Inspect the drain lines and make sure the lines do not have any loops and are not crimped.

Remove the fuel drain line and install the mercury filled manometer, Part Number ST-1111-3.

Operate the engine at rated speed and no load.

Observe the reading on the manometer. Hold the manometer at the same level as the connection.

Fuel Drain Line Restriction

If the restriction is above the maximum specifications, remove the fuel tank fill cap and check again.

If the restriction is below the specifications when the cap is removed, replace the tank vents.

If the restriction is still above the specifications, inspect the drain lines for restrictions.