I have a 2000 Ford F150 which just recently got a brand new engine core and with the water pumped fixed plus compressor.

Thinking well the truck should start with no problems yeah for the first couple of weeks but then its failed to start.

I had to sit there for awhile until it fired up. I went to the mechanic and says its the not the battery or the starter and just did re-calibrated the fuel which then the next week it failed again (Mechanic is trust worthy).

I think it needs a new fuel pump. Any ideas on what's going on?