1999 f150 v6 am not receiving trigger signal on red wire to fuel pump relay.

Not sure because of the year but, It may have a fuel pump driver module that is mounted above spare tire on box rail.It supplies power to the pump,if you have it, see if it's clam shelling.

Also check your fuel pump relay.just swap it with another for testing.

I have checked and do not find module. I traced red trip wire and it runs across fire wall to passenger side of engine comp.

The relay is good. If bad it would not cause engine to start and run when 12v is supplied to trigger relay.

But your bypassing the relay.

This is not correct. I am only supplying signal to make relay close. There is 12v coming into relay . But none coming out until 12v is applied to trip coil.

Correct, so the relay is bad.

Inertia switch tripped?

The relay is good. If bad it would not cause engine to start and run when 12v is supplied to trigger relay. Relay is not bad. Let's try again. Relay has five post, 12v in, normally open circuit, normally closed circuit, ground to relay coil, 12 v to relay coil. When I apply 12 v to coil relay trips to supply 12 v to normally open terminal, this supplies 12 v to fuel pump.

The relay is good. If bad it would not cause engine to start and run when 12v is supplied to trigger relay. Relay is not bad. Let's try again. Relay has five post, 12v in, normally open circuit, normally closed circuit, ground to relay coil, 12 v to relay coil. When I apply 12 v to coil relay trips to supply 12 v to normally open terminal, this supplies 12 v to fuel pump. I have checked inertia switch and it is not tripped. Sory I didn't mention earlier.