Topic: B13 Se-R electrical issue (Help!)

Ok, we're a new team with a "fresh" build 94 Sentra Se-R....

The battery is relocated to the trunk, i have added a kill switch and a keyless switch panel as well as added a tach.

My current issue is the car will not start unless the fuel pump relay is jumped and that tach doesn't work (it is spliced into the #2 wire on the ECU harness)

Attached is my (super fancy) wiring schematic for what I have done to the car to make that happen...

The ECU does not appear to be sending the signal to ground the fuel pump relay or to the tach.

I did cut the wrong blue/white wire in the ecu harness (the one that goes to the small ecu plug) when i first wired the tach, but that has been fixed and i haven't found a bad fuse.

I'm stuck at this point as I'm not sure why the ECU isn't giving the signal....so I come to you, SR20/Lemons experts for ideas where to look next... Thanks for reading my word fort and pointing out the blatantly obvious mistake I have made.
https://imgur.com/gAPq4kC
https://i.imgur.com/gAPq4kC.jpg

Hopefully these pics will link to Imgur.

Re: B13 Se-R electrical issue (Help!)

Go to this link and download the factory service manual for the car:https://nicoclub.com/nissan-service-manuals
If the ECU is similar to all other SR20/KA24 from that era the ECU will not turn on the fuel pump if it does't get a proper signal from the distributor.
When you first apply power to the ECU does the fuel pump run for a couple of seconds then turn off?  If so it's definitely the signals from the distributor.
There's full diagnostic trees in the manual.

Re: B13 Se-R electrical issue (Help!)

it does not prime unless jumped, I do have the service manual....I'll check it out.

Thanks

Re: B13 Se-R electrical issue (Help!)

FWIW we yank the whole chassis harness, run no relays, and fuse the white, black/red, and fuel pump positive wires to their own respective fuses on a cheapo marine fuse box. Ground fuel pump ground wire right there on the fuel pump lid. There's no reason not to run the fuel pump when the kill switch is on, IMO. Ditto fans, hotwire them on low through a fuse and run ground straight to the chassis.

If you don't run alternator's red/white wire to the factory gauge cluster, wire it to 12v through a 100 ohm (I think) resistor. The other wire on the plug gets straight 12v.

Don't bother with ignition switch, kill switch is your ignition switch now. Simple wiring is the best wiring.

K Car Stalker

Re: B13 Se-R electrical issue (Help!)

If you still have it check your ignition switch. I'll bet there's more than just 3 wires on it. You aren't engaging or powering your ECU. Find that wire and make it either connect to 12v or ground depending on what the Wire Diagram says it wants. OR look for an ECU relay either under the dash or under the hood and see where that's being run from and if it's clicking on.

Mistake By The Lake Racing (MBTL)
88 Thunderbird "THUNDERBIRDS ARE GO!", Ex Astris, Rubigo / Semper Fracti
A&D: 2014 Sebrings at Sebring (NSF), 2014 NJMP2 Jurassic Park (SpeedyCop), 2012 Summit Point J30 (PiNuts)
2018 Route Sucky-Suck Rally Miata, 2019 World Tour Of Texas 64 Newport

Re: B13 Se-R electrical issue (Help!)

firegremlin wrote:

FWIW we yank the whole chassis harness, run no relays, and fuse the white, black/red, and fuel pump positive wires to their own respective fuses on a cheapo marine fuse box. Ground fuel pump ground wire right there on the fuel pump lid. There's no reason not to run the fuel pump when the kill switch is on, IMO. Ditto fans, hotwire them on low through a fuse and run ground straight to the chassis.

If you don't run alternator's red/white wire to the factory gauge cluster, wire it to 12v through a 100 ohm (I think) resistor. The other wire on the plug gets straight 12v.

Don't bother with ignition switch, kill switch is your ignition switch now. Simple wiring is the best wiring.

All for simple wiring, but you might want to rethink powering the fuel pump constantly... What happens when you're upside down and the disoriented driver hasn't grabbed the kill switch yet?

I'd run a relay with the signal lead being switched by something like a oil pressure warning sender (no oil pressure, no fuel pressure) but hey...

Tradewinds Tribesmen Racing (The road goes on forever…)
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Re: B13 Se-R electrical issue (Help!)

Thanks for the input.. we permentaly grounded the fuel pump relay and wired the tach to the coil,  everything seems to work as it should.... I did remove the stock instrument cluster and just bundled and tied  the harnesses in back of the dash and I'm just running a monster tach in its place... I can hear an under dash relay click on when I arm the switch and it fires with the button....should I still be chasing stuff for that ecu ground/tach signal?

Re: B13 Se-R electrical issue (Help!)

If it's running properly with the fuel pump forced on, then no, the ECU is probably working and something in the fuel pump circuit must be futzed, floating Ground somewhere? There's always another one of them after you think you found them all.

Mistake By The Lake Racing (MBTL)
88 Thunderbird "THUNDERBIRDS ARE GO!", Ex Astris, Rubigo / Semper Fracti
A&D: 2014 Sebrings at Sebring (NSF), 2014 NJMP2 Jurassic Park (SpeedyCop), 2012 Summit Point J30 (PiNuts)
2018 Route Sucky-Suck Rally Miata, 2019 World Tour Of Texas 64 Newport