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1990 should have a CEL(check engine light) on the dash
It should come on with Key ON, that means computer has powered up, having fuel pressure means computer has powered up
CEL should go OFF as soon as starter motor starts to turn the engine, that means computer is getting a Timing Pulse from TFI spark module so will start to open the injectors, no timing pulse = no injectors
If engine starts by adding fuel manually, 50/50 test, that means you have spark, and correct spark timing, and compression
So all that's left is FUEL delivery
FUEL meaning something that a spark can ignite, gasoline has a fairly short shelf life, 5 to 6 months, and all gasoline has some water in it
Water and gas can't bond/mix, and water is heavier than gasoline so it will settle to the bottom of the gas tank if vehicle sits for a few days
Check if you have FUEL, crank the engine over a few times and pull out one spark plug, easiest one to get at
Use a lighter or match to light the tip of spark plug, should ignite easily and burn
If not you don't have FUEL
If tip is DRY you don't have working injectors