Measure the current as the pump ages. I goes up like any used electric motor..........look at the current waveform, you'll see that each commutator varies in shape and current.........changing pump's normalized speed.I suspect the fpcu was designed to fail to get owners [attention] to replace noisey pumps caused by water injestion.
They used the same design for 6 years, then in 97 they added a big safety resistor around the unit [pump to ground] to share some of the current load.
My first [fpcu] unit was not changed until 14 years old when it finally became intermittent............after being used on 3 fuel pumps....[none failed just got too noisey for me].
260,000 mile life is good enough for me.
Chicken or egg..............but when a load draws more than design current you cannot fault the controller for over heating and eventually failing.
Years ago I mentioned getting a 15 amp 3 position switch and wiring it in the line between the pump and controller: On#1 to controller, center open, On#2 to ground.........perfect fail safe, perfect car theft immoblizer..............mount inside rear shelf storage tray...........could be a keyed switch for more protection.
The problem with the resistor safety bypass is heat generation, never tried to duplicate but 6-8 volts x 4 amps= ~~ 30 watts.
Someone could experiment and determine what value works the pump at minimum usable speed with no [open circuit] controller.
http://www.stealth316.com/2-fuelpumpguide.htm
http://www.lindertech.com/fuelpump.htm
"Most OEM's suggest removal of the entire fuel tank and a total flush of the tank unit prior to pump replacement.
Repair facilities have shown some reluctance to do this service as suggested! This will compound the damage done to returnless systems as multiple pump replacements are common on these vehicles"...........because pumps only have 12 month warranty and most last longer than this without the tank removal service!
Other manufacturers COPY Nissan FPCU:
http://www.babcox.com/editorial/us/us50146.htm
Can't wait till the new returnless systems start throwing a fit!
It will cost $1000 every 70,000 miles.
Attachment: 
