WHEN THE X-COUNTRY BEGAN, THE VACUUM SYS & COMM RADIOS WERE INOP, BUT OTHERWISE, THE INITIAL LEG OF THE FLT WAS NORMAL. THE PLT CHECKED THAT THE ACFT LGTS WERE OPERG FOR THE RTRN FLT, BUT HE NOTED THE FUEL GAUGES INDCD EMPTY (ALTHOUGH THE ACFT HAD BEEN FULLY SVCD WITH FUEL). AT ABT SUNSET ON THE RTRN FLT, THE ELECTRICAL SYS BCM INOP & THE NORMAL LNDG GEAR EXTN SYS & FLAPS WOULD NOT OPERATE. ABOUT 15 MIN LATER, AS THE ACFT WAS NEARING ITS DESTN, THE ENG LOST POWER & THE PLT MANUALLY EXTENDED THE LNDG GEAR, USING HIS FLASHLIGHT TO MONITOR THE AIRSPEED. THE PLT STATED THAT HE SWITCHED THE FUEL SELECTOR & TRIED TO RESTART THE ENG, BUT WAS UNABLE. SUBSEQUENTLY, A CRASH LNDG WAS MADE AT THE TOP OF A RIVER BANK AT NIGHT. DRG AN INVESTIGATION, THE FUEL SELECTOR WAS FOUND POSITIONED TO AN EMPTY TANK & THE OTHER TANK STILL CONTAINED USABLE FUEL. THE PLT HAD ACCUMULATED ABT 7 HRS OF FLT TIME IN THIS MAKE & MODEL OF ACFT, ALL ON THE DAY OF THE ACDNT.