On 21 Oct, 09:05, JD wrote:
I have a 4 OHP Quattro Briggs & Stratton engine on my lawnmower, and
when I use the prime bulb to try to get the engine started the priming
doesn't work. I take off the top of the sort of rectangular metal box
that holds the filter, (and the filter appears to be clean), and pour
a little gasoline into the engine and the engine starts up. Can
someone tell me how to get the prime system working again? Thanks,

JD

Read the section entitled "A primer on priming" at:

http://repairfaq.ece.drexel.edu/sam/lmfaq.htm