this may be way out there...but could it be this:
NHTSA Recall No. 94V056/Ford Recall No. 94S83
Vehicles: Ford 1987-1994 B600 and B700 medium duty school bus chassis equipped with hydraulic brakes, tilt hoods, 5.9L, 6.6L, or 7.6L diesel engines or 6.1L or 7.0L gasoline engines.
Population: 3,660 chassis sold or currently registered in the states of Connecticut, Illinois, Indiana, Maine, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, Vermont, and Wisconsin.
Problem: The battery power junction block mounted on the right fender apron, which serves as an electrical connection point for several engine compartment systems, is susceptible to road splash. The terminals at the junction block can experience corrosion and can fracture, causing loss of electrical power and engine shutdown. Engine shutdown, loss of power steering assist, or loss of hydraulic brake boost can occur which could result in loss of vehicle control and a crash.
Remedy: Dealers will replace the junction box, main power terminal, the starter or starter relay, and terminals at the existing junction block. The wiring of the hydraulic brake circuit will also be modified by bypassing the junction block. The new terminals will be made from an alloy material more resistant to salt corrosion. Owners should contact Ford at 1-866-436-7332.