First time posting, long time lurker, please move thread if in wrong section.

I have a 1999 F-150 Supercab 4.2L V6 2WD

I have had this truck for 17 years. Never had any reliability issues until now. About two weeks ago, it stopped turning on. It would crank but there would be no successful ignition. Every once in a while I'd get lucky and it'd start right up. It appeared that the truck was having issues reading the PATS key. When it would just keep cranking, the fuel pump would never prime. Theft light though was not flashing, it would stay solid, the ABS light would stay lit up as well along with Battery light. The "Service Engine Soon" light would not stay light up at all, the fuel gauge would not show the fuel reading, and the fuel pump would not prime. Anyways, today I removed the aftermarket alarm system it had and patched everything back as it was from factory. The aftermarket alarm's module had a burned plug. The part that burned was the red power cable. Fixing it just engaged the long dormant alarm and thus I took it out. After removing it, there is no way that it would even turn on by chance anymore. I've been reading a lot and haven't been able to find anyone else with an issue as close to mine. (If there is, please link me). Another thing to add is that when it would be left in RUN position (even if key didn't read) , the HVAC system was working about a 2 days ago but now it doesn't function anymore. Any ideas for diagnosing/troubleshooting. My idea was to get rid of the aftermarket alarm, which I did but that didn't work, and replace the ignition switch antenna, which didn't work either.

Thanks in advance

 

You removed the factory theft alarm system? I would expect that to cause problems.

 

No not the factory one. My truck did not have a factory alarm, only a POS aftermarket one that was more of a headache than anything.

 

Sounds like the fuel pump going out. You can get a fuel pressure gauge from the parts house free rental.