fuel pump relay not getting the signal

[eergsxr]

i have a 93 j30 that has been sitting for 3 years, at first it wouldnt start because the pump was not getting power so i changed the fuel pump relay and still nothing so just to make sure my problem was there i stuck a wire to jump it and the car started right up, the problem im having is that the signal wire isnt teling the relay to open, what could be my problem, keep in mind i just did a engine swap and the car has been sitting for 3 years

thanx in advance for any info

[Q451990]

Unfortunately I don't have any J30 experience. Do you have a copy of the FSM? (Factory service manual)

That would at least tell you the output pin from the ECU that feeds that relay.

Hopefully some of our J30 owners with more experience will chime in soon.

Heath

[elwesso]

Here is the J30 fuel pump wiring diagram. This should get us started. Theres a whole pile of things to look for in the FSM, and Im not feeling productive enough to post the entire exerpt from the FSM.



Looking at the diagram, the relay gets power right from the fuse box, so one would only have to check the fuse, check continuity from the fuse box to relay, and the ground.

[Q45tech]

Note the resistor below fuel pump in diagram, this insures that the pump will run at least at slow speed if the FPCU fails.

Run a jumper from battery to pump + to see if it starts...........

[qsiguy]

The Fuel pump relay switches + power from the fuse to the pump. The FPCU switches the ground to the fuel pump. What exactly did you "jump"? If you jumped the ground then the issue is with the FPCU/ECM. If you jumped the relay + then the issue is with the fuel pump relay/fuse.

I'm assuming you jumped the + because like Tech said, the negative side has a resistor to let the pump run on low speed even if the FPCU fails.

[eergsxr]

correct, i jumped the positive side and the pump turned on, there for i started the car, so im guessing the problem is some were in the signal wires which is not telling the relay to open which connects the positives

[Q451990]

Hmmm... I learned something today! The J has a FPCU too? Is it the same one as in the Q45? Might be another source for used parts... What other Nissan products used a "multi-mode fuel pump with controller" setup?

Heath

[eergsxr]

were is the fuel pump control unit located?

[Q45tech]

Since the fuel demand of a J30 is a THIRD LESS than the Q.........the question is are they the same FPCU [unknown]..................the fuel pumps are definitely different.

Think the equivalence would be the NA 300zx 90-96.

[eergsxr]

ok, but does anybody know were it is, or what does it look like? i have checked evrthing on the car and it all works, so im hoping this control unit went bad on my car

thanx in advance for any info and for everybody's input