DELL DIMENSION E510 Windows XP home power supply

My dell E510 will not power up, no lights on front panel come on. When I remove the 24 pin connector from M/B and jumper the black and green wires the fan DOES NOT start. When I plug the 24 pin connector to the M/B with the jumper still connected all the lights on front panel flash a few times then go off,  I can power it on, and windows xp loads. Does that indicate a bad power supply? If so what P/S should I replace it with if I want a little more power. ty