2001 ford ranger 2.3L 5 speed. The truck will not start in cold weater ( guess around 40 deg and lower). Last year the truck would not start all winter. I tried to start it this summer and it fired up and ran fine until now, when cold weather starting to set in here in illinois. The truck will crank but will not start. The plugs were changed maybe 2 years ago, it does have spark on the cold days, and the fuel pump does hum when key on. Any Ideas?