What action should be taken if air is found in the fuel system?

If air is found in the fuel system, bleeding the fuel lines is the appropriate action to take. This process involves removing the air from the fuel system to ensure proper fuel flow and engine operation. Air in the fuel system can cause issues such as misfiring, stalling, or reduced engine performance, as it interrupts the seamless flow of fuel needed for combustion. Bleeding the lines helps to eliminate those trapped air pockets, allowing for a smooth delivery of fuel to the engine.

The other options may not directly address the problem of air trapped in the fuel system. Replacing the fuel pump is an unnecessary step if the issue is solely related to air presence. Checking air filters, while important for maintaining optimal air intake, does not resolve the fuel system's air problem. Reducing engine speed could temporarily mitigate the effects of air in the system but does not rectify the root issue or restore full performance.