40h ford 4 cylinder duel fuel . No crank problem, push starter button and starter cranks for a second. Checked voltage at starter s terminal when start button is pushed, and it has voltage for that second, and then no voltage. Can jump across starter terminals and starter will crank. Have voltage thru start relay behind panel. Can jump starter to start engine and engine will backfire and not start. We pulled one spark plug wire off and cranked engine and engine runs. Will not run on fast idle and foot control in basket does not respond. There is a control box with several wire plug and one vaccum hose. Do not know what it's function is. With engine idling, we can tap on that control box and engine will stall. All problems started at once. Have had this machine for several years with no serious problems.