Retard with an lencodrive

If you ran a crank trigger with the Promag and had timers and the Six Shooter then an unshielded crank trigger cable can cause random firing through EMI. It is NOT the 8973 that is prone to EMI, it is the unshielded crank trigger cable acting as a antenna picking up the EMI and triggering whatever ignition system is being used. This is why we had the problems with crank triggers and the 7AL2, and 7AL3 ignition systems and they are totally analog ignition systems. We burned up several nitrous motors because of this problem with a 7AL2 and a crank trigger. We kept on sending the ignition boxes back to MSD and they would tell us there was nothing wrong with the box. We would think that the retards were not working when the nitrous stages turned on. I do fault MSD in that they came out with the shielded crank trigger cable and never told us or any other racer. MSD continued to sell crank trigger sets with the unshielded cables. It wasn't until I started to talk to the MSD back room experts that I found out why we were having the problem.

 

Leahy

I assume the Leahy trigger is shielded since it is the standard trigger in the alcohol ranks.

 

It is as is the MSD trigger. The problem arises on either if you put an extension crank trigger cable from the sensor to the 8973 or the Electric Points box. It is imperative that in this case one uses a SHIELDED crank trigger cable and that the shield is grounded to the frame so that EMI is sent to chassis ground. Most of the time the Points Box is right next to the mag and close to the crank trigger so no extension cable is needed but a lot of times the 8973 is placed further back or in the case of a door car inside so a extension crank trigger cable is required.