Yea unsure about the sensor..
But I'm also leaning towards a gut load of dirty fuel..

Maybe the pick screen is blocked..

The other thing I was thinking is maybe a hole in the line somewhere. And your getting a varying amount of air in the fuel lines and now it's let go.
If it is a leaking line you should be able to see a wet fuel patch on the lines somewhere being deisel.
Unless the issue is in the tank..
The pick up is easy to get to threw the cargo bay floor.. lift the carpet / vynal and you'll see the access point..