mechanic really messed up several things on my 1996 ford f150 I am still finding things, any way latest problem, truck doesn't want to start after sitting a day or two, eventually does after a grueling starting period, I have had battery tested several times it is good and still any suggestions. Thank you.

during the "gruelling starting period", what is your spark like ? what is the fuel pressure ? and when it starts finally, is there a noted difference? Weak pressure, or weak spark can be the indicator for the tests that follow. You may want to get it to a different shop for help. Motorcraft parts are the best I have used for that kind of vehicle, and I suggest simplifying the diagnosis by having it checked at dealer service.

after finally starting it seems to perk right up. I have had the other issues finally diagnosed at ford dealership am just now working on this issue had take care of other life threatening and major issues mechanic had done first, but this is getting expensive they are telling me they will have to pull the tank I believe to check to see if he hooked up my fuel pump correctly that he also installed.

There may, then be an issue with the part that was used and how it was installed i expect. We always used a complete pump and sender assembly at ford. 9H307. Then the 1 connection was external and it was covered for a year. I am concerned if your mech used some other method. It is cheaper that way but there is a mess of work and liability added. The cheapest way to get the thing complete is a Carter plain box part from napa if you can get it.