my f150 wont start?

[truefordman]

Hi I am new to this site. I have a problem with my '86 f150 5.8 winser. My truck does not want to stay on! I can crank it and as long as i hold the key forward it will stay running, if i let go off the key it wont stay on. i have already replaced the ignition module but i have no other ideas at this time any suggestions will be of great help. also any ideas for better gas mileage i have a c-6 automatic with no overdrive :blink:

 

[fordtruckman]

does it take some time for it to start? could it be the ignition switch loosing contact once you let go of the key? what are any previous symtoms ofr history prior to this happening?