Cadillac Repair: caddy problem, neutral safety switch, volt ohmmeter

Question
I have a 1990 cadillac Deville 4.5 liter v8 when i turn the key it all the power comes on but nothing happens no noises or anything.Sometimes if i take off the battery terminal and then put it back on it starts. Then sometimes the battery itself is dead,and other times it just starts right up.

Answer
Hi Lee,

      You have several systems that work together to allow the engine to start. Because of the age and miles on the car anyone of them is suspect. So this is an easy way to understand what has to happen in order for the engine to start.

      First off the battery needs to be charged up...12volts or more is good...and the battery cables at each end need to be clean and tight. Blueish green corrosion at eithor battery cable needs to be cleaned off.

      When the key is turned the resistor pellet in the key is read by the PASSKEY module. When it sees the correct resistance battery voltage flows from the battery through the ignition switch, through the starter enable relay, through the neutral safety switch and over to the starter solenoid. So using a digital volt/ohmmeter or 12 volt test light and  wiring diagram you would need to trace the circuits to see where the problem is.

       Most times what I see are the wire coming from the ignition lock cylinder breaks and the resistor pellet doesn't get read all the time and after awhile not at all. Or the starter enable relay which is behind the glovebox area fails and doesn't allow the engine to turn over.

       A couple quick tests that might help when the engine doesn't make a sound would be to try the other ignition key that you have or clean that key resistor with some rubbing alcohol or peroxide and see if it might clean up and start. Also try starting the engine with the shifter in neutral with your foot on the brake or hold the key in the start position and move the shifter from P to OD and if the neutral safety switch is out of adjustment it will start somewhere in between gears.

       Try those things and see where it leads you otherwise have it towed or drive it to your mechanic when you get it to start and they can do a diagnostic because you could have a bad battery or current draw as well as a bad ignition lock cylinder an they can pin point what needs to be fixed. Hope that helps. Bill