i have a 2003 f-150 with a 4.6 it will not turn over replaced battery and starter.still just clicks and every once in a while it trirs to turn over but sounds like it drags

 

You probably need to find the bad cable. That is most likely the big red one. They like to rot from the inside out....specially down by the starter where they loop.

Usually occurs after a pinhole has developed in the insulation. Can't see the corrosion because the cable corrodes inside the insulation. It can disintegrate with time one cable wire at a time until your battery can no longer provide the proper current to the starter.

This is just one scenario. Any of your cables can be bad or not grounded properly. The most common are the two positive cables large and small (6awg and 10 gauge). The frame ground is another that losses contact. This ground is behind the passenger side wheel.

You could also have a bad relay on the firewall.

It helps to be proficient with a multi meter when trouble shooting. These meters are easy to learn how to use and just a cheap little digital meter is good enough.

Good luck and if you suspect internal corrosion, just flex the cable by hand. It will give off a cracking sound, perhaps even a little corrosion dust vs flexing normally.

 

i hav changd battry startr relay and all cables. to start with when i tried to crank it it would just click one time and now it clicks repeatdly and still will not turn over

 

Probably should just take it in. I think it will be cheaper for you to do that at this point.