Most meters have a diode setting, but reading noting one way and a resistance reading the other way sure sounds like the diode is good.
The fact that they're vibrating suggests what others have stated, either the barrels are a bit on the slippery side or you have too much vibration, or both. If you have them really bouncing around, they don't go up the ramp. Mine works best around 11-12 volts, they run right up the ramp.