Inliners International Forums General Discussion Hi Performance MSD Box

Alright guys. I installed my MSD 6A box, HEI, Blaster 2 coil, and MSD wires (along with some other things) this weekend. The whole setup is great, I couldn't be happier, except for one problem. When I turn the ignition switch off, the truck continues to run. I'm pretty sure I've got everything hooked up right. I followed MSD's own book for the wire hookups.

Purple & Green--Magnetic pickup
Small Red wire--Switched 12v
Orange & Black--Coil positive and Negative
Large Red Wire-- Bat. Positive
Large Black Wire-- Bat. Negative
White-- Not used

Now, the only problem I can think of is that the Small Red Wire has constant power. But it doesn't. It's the same wire I ran to my Pertronix setup. I unhooked it and checked, just to be sure, and it is switched. I'm at work right now, just trying to get some ideas on how to fix this. Any help is great. I'm going to go back and triple check the wiring later. Thanks. John

Update. I'm still at work, but I couldn't help it. I started up the truck, and tried to use the key to shut it off. Nothing, still running. So I unplug the switched 12V wire and the truck shuts off. Kinda wierd. I'm going to see if I can find another switched 12V source, and try that. I'm kinda stumped here. John

Would some other things include an internal regulator alternator? If so, you may have your field wire hooked to the ignition side of your switch instead of the accessory terminal. I have seen this before. It feeds back and won't shut off. Just another possibility. Joe

Hy. I have, in my 6 cyl 232 AMC engine, the MSD set up:
-Blaster II coil (45000v)
-MSD 6A box
-MSD 8.5 mm wires
-MSD Billet distributor(8516)
-Spark plugs gapped at .050

...followed the instructions and it works fine. I do not have that problem(continued motor run) but there is a section in my instructions that mentions something like that, in case of a car not turning off when the ign switch is turned off. I did not pay attention to it since it did not happen to me, but I will check into it.
I do not have a HEI system, but I think the MSD 6A box has a diode or something of that sort in the kit(instalation), for the time when what you are experiencing now happens. I think it is due to the system being capacity discharge, more potent and with it's own energy(stored in a capacitor), so the diode(SUPPLIED)has to be installed within the system according to their instructions. Check out the instructions. Also, MSD is good with technical support, I called them to verify the spk plug gap, and also with questions about my MSD distributor( finding the correct dist curve) and they are very helpfull,excelent support. The number is within your instructions.
Give them a call. I will read my instructions about the dieseling/ diode in question.

JaIME.
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Hy. To add to the MSD connection topic, I used the original wire from the ign switch to the pos side of the coil(stock wire) as the connection to the red wire to 12v source from the MSD 6A box.
As you know, with the MSD set up, the ign switch does not go to the coil no more, but to the red wire of the MSD 6A box.
It worked excelent in my car.
Jaime.
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I swapped to another switched 12v, .015v when switched off. I'm still having the same problem. I read the voltage on the wire with the ignition OFF and the truck running. I got around 8V.

Joe-- I'll check into that. I did install an internally regulated alt. I haven't had any problems with it though. I'm thinking you're onto something.

Jaime-- The diode is one of the later HEI units. I think it's a 5 pin one. It's only needed when you use that type HEI, and if you experience hesitation upon deceleration. I also used the same wire from my Pertronix setup on my MSD box.

I'll take another look, or three, at it. Thanks guys. John

Hy. About the diode, I read about it, the MSD instructions say that the problem with the engine not turning off is due to some older alternators having a separate Voltage regulator. The problem is the charging light, which sends voltage to the system(MSD box) after the ignition switch is turned off. The diode(supplied) is to be connected between the charge light circuit , the voltage regulator and the 12V wire, in a set up/diagram provided by MSD in the instructions. I am not at home, that is why I keep refering to the MSD instructions as not being around me, I do not have a PC at home, I use the library's or work PC.I must go, but I will bring the tech info, also available by calling MSD.
Later___________________________________

Jaime- I'll look in my MSD book when I get a chance. I have an internally regulated alternator, so the external regulator has been bypassed. The number 1 and 3 terminals are jumpered together and the number 2 and 4 terminals are jumpered together. I'll have to wait till tomorrow before I can look in my book. Thanks. John

On the MSD website under Tech Support / Troubleshooting they address the run-on issue. There's a diagram too.

http://www.msdignition.com/

Sounds like your are having Igntion run-on problems. Make sure your power wire that runs to the Alt. to the Ignition switch feeds through an Idiot-light. This could also be corrected as suggested by using a diode, But is not recommended as the diode creates an in line volt drop of .7 volts. In other words the 12 volts at the igntion switch becomes 11.3 at the regulator. It appears to the Alt. that the battery is low and it causes the Alt. to over-charge. Maybe this will help--Paul

Alright guys, I got the diodes. I installed an internally regulated alt. about 4 months ago, so the stock one has been bypassed. I'm just going to follow this diagram and either put it inline with the alt. or the MSD box.
http://www.msdignition.com/1troub1.htm#runon
I'll let y'all know what happens, because it's going to be a week or so before I can work on it. Thanks guys. John