Final answer:
An abrasion-resistant sleeve should always be installed over the fuel hose when attaching the 4-way flat connector underneath the A-frame to prevent damage and maintain safety.
Step-by-step explanation:
Always install an abrasion-resistant sleeve over the fuel hose when securing the 4-way flat connector to the underside of the A-frame. This is a crucial step in the installation process to prevent the hose from being damaged by the movement and potential rough contact with the vehicle's frame or other components. The sleeve acts as a protective layer, guarding against chafing and wear that could lead to leaks or eventual failure of the fuel line. Ensuring proper protection is not only essential for maintaining the integrity of the fuel system but also for safety, as it reduces the risk of fire or engine problems.