EnthusiastMan
04-05-2007, 08:49 PM
Hey guys, I've got a rather confusing problem that I've been dealing with quite some time here. I've tried just about everything and now have to hand it over to the very capable hands of zilvia. Let me just start from the beginning...
Okay, so I've got an 89 S13 with an S14 SR swapped in. I sent my harness to Wiring Specialties for the conversion(great work btw). Got it back, plugged everything in and am confronted with a dead ECU. I order another ECU off ebay(it was $50, so don't judge me :/), and slap the bad boy in. The ECU is powering up now, but no power to the fuel pump. Then begins the routine checks for no fuel pump power:
-check relay
-check fuse
-check pump
-check wiring...
Everything checks out ok. Now, there is a black/pink wire that I've traced from the fuel pump relay that is supposed to be grounded to switch the relay over which powers up the fuel pump. When I manually ground this wire, all is right with the world. The car fires up, runs like a dream. I could just run a toggle switch or bypass the relay but I want to fix it right.
After countless hours of viewing the FSM I have traced that black/pink wire back to the ECU. All you S14 buffs will notice right away that the fuel pump wire for the S14 ECU's is black/yellow. You'd be correct on this assumption but because the harness is off an S13, the black/pink wire off the S13 harness is spliced onto the Black/yellow wire at the ECU. Here is what I've found out so far.
When I hook a volt meter to this wire with the key on I get 12V's. This wire is supposed to be grounded when you turn the key on but because mine isn't working right, I'm not getting that ground, just the 12V. I have sourced this 12V coming from the relay. So what is happening is the relay is supplying the ECU with 12V's along that wire and then the ECU is supposed to ground the wire back out to the relay. It's kinda like the relay is telling the ECU, "hey it's ok to ground me now".
Am I correct on my findings? I'm thinking it's the ECU but the guy I bought it from said everything worked fine with him and Yuri at WiringSpecialties keeps telling me it's a ground loose on my chassis harness. I've quadruple checked my grounds and I just really don't see how a chassis ground can affect the fuel pump relay UNLESS there is another ground coming the ECU that runs into the chassis harness and I am just blind and can't find it.
Any info you guys can give that could help me would be greatly appreciated. If I can't figure anything out I was planing on just going with a power fc since my current motor setup won't run right with a stock ECU, but I would much rather go with an ECU tune if I can resolve this issue without having to replace my ECU. Thanks for any help.
Okay, so I've got an 89 S13 with an S14 SR swapped in. I sent my harness to Wiring Specialties for the conversion(great work btw). Got it back, plugged everything in and am confronted with a dead ECU. I order another ECU off ebay(it was $50, so don't judge me :/), and slap the bad boy in. The ECU is powering up now, but no power to the fuel pump. Then begins the routine checks for no fuel pump power:
-check relay
-check fuse
-check pump
-check wiring...
Everything checks out ok. Now, there is a black/pink wire that I've traced from the fuel pump relay that is supposed to be grounded to switch the relay over which powers up the fuel pump. When I manually ground this wire, all is right with the world. The car fires up, runs like a dream. I could just run a toggle switch or bypass the relay but I want to fix it right.
After countless hours of viewing the FSM I have traced that black/pink wire back to the ECU. All you S14 buffs will notice right away that the fuel pump wire for the S14 ECU's is black/yellow. You'd be correct on this assumption but because the harness is off an S13, the black/pink wire off the S13 harness is spliced onto the Black/yellow wire at the ECU. Here is what I've found out so far.
When I hook a volt meter to this wire with the key on I get 12V's. This wire is supposed to be grounded when you turn the key on but because mine isn't working right, I'm not getting that ground, just the 12V. I have sourced this 12V coming from the relay. So what is happening is the relay is supplying the ECU with 12V's along that wire and then the ECU is supposed to ground the wire back out to the relay. It's kinda like the relay is telling the ECU, "hey it's ok to ground me now".
Am I correct on my findings? I'm thinking it's the ECU but the guy I bought it from said everything worked fine with him and Yuri at WiringSpecialties keeps telling me it's a ground loose on my chassis harness. I've quadruple checked my grounds and I just really don't see how a chassis ground can affect the fuel pump relay UNLESS there is another ground coming the ECU that runs into the chassis harness and I am just blind and can't find it.
Any info you guys can give that could help me would be greatly appreciated. If I can't figure anything out I was planing on just going with a power fc since my current motor setup won't run right with a stock ECU, but I would much rather go with an ECU tune if I can resolve this issue without having to replace my ECU. Thanks for any help.