deilenberger
A bozo on the bus
The FPR is an active device that works ALL the time the pump is running. The pump output is in excess of the pressure the injectors need. To regulate the pressure, part of the pump output is routed back to the tank from the FPR, the other (regulated) output goes to the fuel rail. The FPR also reacts to vacuum, upping the pressure when RPMs rise. Since the L-Jetronic is a "dumb" system (no feedback loop on actual mixture to the ECU), it relies on having the correct fuel pressure for the conditions the engine is running at.The fuel pressure regulator is something I know nothing about. Heck, I didn't even realize that there is such a device---there again, can't see the forest for the trees, I guess. Maybe that could be the culprit, too. Is that what Don was talking about a while back; the device that relieves the pressure if the fuel line/pump gets blocked?
The FPR is not actually easily visible. It mounts to the back side of the throttle-body assembly, and can only be seen/touched/replaced by removing the bottom half of the air filter box, and going in from the starboard side of the bike.Sorry, but I've not much of a clue as to where to look for it, either. In the tank or tucked away somewhere else? Yikes. This is a bit daunting but I'll await your response before proceeding further than installing the new filter today.
They can go bad in several ways - a punctured diaphram in one will result in raw fuel being dumped into the rear most cylinder (where the vacuum line to the FPR connects.) Or if it sticks shut, fuel pressure will go up, mileage will go down, and there is a possibility that the pump may start chirping just like yours is.
The test is a fuel pressure test. Easy to do, requires a decent pressure gauge, a good fuel-line T and some hose and clamps. This test will show up problems with the FPR toot-sweet so to speak..