Hello. I have searched and searched this forum and couldn't find an answer to my specific situation. Not saying it isn't here but after 2 hours of searching, I simply couldn't find it. 2005 Kohler Command 25, 650 hours, bought the commercial Great Dane ztr used 2 years ago. Was always maintained by dealer and owned by homeowner. I was mowing yesterday, hit a bump in the customer's yard, heard a backfire and the engine died. Wouldn't start. Got it to the shop and found a no fuel getting to the carb condition. Checked tubes for oil and determined the fuel pump was bad. Replaced the fuel pump and the engine will now start but will only run with the choke fully closed. It also, sometimes, backfires through the exhaust and dies. I have to wait a few minutes before it will start again, with the choke closed fully of course. Haven't checked the plugs yet but that is my next step. Could it be that something dislodged from the old fuel pump and went into the carb? I see where there seems to be a head gasket problem with this brand of engine too. Keeping that in mind. Any other ideas? Thanks.