Starting

The other day my truck died on the
interstate, and would not start back up.
Had it towed. It has 55-60 psi at the fuel
rail, the only code was after trying to start it
the P0340 popped up. Replaced cam shaft
position sensor. Still won't start. Checked
for spark on all right plugs, it's getting fire.
While checking compression, the starter
stopped engaging the flywheel. Spins but
doesn't turn the flywheel. I pulled the
starter and the shaft was loose. Replaced
with a new starter and same thing, starter
spins, won't engage the fly wheel. These
are two separate issues I believe. The truck
is the 5.3 liter with engine code 3 for the
vin. It also has the fuel driver module and
fuel pressure sensor rather than a relay and
fuse for the fuel pump.