Fuel system

[dm_gsxr]

I've heard the fuel system pressurizing when I flip the red switch but I'm curious as to just what's going on in there. I understand there's a return line. What's that for? I mean, I'm sure that it returns fuel, buy why? Is the system a loop and how does the loop know which way to run the fuel if it's pressurized and there are two lines. If the pump is pushing the fuel to the injectors, is the pressurization a vacuum so that the fuel is pulled back into the tank via the return line?

Based on the snips of info I have picked up here and there, it sounds like when you power up the bike, the fuel system is negatively pressurized. If I used the second key, I would be unable to open the fuel tank. Fuel is pushed down the fuel line to the injectors by the pump. The mapping determines the duty cycle of the injectors and any remaining fuel is sucked back into the tank via the return line due to the vacuum.

The reason I ask I that I'm mounting an aux fuel tank and want to run fuel into the tank . If I plug into the return line (using a t-connector) and turn the valve, will the pressurization go wacky because it now has a new, non pressurized cell of fuel? And then will it suck the fuel out of the aux tank until it's dry and then suck air, and would that cause a problem? (Sounds like it might be an issue

) If I do this, would I let it suck in, say 3 gallons of the 3.5 gallon tank and stop it via the valve before it's dry?

Thanks for any input.

Carl

 

[dm_gsxr]

I cracked the service manual when I got home and I understand a few more things about this bike that I didn't know, or had the wrong info about.

1. Only the fuel pump and line to the injectors are pressurized. The return line and feed line are not.

2. The fuel pump is external to the tank. Here I thought it was internal.

3. The fuel filter is actually inside the fuel pump.

So the simplest solution would be to tap the return line with a t-connector, run the hose to a pump, run a hose from the pump to the t, run a wire and install a switch to the dash. When the fuel gets to the red line, turn on the valve, flip on the switch, watch the fuel guage move up to "F", flip off the switch and close the valve.

The relief valve in the fuel pump is only activated when the pressurization in the fuel pump reaches 64-85psi so there's no chance of a back flow of fuel into the pump.

And some additional info I picked up along the way:

When the bike is powered on, the ECM powers up the fuel pump. At the end of three seconds, the power is disconnected.

When the engine is cranked and running, the ECM powers the fuel pump.

A tip over sensor is located under the tank hinge. If the bike exceeds 43 degrees, the ECM cuts the power to the fuel pump stopping the delivery of fuel. Power is also cut to the injectors and coil which kills the bike.

There. The things you can learn from a service manual

Carl