Fuel regulator test routine

I can understand the return valve and spring connected to this to let the overpressure fuel return back into the tank, but when I look into the regulator from the top (outlet end) it seems like there is some kind of diagfram or something down there as well blocking the air from my mouth passing out.

Is the function on the regulator that you'll need a certain pressure from the pump before the fuel in pushed out the outlet aswell as the overpressure return valve ?[/QUOTE]

Hi Kleinum,

I'm totally unfamiliar with your model bike but I'll just work on principal.

Your kind of right the way you say it. There should be an inlet and an outlet that returns back to the tank, also a port for a manifold vacuum line. There is a diaphragm inside under spring pressure. The opening for the return is pre set and it would be not so large. The idea is under zero to light throttle, you have manifold vacuum which pulls the diaphragm back against the spring, uncovering more of the return thus lowering the fuel pressure for light load. When the throttle is opened, you lose vacuum, the port closes back to the pre set position, increasing fuel pressure for load conditions. The rest is done by injector duty cycle.

The way to test is by use of a fuel pressure gauge, either at a fitting on the rail if you have one, or in line. You can apply a vacuum pump to test the diaphragm sealing and to see if it is moving/working by observing the gauge.

I'm happy to be corrected if technology has evolved since I was on the tools....

Hope this helps

Damo

I haven't looked closer into the regulator but there is no vacuum line. All I know is it keeps the pressure around 50psi in the fuel line. Next time I'm working on the fuel system I will take a look out of curiosity.