D 350 Pickup L6-359 5.9L DSL (1989)
If the engine is free, check the voltage at the starter during cranking. If the voltage drops more than 2.4 volts, check that all connections are tight
and the connections are ok.
If the cables are correct and the voltage drop exceeds the limit, check the battery for a bad cell. If all cells are Ok, replace the starter.
