Engine won't shut off

MtnCobra · #1 (**permalink**) 09-25-2002, 09:38 AM

Hey guys,
I'm a new member and I need your help. I am having trouble with a rebuild project, I have a Classic Cobra with a 390. The engine rebuild went well. I have a Painless wiring harness, Battery shut-off switch and MSD 6A ignition systen. The engine starts great and appears to run ok but when I turn the key off, the beast keeps on running. Any ideas where I might have miswiried something? Any ideas would be appreciated. Really great web site! MtnCobra

rphubbard · #2 (**permalink**) 09-25-2002, 10:32 AM

You have to put a diode in one of the wires for the voltage regulator. It is shown in the MSD manual.

ENGINE RUN-ON
If your engine continues to run even when the ignition is turned Off you are experiencing engine Run-On. This usually only occurs on older vehicles with an external voltage regulator. Because the MSD receives power directly from the battery, it does not require much current to keep the unit energized. If you are experiencing run-on, it is due to a small amount of voltage going through the charging lamp indicator and feeding the small Red wire even if
the key is turned off. Early Ford and GM: To solve the Run-On problem, a Diode is supplied with the MSD in the parts bag. By installing this Diode in-line of the wire that goes to the Charging indicator, the voltage is kept from entering the MSD. Figure 6 shows the proper installation for early Ford and GM vehicles.
Note

iodes are used to allow voltage to flow only one way. Make sure the Diode is installed facing the proper direction (as shown in Figure 6).
Ford: Install the Diode inline to the wire going to the #1 terminal.
GM: Install the Diode in-line to the wire going to terminal #4.
Figure 5 Wiring the Dual Ballast Resistor

Hope this helps

Maury Novak · #3 (**permalink**) 09-25-2002, 10:33 AM

MtnCobra,

Trace the thin RED wire from the MSD ignition box. It is to be hooked up to switched power. If it is always hot, the engine will continue to run.

The thick RED wire goes to the battery.

Hope that does it.

Maury

cs69er · #4 (**permalink**) 09-29-2002, 12:10 PM

thanks guys for the advice, the solution worked like a charm. mtncobra

cobrakit66 · #5 (**permalink**) 09-29-2002, 01:23 PM

just checking

G.R. · #6 (**permalink**) 09-29-2002, 02:21 PM

Cs69er or MtnCobra,

If you're from Loveland you ever run your beast up/down Big T yet? Always loved that canyon--when there weren't any "tourii"
Originally from "smell town" east of you--

Anyway greetings from a former "native" CO boy!