Help Please!! 2000 ram van 1500 won't run

Help, my wife's 2000 ram van with the 3.9 six just this morning she says it made a noise like a diesel and clanking noise then lost power and shut off. since then it will fire and sputter for a second like only 1 or 2 cylinders are doing anything then die. she has been complaining lately that it lacks power and is getting bad gas mileage. but it only has 90,000 miles on it and keeeps excellent oil press. any suggestions would be greatly appreciated.

have your fuel pressure checked, make sure it's between 39-50 psi. If not, you could have a bad fuel pump. Also, check your plugs, make sure they aren't fouled. Last, make sure your filter isn't clogged.

i already checked fuel press. and replaced plugs ,wires,and cap and rotor. but since it was towed to the house it won't turn over . tested battery and starter both work fine. when starter engages it just stops and doesn't turn the flywheel. i think itmay be seized up any other things you think i can check before i condemn the motor would be greatly appreciated.