HI.. I have an 86 dodge ram slant6. and today I was driving around, then I came home topped up the oil and about an hour later when I went out to start the truck; it turns over then stalls after a couple seconds.. I can start it as many times as I want and it just keeps stalling after a couple secs. unless I pump the gas, then it will run as long as I pump it, as soon as I shift into drive it will stall.. I checked the fuel pump it "seems" to be working and the fuel filter isn't clogged. I'm stumped and I was hoping someone can help me

Thanks in advance
Trev S.