At about 10:00 EST, a Piper PA-28R-200 made a forced landing in a field shortly after takeoff from South Jersey Regional Airport. The pilot was unhurt. The pilot was planning to practice maneuvers for his upcoming commercial checkride when he was told the airplane was down for maintenance. He waited, and was then asked if he objected to making the first test flight of the rental airplane. He said the run-up was normal and he departed runway 26. At 50 feet, the engine began to backfire and lose power. At 350 feet the engine lost all power. A mechanic at the flight school that operated the airplane said the maintenance performed on the day of the accident consisted of reconnecting a manifold pressure line that had come loose. An apprentice performed the maintenance and an A&P approved the work. No entry was made in the engine logbook. An inspector found the #3 cylinder intake manifold tube disconnected from the engine, but the bolts and washers that connected it to the cylinder were not found.