My 78' 450 only runs when the key is held in the start position, when the key is released the car dies. Any help, anybody. Thanks, tex

Not even sure the '78 450(???) has a dropping resistor, but if it does, a bad resistor will cause this trouble. Would need to check the wiring diagram. Many coils in various cars are meant to run on 8 volts, so there is a resistor in the hot lead to the coil. The start position on the switch shorts out the resistor so the coil gets 12 volts for hotter spark & better starting. If the resistor is OK, then the switch may be bad, and not supplying power to the coil when it is in the run position. The symptoms reminded me of troubles I have had in the past. This may not apply, but you should be able to check with a test light or a voltmeter and a friend to turn the switch, to see if the coil is getting power in both switch positions. Hope this helps.
John O'Shea


"Never look back. Something might be gaining on you."
"Satchel" Paige (Page?) Ace negro league & major league pitcher.

Thanks for the reply, I'll try any suggestions first before replacing the ignition switch. It is a 450sl. Thanks again, tex