven't lost any. AutoZone has . Great part is that I got the first one for $140 to boot.

As for the effectiveness of the MSD, I can testify that they work extremely well. Most noticable difference is cold starting on a cold morning. When it works, the MSD is probably the best upgrade IMHO.