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View Full Version : MSD 6AL and 5-pin GM HEI module...


Steady Freddie
03-20-2010, 09:43 PM
Not sure if my box is dying or sick, (I wish I knew what the signs of a dying MSD 6AL are).

For other reasons I decided to retro to a vac advance HEI system with a 5-pin module and it was'nt happy with the MSD box, (stalling and timing issues).
It stalled at differant speeds when I acellerated and darn near died a few times. I disconnected the box and my car ran fine. :001_huh:

I bought this box back in 2004 from Summit and I installed it on my computer controlled HEI/CCC system with the 7 pin module. Although she ran good I could never get the tach to work right even with all the MSD adapter stuff I bought and installed. :angry::cursing:

So what exactly is it? Is it the diode issue or a sick box? (What is the diode I need in case I decide to test the box again and eliminate the diode issue as a possible problem on the 5-pinner)? :confused1:

bill jones
03-21-2010, 10:21 AM
-I can't remember for sure but I think if you are trying to run a 4 or 5 pin module and trigger the MSD box with a white wire you'll likely have problems particularly below about 3000 rpm.

-seems like I tested the Hei's with white wire trigger and eventually found out that the HEI module changes dwell between idle and about 3000 rpm---and the MSD is switching up from many sparks at idle speed to 3 sparks between 1100 and 2200, then up to two sparks between 2200rpm to 3300 and then again at about 3300 to a single spark--sort of like shifting gears.

-I think the dwell changing of the HEi module and the multispark switching of the MSD confuse each other and create the problem.

-the 5pin module also has the knock sensor spark retard system that could be interfering with the signal that the MSD is seeing.
-----------------------------------------------------------------------
-If you eliminate the HEI module and use the 2 magnetic trigger wires to run the MSD box the problems you mentioned should be 100% eliminated.

-We have run HEI's magnetically triggering MSD6's for years and never had any issues.

Steady Freddie
03-21-2010, 05:43 PM
Not sure if I am understanding you. But I tried that, won't start. I installed it like the MSD instructions showed for a 4-Pin module....which is magnetic pick-up triggerering.

I've tried it several times and it won't start. So I've had to wire it up for a HEI 5/7-pin module. Starts up but with all the problems I mentioned above.:crying:

bill jones
03-21-2010, 08:49 PM
-the MSD tech guys will get you all straightened out tomorrow.

msdtech1955
03-22-2010, 10:25 AM
is this a carb or fuel injection application ?

Steady Freddie
03-22-2010, 01:00 PM
Carburated.....

I think I may have installed according to the magnetic pick-up triggering instructions but forgot to disconnect the white triggering wire from the brown wire of the HEI. Will that cause a no-start condition?

msdtech1955
03-22-2010, 02:07 PM
yes....it needs to be connected like this.

1181

Steady Freddie
03-22-2010, 07:05 PM
I don't have an external coil, (will the orange and black wires from the MSD box go to B+ and C- on the HEI distributor coil)?:001_wub:

And the HEI ground to engine ground while white trigger wire from MSD box gets black taped?

msdtech1955
03-23-2010, 09:50 AM
just hook the orange to b plus on your cap and black on the coil negative.

and on the white lead...you can cover it with tape or heat shrink..

Steady Freddie
03-24-2010, 11:22 AM
Well it works, (magnetic trigger). It has a smooth idle and a quick start but....I'm back to my original problem. It stumbles at different speeds when I accelerate.

I can rule everything else out since I swapped out three working different coils, (1-brand new), and it still does the same thing. Lastly, I'm going to do an ohms test on the pick-up coil since that's the only other thing that may be faulty, (I'm not optimistic though. The ignition system does not stumble when I disconnect the MSD box). :crying:

msdtech1955
03-24-2010, 12:40 PM
are you still using the vacuum advance ? if so..unplug it ...and drivr the car with just mechanical advance.

Steady Freddie
03-24-2010, 01:04 PM
Way ahead of you...yes it has vac advance. Yes disconnected to make sure it's not vac related drove it around. No differance...

msdtech1955
03-24-2010, 03:08 PM
when you check the timing...does it advance right away ..>

Steady Freddie
03-24-2010, 06:39 PM
Darn...:001_huh:

It slipped my mind. I had already disconnected the MSD box by the time I got your reply. I did have the distributor vac hose on the wrong carb port so it probably was'nt getting any timing anyway when I had the MSD connected.

Don't know if that would cause the stumble, but I tested the MSD box with the distributor canister connected and disconnected and the stumble continued.

I ran a little test with my vac pump on the distributor canister and timing light and it is pulling timing. I did several runs on the highway without any problems what-so-ever, (but this is without the MSD box).

I will try it next with the MSD box.....but I am not hopeful...:sad:

msdtech22
03-25-2010, 11:21 AM
We have a diode fix for the 5 pin diode that will cure your hesitation problem.

We can send you that piece or by using the drawing in this attachment, you can apply it your self by using the parts illustrated.

Steady Freddie
03-25-2010, 01:02 PM
I'm good with that diode fix for the 5-pin. But I was really digging the simplicity of the magnetic trigger set-up. What next to troubleshoot? Should I give up and just go for the 5-pin diode fix?:confused1:

What could cause the stumble? :crying:

msdtech22
03-26-2010, 11:13 AM
Try the diode fix.

Steady Freddie
03-27-2010, 06:45 AM
OK...but it will have to wait some. I'll bring back this thread when I do. For now I'll have to drop off of the rader. Too many projects and so little time. I'll see you at a later date. :001_cool:

msdtech22
03-29-2010, 07:11 AM
Let us know what happens after you try it.

OldMech
06-07-2010, 10:01 AM
This was the reply that I needed to fix my problem TWO DAYS AGO! I looked and searched trying to figure out where to put the diode, I finally gave up, pulled a 4 pin module dist from my shelf, rebuilt it, and rewired the 6AL for it, and it works OK now. I think.. next time i buy a product that I MAY need help with that I will try to fond someone that actually HAS tech support on the weekend...
You know the weekend? the two days between Friday and Monday? Those two days where someone who buys an MSD product might have the necessary time to install it? Those two days out of 7 when they arent working 14 hours a day to support their family? Yes, i know working weekends SUCKS, I do not want to work on the weekends either.. however, the weekends are the onoy time I have.. my first run is sat morning.. so i had THIS weekend to get the prob fixed... period.. If I hadnt found the 4 pin Dizzy I would have sent the 6AL back accompanied with a VERY unhappy note.. as it is I am not very unhappy, justy mildly annoyed..
i have used 4 6AL's over the course of time and have been very happy with every application i used them in... until this one...
I registered for this Forum the same time i sent my questions to Tech support.. I tried calling as well... but was told by a recording they were closed... so Even just a forum administrator that checked applications between movies, Doughnuts or whatever would have been TREMENDOUSLY helpfull... but, like tech support.... I had to wait for monday.. when i no longer had the time to deal with the problem.... Hmm, come to think of it.. I still have no answer from tech support... Very proffessional huh?
Can you feel the love? :001_wub:

msdtech1955
06-07-2010, 10:09 AM
well unfortunately, we do not work on weekends answering the phone.. most of us are attending races,car and trade shows,even tractor pulling events across this country ..so , sorry for the delay ...... if you still need our help...please p/m me a phone number and time to call.:001_cool:

Steady Freddie
06-07-2010, 11:11 AM
LOL!!....:thumbup:

Been there. Frustration makes people unhappy, (a lot of emotion in that posting). MSD products are still good though.

msdtech1955
06-07-2010, 03:24 PM
thanks , for the thumbs up.

OldMech
06-16-2010, 01:25 AM
well unfortunately, we do not work on weekends answering the phone.. most of us are attending races,car and trade shows,even tractor pulling events across this country ..so , sorry for the delay ...... if you still need our help...please p/m me a phone number and time to call.:001_cool:

yah well i still have no answer, I agree the product is good or i wouldnt use it, I just hate unprofessional tech support. being the best (most skilled) tech support in the world wont help someone if you never reply to them.
Again, I like the product, just don't like the time it takes to get a reply. :cursing:
THE box is working very well with the 4 pin module. We had a run saturday, and came in 4th in the open class, and that was against some big money :thumbup: Will see how the run this coming weekend goes. Thank you for replying at least on here 1955.

Steady Freddie
06-16-2010, 09:42 AM
OK...but it will have to wait some. I'll bring back this thread when I do. For now I'll have to drop off of the rader. Too many projects and so little time. I'll see you at a later date. :001_cool:


I still have'nt gone back to this issue but there is an update to my situation. The stumble and dying had to of been caused by an intake leak. My problem child is old carbed turbo. The turbo compessor that is attached to the intake was leaking. A bolt that attaches the compressor to the intake had stripped the threads on the intake manifold. A little soapy water revealed the leak to me. After I repaired this leak the stumbling stopped.

Steady Freddie
12-25-2012, 12:42 PM
yes....it needs to be connected like this.

1181

Can this pic be re-posted. I am revisiting this issue...(I know it's been a long time but...I love my cars).:thumbup:

bill jones
12-25-2012, 06:12 PM
-here it is----doesn't allow you to run a 4 or 5 pin---requires that you use the magnetic trigger wires.

Steady Freddie
12-26-2012, 06:53 AM
Thanks!:001_cool:

Steady Freddie
01-15-2013, 02:17 PM
Works great!

Schurkey
01-25-2013, 06:10 PM
We have a diode fix for the 5 pin diode that will cure your hesitation problem.

We can send you that piece or by using the drawing in this attachment, you can apply it your self by using the parts illustrated.
Curious: GM has (at least) two different 5-pin HEI modules, and three 5-pin wiring/electronics systems--HEI-Electronic Module Retard, HEI-Electronic Spark Selection, and HEI-Electronic Spark Control.

One module retards timing when the fifth pin is grounded; one module retards timing when the fifth pin gets a positive voltage signal.

Does the diode work with BOTH styles of 5-pin module? If not, WHICH module is this diode mod intended to be used with?



Secondarily, IF (big IF) the MSD box is connected to the distributor via the magnetic pickup, WHAT DIFFERENCE does it make what module is installed? The magnetic pickup wiring bypasses the module. The module is not even in the circuit. Therefore, no diode modification needed on the fifth pin.

msdtech1955
01-28-2013, 08:00 AM
Does the diode work with BOTH styles of 5-pin module? If not, WHICH module is this diode mod intended to be used with?

yes ..its for the 5 and 7 pin modules ..when used triggering the c.d. ignition
via' the white wire.

for cars/trucks still using the gm oem fuel ignition .( tune port- throttle body..etc.)