No power going to fuel pump - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

robmontoya11 · 10-12-2015, 11:13 PM

Recently did a auto to 5spd swap and the motor was running great @ 180psi all 4 cylinders until a couple of days ago I went to start the motor and the fuel pump didn't prime and isn't feeding fuel to the motor. A couple days later I go to turn on the motor I went and I replaced some fuses and the starter primed. Then today I went to start the motor again and nothing. I gave direct power to the fuel pump and it works fine so a bad fuel pump isn't the case. Checked the fuse for the fuel pump as well and replaced it, still not the case.

When I put it in ignition mode all power goes to everything but the fuel pump

Could it be a faulty relay, ECU issue, or a ground somewhere?

r20crazy · 10-12-2015, 11:35 PM

check the ground wires that bolt to the head. there are 2 as I recall (but could be one not checking 2night), one come outa the injector wire harness near the firewall (and bolts to rear exhaust side corner of head. other near upper timing cover front near coolant neck(not the one by the throttle body to battery). if loose or not making good contact u"ll have your exact issue. lmk (info provided is for DOHC ka24de s13) may be different for SOHC and s14 but similar

Croustibat · 10-13-2015, 02:37 AM

The ECU controls the fuel pump relay (green wire if i remember correctly). If the engine runs when the pump is wired directly, chances are it is a relay or a wiring problem.

Anyway, if you get blown fuses problems, you might want to investigate them ...

there is a known problem with aftermarket fuel pumps on S13/14 chassis, the wires from the relay to the pump are too thin and need replacing. You can easily check this with a voltmeter, when it happens voltage at the pump is lower than voltage at battery (like 10V or less instead of 14)

edit : it reminds me of another known "electrical" problem : lowered S and Z chassis tend to munch through the electrical harness that pass just up the front tyres (unless you relocate it). Worth checking too ...

Sills · 10-13-2015, 04:10 PM

Theres a relay associated with the fuel pump, as well as the ECCS relay that also must be working to feed power to the pump properly. Break out the multimeter and check the wires where the pump is hooked up.

Sometimes this can happen due to poor seating of the F3 plug. Make sure it is latched in properly. Its possible to have proper power to nearly everything, exept if that plug isnt seated nearly perfectly it wont send power to the fuel pump. Thats the big plug located by the ECU, its white with a black cap. Google F3 plug if youre not familliar, itll come up.

robmontoya11 · 10-13-2015, 04:51 PM

Can't find f3 plug, I disconnected the ECU and reconnected it and nothing happened

robmontoya11 · 10-13-2015, 04:52 PM

And the relays are working properly

Sills · 10-13-2015, 05:53 PM

Quote:

Originally Posted by robmontoya11

And the relays are working properly

F3 plug is located right by the ecu in that footwell cubby. Its an S chassis that youre having problems on, correct? R chassis does not use the F3 plug. Its big and has a latch on it, to seat the plug properly you have to mate both sides then pull down on the latch handle to seat it fully.

robmontoya11 · 10-13-2015, 09:22 PM

checked the plug ad its on right, any other tips?

Sills · 10-14-2015, 10:17 AM

If youre sure the relays are working properly it may be time to take out the multimeter. Start at the pump and make your way up the harness. Possibly consider running new wires for it?

10-12-2015, 11:13 PM	#1
robmontoya11 Join Date: Oct 2015 Location: Miami Age: 27 Posts: 14 Trader Rating: (0) Feedback Score: 0 reviews	No power going to fuel pump Recently did a auto to 5spd swap and the motor was running great @ 180psi all 4 cylinders until a couple of days ago I went to start the motor and the fuel pump didn't prime and isn't feeding fuel to the motor. A couple days later I go to turn on the motor I went and I replaced some fuses and the starter primed. Then today I went to start the motor again and nothing. I gave direct power to the fuel pump and it works fine so a bad fuel pump isn't the case. Checked the fuse for the fuel pump as well and replaced it, still not the case. When I put it in ignition mode all power goes to everything but the fuel pump Could it be a faulty relay, ECU issue, or a ground somewhere?

10-13-2015, 02:37 AM	#3
Croustibat Nissanaholic! Join Date: Aug 2011 Location: France - Toulouse Age: 43 Posts: 1,851 Trader Rating: (0) Feedback Score: 0 reviews	The ECU controls the fuel pump relay (green wire if i remember correctly). If the engine runs when the pump is wired directly, chances are it is a relay or a wiring problem. Anyway, if you get blown fuses problems, you might want to investigate them ... there is a known problem with aftermarket fuel pumps on S13/14 chassis, the wires from the relay to the pump are too thin and need replacing. You can easily check this with a voltmeter, when it happens voltage at the pump is lower than voltage at battery (like 10V or less instead of 14) edit : it reminds me of another known "electrical" problem : lowered S and Z chassis tend to munch through the electrical harness that pass just up the front tyres (unless you relocate it). Worth checking too ...

10-13-2015, 04:10 PM	#4
Sills Leaky Injector Join Date: Nov 2014 Location: Canada Posts: 121 Trader Rating: (0) Feedback Score: 0 reviews	Theres a relay associated with the fuel pump, as well as the ECCS relay that also must be working to feed power to the pump properly. Break out the multimeter and check the wires where the pump is hooked up. Sometimes this can happen due to poor seating of the F3 plug. Make sure it is latched in properly. Its possible to have proper power to nearly everything, exept if that plug isnt seated nearly perfectly it wont send power to the fuel pump. Thats the big plug located by the ECU, its white with a black cap. Google F3 plug if youre not familliar, itll come up.

10-13-2015, 04:51 PM	#5
robmontoya11 Join Date: Oct 2015 Location: Miami Age: 27 Posts: 14 Trader Rating: (0) Feedback Score: 0 reviews	Can't find f3 plug, I disconnected the ECU and reconnected it and nothing happened

10-13-2015, 04:52 PM	#6
robmontoya11 Join Date: Oct 2015 Location: Miami Age: 27 Posts: 14 Trader Rating: (0) Feedback Score: 0 reviews	And the relays are working properly

10-13-2015, 09:22 PM	#8
robmontoya11 Join Date: Oct 2015 Location: Miami Age: 27 Posts: 14 Trader Rating: (0) Feedback Score: 0 reviews	checked the plug ad its on right, any other tips?

10-14-2015, 10:17 AM	#9
Sills Leaky Injector Join Date: Nov 2014 Location: Canada Posts: 121 Trader Rating: (0) Feedback Score: 0 reviews	If youre sure the relays are working properly it may be time to take out the multimeter. Start at the pump and make your way up the harness. Possibly consider running new wires for it?