My 96 F250 7.3 diesel started for about 30 seconds then died. It was in very cold weather -40 below. So I then changed my fuel filter and added 911 to my filter resevoire.and it still didn't start. Could have I pushed gelled fuel into my pumps?

That's very possible. Here's a link I recently wrote that may help:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-10.html#post1985158

If you have more than one fuel filter, I would change both of them.

Are you using bio diesel or waste veg oil ? Bio diesel should be fine but waste veg oil will be thicker and may not go through the pump in cold weather.