Starter makes a grinding noise. and wont start changed starter and have the same problem. changed crank position senser and it worked for a while. changed it again but didnt fix the problem.

Are you saying the starter is grinding but the engine is not cranking, or the engine is cranking and making noise and not starting ?

You need to have your flywheel: replaced.Your starter motor engages against the fly wheel at the back of the motor. Every time your motor stops it tends to be in the same few positions (just the way things work) so there is more stress on some parts of your fly wheel than others. Because of this the teeth wear out on the fly wheel which means the starter can correctly engage on the fly wheel which is the grinding noise.

You mean a noise like the starter is grinding the gear against the flywheel ?

Does it turn over as it grinds or does it just gring?

WHEN STARTER GOING BAD.SOME TIMES YOU TURN IGNITION NO SOUND FROM STARTER.WHEN STARTER GO BAD IT WILL TURN ENGINE OVER VERY SLOWLY LIKE YOU HAVING A WEAK BATTERY.BAD STARTER SOLENOID MAKE CLICKING NOISE ENGINE WONT CRANK.BAD STARTER WILL MAKE NOISEY GRINDING NOISE IF DRIVE PINION GEAR DAMAGED.

check starter check for low battrey volltage

could be, make sure battery is fully charged then have someone hold the key in the crank position while you test for power at the small wire on the starter, if theres power in the crank position then i would say a bad starter, heres a diagram of the wire location.

My first guss would be a fuel pump, just would have to verify that when you first turn on the ignition to crank you can either hear the fuel pump turn on in the tank or not, if you cannot hear the buzz or whine noise from the pump in the tank you need a fuel pump. Fuel pumps are a very common problem with these trucks.

it could be:
1)starter out of work
2)Air filter? Dirty? Clogged?
3)Moisture in disty?
4)Fuel Pump.
Did it make a whirring sound? If so it'de most likely be an electric sensor.
Is it cranking over faster than normal?
This could mean The timing belt is screwed or lack of compression.

Is it cranking over slow? if so then.......
1)Battery Charged? Corrosion on cables or connectors?
Hear any grinding or strange noises when cranking? This could mean the starters bad.
2) Possible Bad connection.

If its not cranking at all other possibilities are......
Bad Solenoid
Starter
Bad Starter Drive
Worn Ring gear