I have a Sears 110,000 BTU Torpedo heater. It starts, ignites, and blows cold air 5 sec. and kicks off. Ideas?

When I hit the start on it starts, I can see the burner ignite, it blows cold air for appro. 5 seconds and kicks off. It appears that it is not pumping fuel, I can take the hose off when it is running and nothing comes out. It is a Sears, Roebuck & Co. Model 356830.