Hard start when warm
 

ok i just bought a 2001 dodge 2500 and the injection pump and lift pump were put in just under 2 months ago and the truck has had hard start ever since. had it back to the shop and they cant figure it out , replaced the cam sensor. what could this be? it fires up fine when cold but wont like to start after it has be driven . please help[duhhh]

Is it slow to crank and then fires over or is it just cranking away?
Slow to crank:
check all batt connections and make sure they are charged
check starter connections
if still slow to crank it's probably your starter contacts
Cranking ok then check your fuel supply make sure the air/fuel filters are clean..even though the LP is new it can go out.
there's a black rubber plug on top of the fuel tank take it off a poke a hole in it w/an ice pick and replace it...sometimes there can be a lot of vaccum in the tank which can cause fuel starvation if not vented.
other may chime in but that's about all I can think of now.

the batterys are good.. it cranks fast but wont start.. i have a locking gas cap on the truck and when i open it you hear the vaccum release.. should the cap be better vented?

loosen the cap off before your next hard start and see if that helps, How long does it have to sit before there is a hard start condition?