Reply to "engine wont switch off"

If the ignition continues to fire after the key is shut off, one possible cause may be voltage is continuing to be supplied to the coil and/or ignition module. However, a second possible cause is the carburetor butterflies being too far open at idle, as a result of "retarded" ignition timing at idle (6 degrees).

If both the fan & ignition circuits are modified as I've drawn the ignition and fans will not interact with one another. But, problems arise with the Pre-L cars when folks try to use existing wiring. My hope is always that folks will "strip" the wiring far enough back that problems inherent in the wiring harness are eliminated. Other modifications such as non-original alternators can impact this, as well as other wiring changes made by previous owners.

The little blue alternator idiot light does not need to be functional. The car is equipped with either an alt gage, or the alt gage has been replaced with a volt gage. Either of those gages provide more information than the little blue idiot light. Its not needed, unless you have an original style mechanical voltage regulator I would hope the blue light has been left inoperative.

Here's my check list.

(1) Time the engine as suggested (18 degrees static, vacuum advance attached to ported vacuum), or use the idle solenoid the car was originally equipped with, so the butterflies are reasonably "closed" when the key is turned off. Otherwise the engine will want to "diesel" ... i.e. continue running.

(2) An ignition power relay should isolate the ignition (coil and module) from any source of power when the key is switched off. If it doesn't ... why not? This is easy to check.

(3) The modified fan wiring I've suggested will positively isolate the fans from the car's entire wiring system when the key is turned off. They will not be capable of "back-feeding" power to anything.