Ok so ive been trying to figure out what in the heck is wrong with my 89 gta 350 tpi for a few days now and im about to pull my hair out. When you turn the key forward it cranks over oil pressure builds but it doesnt start the lights, check engine,ect dont come on when the key is forward? just the seat belt and security light come on temporarily when you try to check codes by putting a jumper in the diagnostic port it does nothing at all. There is no fuel pressure but when you jump the top right terminal on the diagnostic port the fuel pump engages and pressurizes the rail but still no sign of starting it is getting spark however it seems the injectors arent fireing i just replaced the ecm about 2 months ago but a shop purchased it from a town 2 hours away so i dont want to try and exchange it if its not the problem. when it initially went out i believe i still had lights on the dash with key forward. any suggestions on what to do with this would be extremely helpfull. could this be a fusable link for the ecm if so where is it located all fuses in the fuse box are good. could this be an ignition coil or module or maybe simpler a shorted wire in the ignition my steering column is a little loose. whatever the problem is its not engaging the fuel pump or injectors but it does spark and crank over.

 

I don't have an 89 schematic, only a 90' but from what I see, there is a fusible link that is power to the instrument panel that also feeds the inline fuel pump relay AND the oil switch.
That may be the source of your problem.
Unfortunately I believe its on the starter.
Before you climb under, check to see if there is 12v at the oil pressure switch first and also at the fuel pump relay "A" terminal.
They should both be orange color.

Edit: this wire also powers the ECM!