Replaced ECM, does same thing, 12V at injectors but when you turn it over they don't open, have fuel and spark, checked ground for injector harness, have factory manual, checked many sensors with no luck. Cold start works and it fires briefly until the fuel from that is spent. Does not show any error codes. I'm stumped!

If you have fact manual, do a dist resistance check for the signal generator. Your coil, ignitor, or dist is probably bad.

Try replacing the Ignition Control Module (ICM). If the problem persists, replace the distributor. Since these items are expensive for your Celica, consider local salvage yards.