got a 87 3.9 dak put a new crate motor in it aprox 6 yrs ago motor has about 30000 on it put it back on the road in feb of this yr. now for the prob going up hill it will start to cut off and sometimes it cuts off completely . i have replaced plugs , wires ,fuel pump and rebuilt carb checked timing still stumped . You guys really helped on my 95 so Im here again any ideas?btw truck was parked for approx 6 yrs before Feb an iv owned the truck for 10 yrs.

 

My best guess it is the carb. Possibly a mis-adjusted float.

 

ran fine until about a week ago only problem i had was after about 30 miles it would cut off an i Think i got that problem fixed . does anyone know what the small ceramic block is beside the cab is and what it does.

 

Post up a picture.