S14 SR leaning out after battery drain. Help needed - Page 2 - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Kingtal0n · 07-02-2014, 11:01 AM

SO it seems that something may be up with your fuel delivery. To verify that you are "doing the test right" You need to hotwire the fuel pump to stay on for at least a few seconds.

You can do this one of several ways, the easiest iirc is at the fuse box, apply 12V to the fuel pump fuse to manually prime the system. Determine how much time it takes to get fuel flowing. Alternatively you can ground the fuel pump wire at the ECU which activates the fuel pump relay. Or, you can directly engage 12V to the fuel pump (+ positive) at the rear of the vehicle.

In any case, you need to figure out if the problem is one of these:
1. the ecu is not triggering the fuel pump effectively (but the fuel system itself is fine)
2. you have a blockage in your fuel system, physically restricting fuel flow
3. the fuel pump is not installed correctly, or is damaged internally
4. the fuel system has a leak between the pump and fuel rail causing loss of pressure
5. the fuel pump relay, fuse, or wiring is faulty (poor connection/voltage source)

to assist diagnosis of #1, manually triggering the ecu fuel pump wire (with a ground) will let you know if the ecu is capable of working the pump
for #2 you should start at the front and work your way back. remove the feed line next and see if fuel flows freely from the pump->fuel filter. If that fails, continue working backwards, i.e. remove the filter next and try again. then go to the tank and remove the feed from the tank and try.
After #2 it should lead (follow up) your proceedure to #3 and #4

and #5 may be last or first, depending how comfortable you are with electronics.

Bullett · 07-02-2014, 12:40 PM

Awesome information king. Thank you again. I pulled the feed line and got a good gush. I've yet to check the in tank hose for leaks or the fuse/relay/ ecu. After last night my next guess was going to be the rail itself as I just replaced injectors and also check the pump hose. Honestly with what I've seen, this seems to be an issue with my chassis, so I may just call it a day, move forward with plans to sell the driveline, and start from scratch before the new engine goes in.

Kingtal0n · 07-02-2014, 01:18 PM

If the feed line is flowing well, but the rail's return isnt, the problem must lie between the end of the feed line and the end of the rail...

Removing the rail is simple. Pull it off and inspect it. sometimes, a little piece of rubber from the fuel line gets twisted sideways and lodges itself in there. it doesnt take much. You do not have to remove the injectors (but you may need to later if you cannot find the blockage simply).

If your injectors/computer/maf is all stock, often times it pays to have a spare set of these things sitting around for situations like this. A spare rail with injectors should run you $50-$70 if you are patient enough. Then, you could just swap it out in 5 minutes and verify the rail is good.

Bullett · 07-02-2014, 02:44 PM

Well I swapped injectors when I installed the fpr and wide band. So maybe I missed a step or screwed up. It DID run fine for a few days until I ran the battery out. But physical proof says fuel rail so I'll take another look.

07-02-2014, 11:01 AM	#31
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 42 Posts: 4,829 Trader Rating: (17) Feedback Score: 17 reviews	SO it seems that something may be up with your fuel delivery. To verify that you are "doing the test right" You need to hotwire the fuel pump to stay on for at least a few seconds. You can do this one of several ways, the easiest iirc is at the fuse box, apply 12V to the fuel pump fuse to manually prime the system. Determine how much time it takes to get fuel flowing. Alternatively you can ground the fuel pump wire at the ECU which activates the fuel pump relay. Or, you can directly engage 12V to the fuel pump (+ positive) at the rear of the vehicle. In any case, you need to figure out if the problem is one of these: 1. the ecu is not triggering the fuel pump effectively (but the fuel system itself is fine) 2. you have a blockage in your fuel system, physically restricting fuel flow 3. the fuel pump is not installed correctly, or is damaged internally 4. the fuel system has a leak between the pump and fuel rail causing loss of pressure 5. the fuel pump relay, fuse, or wiring is faulty (poor connection/voltage source) to assist diagnosis of #1, manually triggering the ecu fuel pump wire (with a ground) will let you know if the ecu is capable of working the pump for #2 you should start at the front and work your way back. remove the feed line next and see if fuel flows freely from the pump->fuel filter. If that fails, continue working backwards, i.e. remove the filter next and try again. then go to the tank and remove the feed from the tank and try. After #2 it should lead (follow up) your proceedure to #3 and #4 and #5 may be last or first, depending how comfortable you are with electronics. __________________ 5.3/4l80e/turbo 240sx playthrough: tinyurl.com/4l80er

07-02-2014, 01:18 PM	#33
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 42 Posts: 4,829 Trader Rating: (17) Feedback Score: 17 reviews	If the feed line is flowing well, but the rail's return isnt, the problem must lie between the end of the feed line and the end of the rail... Removing the rail is simple. Pull it off and inspect it. sometimes, a little piece of rubber from the fuel line gets twisted sideways and lodges itself in there. it doesnt take much. You do not have to remove the injectors (but you may need to later if you cannot find the blockage simply). If your injectors/computer/maf is all stock, often times it pays to have a spare set of these things sitting around for situations like this. A spare rail with injectors should run you $50-$70 if you are patient enough. Then, you could just swap it out in 5 minutes and verify the rail is good. __________________ 5.3/4l80e/turbo 240sx playthrough: tinyurl.com/4l80er

07-02-2014, 12:40 PM	#32
Bullett Leaky Injector Join Date: Jan 2014 Location: Valdosta GA Age: 42 Posts: 133 Trader Rating: (3) Feedback Score: 3 reviews	Awesome information king. Thank you again. I pulled the feed line and got a good gush. I've yet to check the in tank hose for leaks or the fuse/relay/ ecu. After last night my next guess was going to be the rail itself as I just replaced injectors and also check the pump hose. Honestly with what I've seen, this seems to be an issue with my chassis, so I may just call it a day, move forward with plans to sell the driveline, and start from scratch before the new engine goes in.

07-02-2014, 02:44 PM	#34
Bullett Leaky Injector Join Date: Jan 2014 Location: Valdosta GA Age: 42 Posts: 133 Trader Rating: (3) Feedback Score: 3 reviews	Well I swapped injectors when I installed the fpr and wide band. So maybe I missed a step or screwed up. It DID run fine for a few days until I ran the battery out. But physical proof says fuel rail so I'll take another look.