injection pump ? need help asap
 

so i bought an injection pump off a guy on the vw forum, its a vw 2.8 pump, which was never offered in the usa, this pump came from the uk, and im going to use it on a vw ahu tdi motor, question is, i just got it in the mail, opened it, tried to rotate the sprocket, and it doesnt wanna turn, it will go maybe 1/4 turn and then stop. its very tight, is something wrong?!!! i need to know asap, so that i can return it to the guy if it is broken. this is my first diesel pump i have ever messed with

sposed to turn freely...scott