trouble starting after engine is warm

I have a1997 Tacoma with a 2.7 liter engine and 175000 miles. When the engine is cold it starts and runs fine however after its warm and I try to start it it simply cranks and cranks with persistance it will eventually start or I have to wait until it is cold then start it. I changed the fuel filter as suggested by 2carprojack and also did a tuneup added BG 44K to the fuel to clean the injectors and checked the flow out of the fuel pump, nothing has helped the problem still exists. A coworker told me he had the same problem with his truck and found a bad crank sensor was the source. Could this be the cause of my problem? If so where is it located on the 2.7 liter engine and how difficult is it to replace? help whould be greatly appreciated.

Thank you
jesstayl3