6.5 not starting anymore I think why but not sure.Please read
 

I have a 1998 chevy k2500 6.5 I decided to check and see if the lift pump was working i opened the tee valve at idle and no fuel came out and the truck stalled. i tried to start it again but it won't start. Is the lift pump the cause of no fuel to the tee valve and it stalling? And why is it not starting, since i opened the tee valve did that break the suction so the IP could not suck the fuel?

Yes your on the right track. Get a working LP and go from there. I like to run power and ground directly to the LP just to rule out any wiring issues before replacing, but I'm a cheap bastard.
Been awhile since I've fooled with a post 96 truck but I believe their is a red wire behind the fuse box that you can jump power to and purge air through the filter and t valve once your lp is working. (Or jump the relay)

Better to jump the relay, drove mine 8 hours home pulling a travel trailer with it jumped. If it works while jumped it's your oil pressure switch which I'd recommend bypassing since it's a weak link in the system

As stated opening the T valve for a first check of the lift pump, is a bad idea. It is best to jumper the lift pump to make sure it is working first.

I have seen this issue with a non-working lift pump, many times.

On 1996 and newer vehicles there is a female spade connector between the under hood fuse box and the firewall. It can be hard to see/find, but it is there.

Forums need to change that bit of information for testing the lift pump. It has this result, far to often.

I like to put a fused safety toggle to the female connector for easy priming and lift pump testing. There are several places to mount the toggle right there. You can access 12 volts from the studs on the back of the under hood fuse box.

Always double check a lift pump by trying to pump from container to container after removing. If your lift pump does not pump fuel while installed, but pumps after it is removed, odds are you have a tank sock problem.

If you install a new lift pump and it doesn't work, you still don't know if you have a different issue or a bad new lift pump.

If using an OEM style lift pump, use only an AC Delco or GM for a 1993 6.5. They have higher flow.
The other after market lift pumps do not have the as good of reputation for performance or longevity.