A few days ago, doing 75 mph in the passing lane, my motorcycle started to feel slightly starved for fuel--slightly low power at full throttle. It took about 8-10 miles before the condition progressed and engine stopped dead. After a 2 1/2 hour wait and 100 mile tow (thank you BMWMOA Platinum Club), I've debugged this to the point that I know the problem is inside the tank (lots of fuel flow but no pressure) and will drain it (it's full of course) and figure out what's wrong later today.

Since the failure, I've been thinking about adding a low fuel pressure annunciator. Has anyone done this, have experience doing it on another vehicle, or have a suggested pressure switch?

The normal pressure in the fuel system according to the BMW spec is 3 bar (43 PSI), +/- 0.2 bar--a 14% range, which means without an O2 sensor AFR has a 7% range Open Loop but that's another thread. My understanding is that the fuel pump can put out 60 PSI or more which means that the return pressure is 10 PSI or more while the injectors are consuming fuel.

My thought is to put a 5 PSI (nominally) sensor switch in the return line and then connect that to a light on the front panel that would signal low return flow. If the pressure dropped below 5 PSI, that would mean the pump or hose or filter or something was acting up. My reasoning on the return line is that it might not be a good idea to add a connection on the high pressure line.

What do you think?
RB