1984 GL-10 Hardtop Coupe FWD. EA81, Carter/Weber carburetor.
Fuel pump isn't operating. If I provide fuel down the carburetor the engine will run properly until I stop fueling. Replaced fuel pump, and distributor (to provide proper ignition signal, the shaft had some play). I'm focusing on the Fuel Pump Control Unit (FPCU), but I'm not in a position where I can afford to experiments with a $150 new one without being fully convinced that it will remedy my situation. I need actual diagnostic information about this box specifically.
Does anyone know the actual function of the FPCU? First off I'm a Subaru dealership technician, so I'm certainly not shooting blind, but I can't find any actual information about the operation of the FPCU. Using the factory service manual, Haynes, and Chiltons manuals I've been able to find almost nothing of what kind of output this module produces. The manuals all basically say " if power and ground are there, tach signal is coming in, then the pump will run." Yes, that's wonderful, but run how? From what I've figured the pump produces a pulsing power signal, since the pump does nothing and blows the breaker in the Powerprobe after a moment when I supply power and ground directly to the pump. A replacement pump (new) had the same result leading me to believe the pump needs a on-off pulsing power source to operate the plunger solenoid.
Has anyone ever found a way to bypass the FPCU? if it were as easy as a switch or a relay to provide bypassed power to the pump I would have done that, but that was not successful. Can any of the components inside the FPCU be replaced (resistors, capacitors, etc).
I implore you USMB and your fountain of knowledge!