recently i spent many weeks getting a 1980 240 wagon non diesel to re start and run after many years of sitting idle.

i learned a great deal about this fuel system in the process.

i suggest:

you remove the intank sending unit and inspect the pump for failure and while you're in there make REAL sure the insides of the tank are clean and not rusty or sludge filled. if the tank is less than pristine replace it with a good used one.

the intank pump or more likely the rubber line which connects it to the sending unit output pipe has rotted away leaving the main pump to do all the work.

the real weak spot in this years fuel system is imo the fuel pressure regulator. once this gets clogged or obstructed the pressure to the injectors is reduced causing all manner of running issues.

because these injectors are NOT electrical they must have spec pressure to produce a good pattern.