I still believe its a "ground issue"....using di-electric grease at ALL clean connections: verify quality cables (best to go new...cheap enough) are grounding battery to engine block, engine block to frame, engine block to cab (fire wall), cab to frame. Even though the truck starts the ground from the battery to the engine block may not be quality enough (& even if you have all of the above mentioned grounds in place it doesn't mean they are good enough due to grease, loose connections, poor wire end connections, frayed internal ground cables,)....also "if possible" try not to place multiple connections at a single point (positive or negative like your picture above).....hope this helps.