In tank pump diagnosis Questions
 

So I'm pretty sure it's my in tank pump I need to replace. What confuses me tho is I can hear the pump prime when I turn the key to "on". But when I disconnected the fuel lines right before the tank selector on the frame and turn the key all the way, no fuel comes out. Fuel should be coming out at that point right?? When I plugged those hoses back in, I then disconnected where they plug into the high pressure pump on the frame and tried to start it. I feel alot of suction from that external pump. Not 100% sure but I dont think a fuel pressure gauge is going to work since my truck wont stay running and only turn over. It will stay running with starter fluid but only until it burns it off. Anything I should check before throwing a fuel pump at it and hope it works? Maybe just the pump strainer clogged?

I just replaced cap and rotor, fuel filter, and TPS.

Don't throw any parts at it, and stop running the pumps dry. It ruins them.

Since you didn't fully-describe how you checked, I'm not sure what it means that you don't see fuel from the disconnected line. You can't see the line while turning the key. Click each of these, read their captions, follow the relevant links, check the NEXT & PREVious captions from each one, and think about how the truck works:

https://www.supermotors.net/getfile/.../dlcjumper.jpg
(phone app link)

https://www.supermotors.net/getfile/...l/fuelflow.jpg
(phone app link)

https://www.supermotors.net/getfile/...sfrinstall.jpg
(phone app link)

If you want more help, put ALL the truck's details into your signature:

https://www.supermotors.net/getfile/...oorsticker.jpg
(phone app link)

I had someone else turn the key while I was under the truck.