93 Thunderbird starting issues.
 

Just like the title says. 93 Thunderbird 3.8L 120,000 miles. Runs great but sometimes when ou try to start it it won't start. We noticed that the fuel pump wouldn't kick on intermittently while trying to start so we replaced it. It worked for a few days then it started doing the same thing. It turns over fine but sometimes it starts and sometimes it doesnt. We dropped the tank and checked the wires, tubing and connections. Everything looked ok. It started fine and, again, was fine the next few days. Then it did it again and still does it. It shows no error codes. We've replaced the fuel pump, fuel filter, starter, coil, relays, and ignition. We've checked the wiring, connections, and fuel lines and each time it starts working fine for anywhere from 3 days to 2 weeks but it never fixes the problem. If it happens and you turn the key back and forth several times it will eventually start but we replaced the ignition and key cylinder. Any help would be greatly appreciated.

I believe the fuel pump relay and inertia switch are in the trunk on the driver's side under the carpet. One of those could be the problem.

Right on, Hanky. i would also suspect the relay - specifically bad contacts inside the relay itself. Cold and rusted contacts in the relay will not make the circuit on the first attempt, but as you energize and release the relay (by turning the ignition on and off several times), the relay's contacts clean themselves mechanically and will eventually make the circuit. Too bad you had to replace the pump, I bet the old one was just fine ...

Let us know how it goes, and good luck!