Dude with a Nerf

Dudes!! I've been modding a vulcan for a time, and after doing some steps over and over I've got to the same result, in auto mode darts won't come out. Mods i've done: I replaced the spring, changed the battery for a 12v 1.2AMP solid one (like this one http://www.steren.co...mbo/br-1201.jpg), and I've cut the air restrictor.
I checked the plunger tube head and it's correctly placed. I also sealed it with vaseline (the head where the orange air restrictor goes). But in 'manual' it shoots very well, really strong and far.

I thought if I had misplaced something from the mechanism, the gun wouldn't shoot at all, but maybe I'm missing something. Any idea of what the problem could be?

Any help will be greatly appreciated.

Dudes help!! I've accquired 2 used Nerf Vulcans, I'm affraid they're modded, at least one. This vulcan has shown trouble sending the darts out of the ammo belt from the beginning, but since I removed the AR it just won't let any dart out. They remain stucked in the belt, and I dunno if it has something to do with the spring of the orange thingy that pushes the darts.
Could you please help me out? What could it be? Has anybody experienced any kind of trouble like this?
Thanks in advance!!