if you have too much ash buildup, sometimes just giving one of a legs a medium tap with your foot or a gentle stir will help....
Also, not sure what CFM fan you have, but try it with a very small opening on the slide so it pumps air in short bursts for long periods... If it's too open you also run the risk of letting to much cold air into the fire...
Lonestar 24" Vertical offset w/ Insulated Firebox & Performer Platinum
Former owner: Jambo Backyard, Klose BYC, Med. Spicewine, Pitts & Spitts, XL & (2) Med. BGE's, 22" WSM & (2) 18" WSM's, 18" & 22" Weber Kettles