First I will start with the back story. I went out to shovel one evening and moved my truck to the street. After I got done shoveling I went to move it back to the driveway when it would crank but not fire. I had it towed to my mechanic. He changed the fuel filter and it ran. On the way home I noticed the tachometer would be jumpy, dropping to 0 then up to engine speed and then to 0 and so on, but there was no pattern to it. Then the engine would hiccup like it was running out of fuel. But only for a moment, then it would run normal. It did this all the way home, being sporadic in the tach and engine hiccup no patterns. So I got home and later went out to go somewhere and it would crank but no fire. hours later I tried it again and it started. I drove it around for like 20 mins added fresh fuel came home turned it off. I immediately tried to start it again....crank no fire. Let it sit for a few hours and it will start. Same tach and hiccups, check engine light is on. Please can someone tell me what this might be. I am fearing the worst if you know what I mean.