I have a 1990 F150 (5.0L) and am having problems with what I think is the computer. Symptoms are: When you turn the key to the first position the fuel pump continually runs (Motor is not running). Check engine light comes on and stays on (Unable to retrieve codes via a code scanner) When and if it starts the motor runs extremly rich and the transmission doesn't shift (E4OD transmission). If you put it in Drive your start out in OD and the convertor never locks up. Also you can not turn the OD off via the button on the dash. When you press it nothing happens. The light never comes on. Any suggestions, I am at a loss!!

 

The fuel pump staying on is usually an indication of a bad PCM ground or PCM it's self.
Check the pig tail connector at the negative batt terminal.