My 1990 cadillac sedan deville has an ignition problem. Sometimes when I go to start it nothing happens. Turn key nothing, no click no nothing. Let it sit awhile and try again and it will start. Most of the time it will start first try. Put in a new starter problem still there. Ignition key has a security chip which I had checked and it was ok. stumped!!

The key won't turn in the ignition switch? Or when the key is turned nothing happens?

1990 Cadillac Deville, and you want the crank position sensor, The 1990 cadillac used a distributor with a ignition module, It also used a coil pick up, if you have no spark trouble shool the distributor

You can bypass the antitheft system, this will be easier and ALOT more permanent. After bypassing, this will never happen again and you dont need to worry about the airbag. PS. Airbag wires are bright yellow on GM.

This page will help you alot. Comment back if you have any questions.

http://vatspasslockpasskeysecurityhelp.yolasite.com/

Hello! There are several components that can cause no power to the starter...Lets eliminate...#1...Do you hear a "click" when you turn the key? It is the Starter Enable Relay...Powered by fuse #17 (15A)...The relay is enabled by the Pass Key Decoder Module...
Anti-Theft device...If no click is heard; The fuse is blown, the relay is bad, or the key you are using has a bad chip...#2...If you hear a "click"...The Park/Neutral switch is open/defective...#3...The power cable connection to the starter has a poor connection...

Guru..............Saailer

I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

Hard to tell sounds like the starter.

First, I would determine it is bad. I have a 1990 Cadillac Sedan Deville, and sometimes it doesn't turn over. But, if I toggle the switch a few times or up to 5 times, it starts to turn over and the car starts.

I have the same problem with a 1997 Cadillac Deville.

If you are set on changing it, here is a picture and instructions on how to test:
Starter TESTING Voltage Drop Test Fig. 1: Schematic of a voltage drop test
NOTE: The battery must be in good condition and fully charged prior to performing this test.

1. Disable the ignition system by unplugging the coil pack. Verify that the vehicle will not start.
2. Connect a voltmeter between the positive terminal of the battery and the starter B+ circuit.
3. Turn the ignition key to the START position and note the voltage on the meter.
4. If voltage reads 0.5 volts or more, there is high resistance in the starter cables or the cable ground, repair as necessary. If the voltage reading is ok proceed to the next step.
5. Connect a voltmeter between the positive terminal of the battery and the starter M circuit.
6. Turn the ignition key to the START position and note the voltage on the meter.
7. If voltage reads 0.5 volts or more, there is high resistance in the starter. Repair or replace the starter as necessary. NOTE: Many automotive parts stores have starter bench testers available for use by customers. A starter bench test is the most definitive way to determine the condition of your starter.
   

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Remember to disconnect the battery and remove the wires from the starter at the hex nut.

Then, remove the 3 or so bolts that hold the starter on using an extension and ratchet if necessary.

Hope this helps.

lower left side on driver's side near the hood release.

I fought with this issue on my wife's car for almost a year, thinking, ignition, security, starter, changing fobs, etc. I finally caved and replaced the starter - that was it.

When this happens and you turn on the ignition, do the gauges come on,etc? This will help eliminate the ignition switch/circuits as a possible cause.

Try cleaning the key "chip" resistor and if this doesn't work try the other key.

get new key with newer chip or replace ignition cylinder.