My 1998 Exmark runs several minutes and then just quits. Left sit for a while it starts and runs again but quits again usually after a shorter run time. I have checked the float chamber in the carb and it is full. Checked the fuel anti back fire solenoid and it works but I can't always hear it when I turn I turn the ignition key. Does the power feed to the solenoid come directly from the ignition switch or does it get power from a relay?