You have a trapped air bubble. remove the cartridge. take some grease from your Wheel bearing tub and pack some down into the pump head. If your grease gun doesn't have an air purge on top. little button you push down while pushing the rod back in. Then screw the cartridge housing on till hand tight then back off about 1-1/2 turns.Then push the rod back in. This will help release any trapped air.Then tighten the housing. Once you get the gun working. let gravity help you. Hang the gun so that it is pump end down. They can be a pain in the buttocks. But the method I gave above has worked well for me. Brian
Last edited by brian0605; 06-19-2007 at 10:30 AM.