MSD making car run bad? random spark?
Thread Starter
Race Director
Joined: May 2003
Posts: 10,956
Likes: 409
From: California
Ok... did it all... still the same and I replace the unit also... so it must be something else... but this thread will probably help others with MSD problems... Than you everyone for your help and input. Paul:-)
Racer
Joined: Dec 2005
Posts: 368
Likes: 4
From: . New Zealand
Once built an engine for a guy with a '32 2 dr sedan with a 383 SBC and it had a MSD6AL. When it was fired it ran real rough, could not understand it. Turned out that the Auto Electrician had took it upon himself to swap the MSD power leads from the distributor in the plastic connector plug, his reason, the purple wires did not match each other! Changed it back to the MSD wiring diagram and smooth as silk.
Thread Starter
Race Director
Joined: May 2003
Posts: 10,956
Likes: 409
From: California
Once built an engine for a guy with a '32 2 dr sedan with a 383 SBC and it had a MSD6AL. When it was fired it ran real rough, could not understand it. Turned out that the Auto Electrician had took it upon himself to swap the MSD power leads from the distributor in the plastic connector plug, his reason, the purple wires did not match each other! Changed it back to the MSD wiring diagram and smooth as silk.
So, another question..... can the pick up in the distributor be bad on a specific or row of specific cylinders?,,,, It seems I always get the fraken hard ones to figure out.... so many mods...
Melting Slicks
Joined: Jul 2005
Posts: 2,060
Likes: 46
From: winter haven florida
St. Jude Donor '12
i can tell you that a digital 6 msd will cause running problems right before it goes out. i had a new digital 6 that ran great. tonight when i started the car up it was wanting to backfire through the carb quite a bit. tried to adjust the timing and it got worse, very soon after it lost all spark. i switched back to my very old 6al unit and it runs very well now. they will misfire before they break.
Burning Brakes
Joined: Dec 2007
Posts: 952
Likes: 0
i can tell you that a digital 6 msd will cause running problems right before it goes out. i had a new digital 6 that ran great. tonight when i started the car up it was wanting to backfire through the carb quite a bit. tried to adjust the timing and it got worse, very soon after it lost all spark. i switched back to my very old 6al unit and it runs very well now. they will misfire before they break.
Yep. NASCAR runs two. They benefit from them. These cars they are really unnecessary.
Burning Brakes
Joined: Apr 2007
Posts: 1,028
Likes: 1
From: SOUTH ELGIN IL
Don't have time to read all the posts right now but my MSD 6AL box went bad last year and the car ran very rough and I couldn't rev above 3,000. Felt like i was dropping cylinders all over the place and they told me the same thing and that it was probably the fuel system.
Long story short, I sent the box down to MSD in TX and $80 later no more problems. I had bad capacitors, bad resistors, the whole nine yards in there.
My car still ran with the bad box, just like sh*t. good luck.
Long story short, I sent the box down to MSD in TX and $80 later no more problems. I had bad capacitors, bad resistors, the whole nine yards in there.
My car still ran with the bad box, just like sh*t. good luck.
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
I have had MSDs for ~25 years - great system! However, I had a friend who had problems because he had inadvertently hooked up the magnetic pickup wires backwards. If this is done incorrectly, the spark occurs erratically approximately midway between when the points of the rotor pass the points of the stator (HEI), or the arms of the rotor pass the pickup coil.
This problem is easy to troubleshoot...
1. Pull the distributor out about half way and remove the rotor so you can see the points on the star wheel (or arms on the rotor).
2. Arrange the high voltage wire from the coil so that it is approximately 1/4 inch from any ground.
3. Turn on the ignition system
4. Turn the distributor shaft by hand and check that the spark occurs when the points on the rotor pass those of the stator (HEI), or when the arms of the rotor pass the magnetic pickup coil. If the spark doesn't fire at this instant, reverse the pickup wires and test again.
This problem is easy to troubleshoot...
1. Pull the distributor out about half way and remove the rotor so you can see the points on the star wheel (or arms on the rotor).
2. Arrange the high voltage wire from the coil so that it is approximately 1/4 inch from any ground.
3. Turn on the ignition system
4. Turn the distributor shaft by hand and check that the spark occurs when the points on the rotor pass those of the stator (HEI), or when the arms of the rotor pass the magnetic pickup coil. If the spark doesn't fire at this instant, reverse the pickup wires and test again.
