I'm working on a 99 Olds 88. It has a new alternator, battery, and starter. When I turn the key I get one click. The security light comes on solid and goes off after about 5 seconds when the key is in run so I'm guessing it isn't the security system. I wish it was because now I'm lost. Battery has 12.6v, battery to starter thick constant power is 12.6, however, battery to solenoid post when key is cranked is 9.3v. I want 12.6 correct? What should I be looking for? Should I look at the ignition switch? I read that this vehicle does not have a starter relay-Is that correct?
Any advice anyone can give me would be much appreciated!!
Thanks,
Mike

Did it run before the work was done?
You say the solenoid post goes to 9.3 when cranked. Does that mean the engine turns over?
Here'* the wiring diagram of the starter circuit.

Thanks for the diagram. To clarify, it'* my neighbors car. She said it did run perfectly. She pulled into the driveway and it wouldn't start again. Her brother put a new battery in and alternator but couldn't get under the car to put in the starter. I put the starter in. When I said "when the key was cranked", I meant as if you were attempting to start it. It get'* one click and that'* all she wrote. Will not turn over. So the 9.3v is with the key turned as if you were starting it. I cranked it by hand to make sure it wasn't seized and it moved just fine.

Check the connections on the side-post battery.

Make super sure that both positive leads are connected to the positive side of the battery, and that the spacer is there. This is a nuisance trouble area on these cars.

I will do. Thanks for the heads up

I installed a new starter and solenoid. I had power to the entire car. Security light stayed on for about 5 seconds but no crank or start. After days of searching online and climbing in every crevice of the car i ended up holding my lock and unlock button on the key fob and then i turned the engine over and it started right up. Wish I knew this 7 days ago.