Trimmer Fuel Lines

During the process of replacing the Starter string on the String Trimmer I had some tuning issues with the Fuel System.  In the process of trying to tune the carburetor I managed to crack one of the fuel lines.

The last time I replaced the fuel lines was a couple years ago when I had taken the String Trimmer to Mower Medic for a tune up.  Before pulling the old lines off I wanted to take note of where they are attached to the carburetor, and differentiate the lines in the tank.

The first line I am going to work on is the primer return line.  The primer circuit pulls fresh gasoline into the carburetor before starting.  This fuel line send the extra gasoline back to the tank.  This is the line that is cracked also.  I'll pull the old line out of the tank and off the carburetor, and then cut a couple pieces of new lines to replace them.  There is a fitting there to connect the two lines together.

The second fuel line is the source line for the carburetor, which has a filter on its input which lives in the tank.  When replacing this line you need to start with a piece that is about six inches longer than it needs to be.  This is because we need to install the filter on the end of the line, in the tank.

I removed the fitting and the filter from the old fuel line, then measured and cut new pieces of fuel line.

I push the in tank fuel line almost all the way through the tank, so that I can grasp the in tank end of the fuel line to install the fuel filter.  Then we'll install the fuel filter, and pull the fuel line back out of the tank, over by the carburetor, until the filter is in the middle of the tank.

Next we'll trim this line about the same height as the other in tank line, and add the carburetor end of the fuel line.  This is a dual tube fuel line setup because the grey tubing has a better outside diameter for sealing in the tank, and the green (Tygon) tubing has a slightly tighter inside diameter for fitting on the nipples on the carburetor.

Now that the new fuel lines are installed I would normally test the String Trimmer right away, but there is another problem that is directly associated with the fuel lines, and primer system.  The primer bulb is cracked.

This bulb is the pump which primes the carburetor for starting.  Obviously chen its cracked its not going to do its job, because its not sealed, and leak gasoline all over the place.

There are two screws that secure the primer bulb with the clamp plate.  These two screws also hold the body of the carburetor together, so you don't want to move the trimmer around when the carburetor is open.  When putting the carburetor back together, make sure that the carburetor pieces, and gaskets are aligned before torquing down the bulb clamp plate screws.

Now, with the fuel primer bulb repaired we can finally test our new fuel system components.  This is not a full fuel system rebuild, just patching a few things here, which is the norm on this decade old String Trimmer.  A full rebuild would include a carburetor kit, which includes gaskets and small parts to rebuild the carburetor, and we would replace the fuel filter as well.  While we're in here, don't forget to clean and oil the air filter.