I replaced vaccum diafram ,i can press diafram and air will come out of top at firewall ,but still i have no vaccum to front wheel ,front drive is locking in so have i missed a fuse or what,thanks for any help .1998 BLAZER MAIN VACCUM LINE FROM MANIFOLD LINE TO T AT DRIVER SIDE OF FIREWALL ,THANKS TO THE THREADS ON THIS PROBLEM, A GREAT SERVICE FOR BLAZER OWNER