A combined system for detecting leaks in an evaporative emission control system and for inflating flat tires. The evaporative emission control system includes a vapor capture canister with a purge valve and a system pressure sensor, and the flat tire repair kit includes a reservoir containing tire inflation fluid, an attachment tube for attaching the reservoir to a tire, and a pump selectively connected to the evaporative emission control system and the reservoir. A controller is configured to perform the following actions: initiate a leak detection sequence by pressurizing the evaporative emission control system, and then performing a leak detection operation by measuring the pressure within the evaporative emission control system over time. A tire pressure monitoring system may be provided, allowing the pump to be switched between performing evaporative system testing and inflating a flat tire.