1992 Q45 fuel pump modulator

[MarkQ45]

My fuel pump modulator is making a loud buzzing sound. The car, for now seems to be functioning fine. Should I replace it? Could something else be causing it to do this? :help

[greg_atlanta]

Yes, replace the fuel pump. Otherwise it may burn up the computer which controls the fuel pump too (FPCU, fuel pump control unit).

Common failure item at the 80-100K mark, though they sometimes last longer.

[aaacomp]

Have had to replace only one pump at 190k, do it soon since it will cause the pins on the controller to melt and then you'll have to replace that too. BTY you'll notice an increase in performance when you replace the pump.....:thumbup

[MarkQ45]

Thanks, guys for the help. I replaced the pump and all is well. Does anyone know of a good on line source for parts for Infiniti's?That fuel pump price was hard to swallow.

[DAEDALUS]

Infiniti of Scottsdale, infinitipartsusa.com1-888-216-5328They have excellent prices.

[Sopdadope]

I got my fuel pump from Eric SanMiguel for dirt cheap!! $22 to be exact!!! =)

[tangalora]

Here (for others to benefit from) is previously missing important information for diagnosing fuel pump control unit problems in the 1990 Q45 (all of which I learned the very hard way):

female....+.+.... The factory shop manual (FSM) describes the pins as from A thru H.+---+ +---+ in the female fuel pump control unit harness connector (FPCU HC).| A B C D | | E F G H | Looking from the terminal side of the FPCU HC, you can patch E +---------+ to ground to bypass the Fuel Pump Control Unit (FPCU)...^........ ........... Note: Terminals G & D are empty (labelled 3 & 7 on the FPCU PCB)............ ......Solder 16 AWG wire from D to H on the HC (4 to 8 on the PCB).male....o.o.... The printed circuit board (PCB) has a label for pin 4 & pin 8 only.o---o o---o Terminal E (on the FPCU HC) connects to pin 4 on the FPCU PC board.| 5 6 7 8 | | 1 2 3 4 | You can rosin-core solder a 16 AWG jumper from the unused pin 8 o---------o to the charred pin 4 on the UNDERSIDE of the FPCU PCB.........^.. ........... Note: You will overdiagnose the problem if you follow the FSM............ ......I recommend you follow q45tech recommendations + this diagram.

[tangalora]

A real picture is better than the diagram above (which got messed up because it was pure text and the HTML removed all the contigious spaces) ...

Here is a shot of the jumper to ground of the number 4 connection (the one with no terminals next to it) in the white fuel pump control unit harness connector.

So the next poor soul doing a fuel pump test & repair benefits, the following URLs contain many hints & photos.

a) NICO Forums > Online Mechanic > Infiniti Online Mechanic > 1992 Q45 fuel pump modulatorhttp://www.nissaninfiniticlub....=3984b) NICO Forums > Online Mechanic > Infiniti Online Mechanic > Installing Fuel Pump Control Module??http://www.nissaninfiniticlub....36948c) NICO Forums > Online Mechanic > Infiniti Online Mechanic > problem after changing fuel pumphttp://www.nissaninfiniticlub....14348d) NICO Forums > Online Mechanic > Infiniti Online Mechanic > q45 fuel pump/control modulehttp://www.nissaninfiniticlub....34503e) NICO Forums > Online Mechanic > Infiniti Online Mechanic > Fuel pump problemhttp://www.nissaninfiniticlub....11900f) NICO Forums > Online Mechanic > Infiniti Online Mechanic > feul pump control unit (sic)http://www.nissaninfiniticlub....18148g) NICO Forums > Online Mechanic > Infiniti Online Mechanic > Fuel Pump Replacementhttp://www.nissaninfiniticlub....=6268h) NICO Forums > Online Mechanic > Infiniti Online Mechanic > Fuel pumphttp://www.nissaninfiniticlub....47728i) NICO Forums > Online Mechanic > Infiniti Online Mechanic > q45 fuel pump controllerhttp://www.nissaninfiniticlub....73822j) NICO Forums > NICO General > Infiniti General > Fuel Pump Pictureshttp://www.nissaninfiniticlub....d=454k) NICO Forums > NICO General > Infiniti General > Q45 fuel pump modulatorhttp://www.nissaninfiniticlub....13588l) NICO Forums > NICO General > Infiniti General > Fuel Pump Control Module Needed (I'm a moron) http://www.nissaninfiniticlub....36156

[tangalora]

Oh bother. That's what I get for trying to clarify things after the fact.

The photo above doesn't show the shunt connection to the #4 terminal on the white fuel pump control unit harness connector ... it shows the shunt connection to the E terminal on the whte fuel pump control unit harness connector (as described in the previous posts).

Note that the A & F terminal slots have no metal in them (so you really can't mistake the E terminal either way).

If you simply jump this E terminal to ground (with everything but this connector connected), you will bypass the fuel pump control unit altogether, and, if it was shot, then your fuel pump should start working (albeit at constant full 6 amp speed) again. I used my 1990 Q45 for a few weeks in this configuration, until I got around to soldering the fuel pump control unit #4 wire.

The photo below shows the other side of this connection. The photo below shows the white fuel pump control unit connector (integral with the fuel pump control unit itself).

Notice in my case the #4 wire of the fuel pump control unit connector (which connects to the E terminal in the fuel pump control unit harness connector) shows that it saw too much current (probably due to the deteriorating fuel pump which was humming for thousands of miles). It's fried so badly you can see the burn marks.

Interestingly, once I re-soldered and re-inforced that #4 connection to the PC board (and replaced the humming fuel pump), the fpcu worked like a charm and has been for over 10 thousand miles since.