Determining the size of a fuel line in a vehicle or motorcycle is important prior to replacing it. The fuel line, along with the other parts of a fuel system, are responsible for delivering the fuel from the fuel cell into the carburettor. It is important to have the right size so the vehicle operates efficiently. The size of the fuel line is determined by the outside diameter. Completing the measurement is simple and takes relatively few tools. The same steps can be used to measure other types of tubing, such as those for brake lines.
Uncover the fuel line so that it is visible and can be reached easily. Do not remove the fuel line or disconnect it.
Place the top of a 1/4-inch wrench with an open end over the fuel line. Slide it carefully over the line so that it fits snugly against the tubing. Read the wrench's measurements to determine the diameter of the fuel line.
Place a caliper over the fuel line if the wrench did not give an accurate reading. Calipers are used to measure distance between two sides of one object. Adjust the tips of the caliper to fit tightly on either side of the line. Remove the caliper. Place the tips on a ruler and read the measurement.
It is also possible to gauge what size the line is by looking at it and comparing the fuel line to others around it.