engine and drivetrain Weird Engine Run-On

[Dev02]

Having a very weird issue going on, and I did an extensive search but can't seem to find an exact match to this.

 

4 weeks after installing an MSD 6 box I now have INTERMITTENT engine run-on. Originally everything was good, then a week or two into the MSD the engine would run for a split second after the key was turned off, and now will continue to run at times after the key is all the way out, or just shut off as it should.

 

I know the MSD can cause run-on but my reading suggests this would be an immediate thing and would happen consistently. As soon as I have the chance I will be adding the diode (capacitor? Resistor? Thingy?) that comes with the box to fix run-on; but thought I would see if anyone else has run into this.

 

Is this how run-on normally happens and will be fixed with the diode? Is something else going on and I'm killing something in my system?

 

Along with the diode I will be installing a tach adapter to get my tach back and changing out the coil to a Blaster 2.

 

Thanks in advance for any help!

[Preyupy]

Do you have an electric fan? It could also be from your heater fan. If you have it wired so the fan is controlled by the ignition switch and the fan is running when you turn the key off the fan will act like a generator until it stops and will produce just enough voltage to keep the MSD energized. If you run the fan through a relay or have a diode in the line you can stop this.

[Dev02]

No, I have the manual orange fan. I did see the post about the electric fan being a possability and should have mentioned my setup.

[mikesmith]

Definitely make sure you have a diode in the blue wire to the alternator - I believe that's the one that comes with the MSD box.

[Dev02]

Definitely make sure you have a diode in the blue wire to the alternator - I believe that's the one that comes with the MSD box.

 

Will do, thanks. Just seems weird; I drove it yesterday and it turned off no problem.