Have replaced the fuel pump, getting good fuel pressure. Truck will not crank unless holding down the gas and when it does, white smoke comes out of exhaust and then truck turns off.

Long story...To start...brake line busted and replaced that. When going to start the engine, theft deterrent kicked in. After finally fixing that, truck had same problem. So, I replaced the MAF sensor, Crankshaft position sensor, and fuel pump. Not to mention new plugs and wires. Check engine light comes on and then off and It doesn't throw any codes except yesterday it throwed the PO336 for crankshaft position sensor so I again, replaced the crankshaft position sensor. it cranked up and run sluggish for about 15 seconds , like it had air in the fuel lines, and we thought we had it licked, bit now, back to the same problem. I did remove the wirnig harness for the MAF sensor and it doesn't change anything whether it is plugged in or not.