I was wondering I recently came across a Volo 850 and to my discovery the batter is dead, so I jump started the car with my other vehicle and the car started up but a little hard. Once I got car running I decided to remove jumper cables and the car suddenly died. Which either A led me to think battery was really no good, or B the alternator is shot and not charging also maybe my car was not enough power to push a little juice into the dead Volvo. So then I decided to try again but this time leave the power jump cables attached and let car run for sometime and heat up so I could check for mechanical issues and operation of motor however, after reving the car for sometime to power it I decided to let off the gas pedal, keep in mind jumper cables still intact and the car will not stay running unless I compress the gas pedal allowing the car to rev slightly beyond the idle speed. So my question is, Is the battery just really dead and maybe alternator or could there be some other issue possibly because once started the car won't stay running on its own even when plugged into my car? Please help getting car for free and its really clean and nice I want to make sure its worth getting especially if all it is is the battery and alternator.