New to this site, I have a problem with a used ferris hydrowalk i purchased in run down condition. When I first start the 14 hp kohler it runs fine for a while and then it stops drawing fuel. I installed a new fuel pump but that did not change a thing. I pulled off the fuel line at the carb and fuel pumps out when I turn the engine over. I installed a squeez ball to help keep it running while mowing, runs out quick, have to stop and pump a lot to keep it running. when I shut the mower off lots of little bubbles come up in the fuel tank from the outlet line. Tonight I put my hand over the filler hole on the tank and the fuel filter started to fill up. my cap is broke and I will get a new one tomorrow. Will this fix the problem? why wont it draw fuel with the cap off? Should the cap be vented or unvented? Please help.