I have a 2002 with 105,000 original miles on it. 5.4 L. Approximately 1 month ago the truck sat in Texas 105 degree direct sunlight for 2 days. Prior to this had no starting issues. I went to start it in the evening and the engine bumped, dash lights went out, and nothing. Replaced battery, same thing. Replaced starter, same issue. Replaced starter solenoid and ignition switch, still same issue. Verified all ground wires are clean and tight, battery cables are clean and tight, and all fuses are good. One time, early on, there was a small puff of white smoke from the top rear of the engine, but that had never repeated. Also, battery is showing no charge on dash gauge but voltage meter reads good charge. This is my only vehicle right now and I'm at a loss as to what might be the issue. Thanks in advance for any advise!

 

That was the "magic smoke" that made it work.

The obvious observation is that you've lost either the power or the ground feed from your battery. You will need to use your voltmeter and do "voltage drop testing" (Google it) to see where the current under load is being stopped . Also, since you removed the starter relay, make sure you put the cables back on the correct terminals. Don't ask me how I learned that one!

 

When the key is turned, there is significant drop in voltage.

 

Exactly. Do as I suggested.

 

Sounds like the starter is trying to work but it gets stopped then the big power drop. Might try turning the engine by hand to make sure it isn't locked up. Also remove the serpentine belt and try starting to see if an accessory is locked up. Won't hurt to run it for a few seconds without the belt.