The stock amp in a 1990 Mercury Grand Marquis is in the dash behind the radio.
you dont
No
counterclockwise
8 spark plugs
YES , a 1990 Mercury Grand Marquis 5.0 liter V8 engine has a PCV valve ( Motorcraft part number EV-98-B ) going into the intake manifold
For a 1991 MGM the clock fuse is #8 lgt. blue 15 AMP
have your starter tested, the solenoid on the starter sticks sometimes
Is the big silver plate on top of the engine that reads 5.0.
Check the engine end of the upper radiator hose
the fuel pump is located inside of the gas tank.
For a 1990 Mercury Grand Marquis : According to my Chilton's Auto Repair Manual : ( 20.0 U.S. gallons with the 5.8 liter / 351 cubic inch V8 ) ( 18.0 U.S. gallons with the 5.0 liter / 302 cubic inch V8 )