I am thinking about buying a 1998 F150 bifuel that was owned by the county. It has the tanks still but it looks like the dashboard switch has been taken out. Should I replace it or should I not even buy the truck. Can I remove the propane tanks and anything that goes with it? Please comment.
If your truck has an OEM propane (or CNG) system, the alternative fuel system may be disabled because of the problematic Compuvalve. This is an expensive item to repair and there is no guarantee that the repair will be any more reliable than the original part.
The best repair would be to reflash the PCM to a standard gasoline system and use a good aftermarket injection conversion (like Technocarb's ESIP). Since the truck is already equipped with a LPG (or CNG) tank, a major expense in a conversion is already paid for. When gasoline prices start to rise again, you will appreciate the ability to switch to a cheaper fuel.
Once you find out whether it is LPG or CNG, check around to see the going price locally. If you're in UT (for example), CNG is going for around $1/gallon GGE.