I'm working on a 1993 Olds 88. Got dash lights, and power to everything.
Car will not start. No power to starter. I can jump the starter at the solenoid and get it to start.

I think (not confident) I've narrowed it down to a larger connection under the dash. I have power coming into the steering column(red wire) up to the ignition switch. I have power coming back out of the ignition switch (yellow wire) when I turn the key to start. I don't have power on the yellow wire under the hood. The only thing I can find between the ignition switch and the connection under the hood, is a connection of several wires including the yellow wire, through a large plug under the drivers side dash behind the fuse box. Just before it goes through the firewall. It is a larger white or off white plug/connection just above where your left foot would be while driving. Is it possible that this plug is bad?

Joe

From what I understand, there are 2 systems the start signal has to pass through before it gets to the solenoid, the anti theft system and the neutral safety switch on the transmission.

The security system will interrupt the starter trigger, and will disable the fuel pump. Given the car starts and runs when jumping the starter, that has me believing this is not the issue (also, if it was the issue, the security light would be on steady or blinking continuously when trying to start). The only other symptom is the neutral safety switch on the transmission. Failures of these units are few and far between, but not unheard of. I have never heard of the plug you mention failing. If you put power to the other side of the plug on the starter trigger wire, and it starts up, you may be on to something.

Also, 19 years is a long time for plenty of corrosion to wreak havoc on cars, especially if there is a leak at the firewall where the windshield runs off, or a leak from the sunroof drains.

I put power from the yellow wire coming out of the steering wheel(I believe this is the ignition wire) and ran it directly to the starter. Car would turn over and try to start but wouldn't.
I then ran this wire from same spot under steering column out the window and under the hood to what I thought was the same yellow wire under the hood. No go. Back to square one. No power to starter.

I can hear the fuel pump kick in and yes the security light is flashing what I try to start it.

Am I wrong to assume that this yellow wire under the hood is the same as the one under the dash? They are both 10 guage and it is the only 10 guage yellow wire coming through the fire wall.

I am now looking for the starter safety switch and the starter enable relay. Don't even know where to begin to look. Am I headed in the right direction?

If your security light is flashing while trying to start it, then its a VATS issue.

I don't know the exact specifics for VATS across the different platforms, but on my old 95 Bonneville, you could crank the engine all day, but the fuel pump won't work. 96 and later, everything will work except for starter relay, which is commanded by the PCM.

So, now we need to determine why your VATS is disabling the starter relay.

If the security light is continuously flashing, than you have an anti theft issue. Best bet is to bypass the antitheft system.

It should blink about 5 times and then go out.

Where do I start?

Start with your ignition key. Clean both sides of the resistor pellet with an eraser.

Done that. Ready for more.

You seem to be pretty good with wire chasing. Do you think you could remove the 2 little wires from the ignition switch and maybe using a spare key, jury rig something up so you bypass the little connectors inside the switch. As already mentioned, 19 years, and that ignition switch is getting worn probably.

As a test anyway?

Do I want to use the orange wire coming out of steering column with the two white wires inside. Saw something on line where I can wire in some resistors to match the resistance between the key pellets.

Am I barking up the right tree?