Yanmar Injector Fuel Return

We have had a few customers ask about the purpose of the tiny hose that connects the injectors and goes back into the top of the fuel tank.

The little fuel return hose is the fuel return line and its purpose is to drain the tiny amount of fuel

 that seeps by the injector nozzle & valve. The tiny "leak" is intentional and is used to lubricate the internal components of the injector and then returned to the tank. 

So what if you don't have any fuel coming out of that hose? This is an indication that something is not quite right with your injector. It might be time to get your injectors serviced or replaced. The most common cause of no fuel out of the return hose is that the injector is "popping" at too low of pressure or the valve is not sealing completely in between fuel pressure pulses. This leaks the fuel into the engine that would otherwise make its way to the return hose. The injector should remain sealed until the line pressure reaches 2,275psi (most models) at which time it "pops" open and sprays the fuel in a very fine mist.