1991 Mercury Tracer Starter

new starter,battery,still wont start:

Do you mean it cranks over and refuses to start or just won't crank at all-nothing.

If it cranks and refuses to start might wanna do below to determine if its fuel or spark.

Get a carb cleaner and spray into the carb or the throttle body on an EFI. Did it start and die? If not disconnect a sparkplug wire or 2 and ground it to the engine -have helper crank engine over-do you have a snapping blue spark? If so-you have a fuel problem, check the fuel pressure to rule out the fuel pump/pressure regulator and listen to the injector/s are they pulsing or hook up a noid light. No snapping blue spark continue to troubleshoot the ignition system-power input to the coil/coil,distributor pick-up coil, ignition control module, cam and crank sensors-

Now if it just won't crank at all

Check the battery/connections/starter relay/transmission range switch/ignition switch.