The engine control computer, ECM, is located on the inside of the firewall directly behind the glove box.
The oxygen sensor on a 1989 Chevy Celebrity is located in the rear exhaust manifold on top about the center.
The thermostat on a 1989 Chevy Celebrity is located under the water outlet fitting. Follow the upper radiator hose, it will end at the water outlet.
The petcock on a 1989 Chevy Celebrity is at the bottom of the radiator on the drivers side.
On all models of Chevrolet Celebrity with fuel injection the fuel pump is inside the fuel tank.
It is behind a cover on the driver side strut tower.
The 1989 Chevy Celebrity V6 is rated at 130 hp.
Looking in my factory service manual for a 1989 Chevy Celebrity I found no reference to an accessory relay.
The spark plug gap for your 1989 Chevy Celebrity 2.8 V6 is .045".
Are you asking about the starter solenoid? If yes it is on the starter. If you are not asking about the starter solenoid what are you asking about?
Under hood fuses are generally located next to the relay they are for.
It is located on the top center of the exhaust manifold on the firewall side of the engine.