Hello friends I am once again in need of some help I have a 91 civic si that i just upgraded the fuel system on i added a FCS 12 gallon fuel tank Vibrant AN fitting and steel braided line 2 fuel filters skunk2 fuel rail aeromotive fuel pressure regulator and a Walbro 255 inline fuel pump. The problem I am having is that i cant get the fuel pump to prime when i turn key to on position and the fuel pump wont kick on when i try and start car Im running a ground to pump and positive wire to a relay i also have ground on relay and a 12v source and I have a wire running to ecu pin a17 i believe is fuel pump is there something i am missing or something i have done wrong sorry for the bad explaination on how its set up any question please feel free to ask. Pump is brand new and does work with direct 12v source but i would like to have car run like stock with no need for fuel pump toggle switch.

 

Here is basically what i am using as reference for wiring

 

I don't think hooking up to the fuse alone is going to work.

What did you do with the old fuel pump wiring?

Why not just hook up the fuel pump from the main relay? There's a large yellow wire at the main relay. Cut and splice into that, it will work just like stock then.

 

are you OBD0 or OBD1?

fuel pump control on OBD0 is ECU pins A12 and A14 (wires connect together inside harness) - wire colors Green/Black

fuel pump control on OBD1 is ECU pins A7 and A8 (wires connect together inside harness) - wire colors Green/Yellow

I believe you would be better off using the stock main relay which is actually two relays in one with first part supplying battery voltage to the ECU, power to the Injectors and power to the 2nd part of the relay - the 2nd part is energized for 2 seconds when the ignition is switched on, and when the engine is running, which supplies power to the fuel pump

 

I am running a obd1 ecu p28bwith s300 i also have a rywire engine harness i will try to connect direct to stock main relay i assume this is it would i connect to that green/yellow wire yiu mentioned

 

i will try this I left all stock wiring in car just in case.

 

as Tyson said, just connect the fuel pump power wire to the yellow/black wire that originally went from the Main Relay to the stock fuel pump and ground the fuel pump

 

at the pump there was 2 wires one im assuming was ground will that have to be grounded or left alone

 

one wire (red in your diagram) is power and the other wire is ground

 

i meant at original pump plug under rear seat. But im trying it right now i ran positive side of Walbro pump to original plug under seat and negative side to black on plug but no prime and pump doesnt turn on

 

why do i feel like your not looking at the fuel pump wiring and your looking at the fuel sending unit (the floater) wiring

 

Yeah probably. The fuel pump wiring is not under the seat. It's way back closer to the where the fuel intake pipe is.

 

The harness under the seat has 4 pins....2 of them aren't the fuel pump power/ground?

 

I guess I was wrong.

you have to drop the tank to access the fuel pump tho.

the EG's i believe have the fuel pump under the seat in a convenient way.

 

Wow, ok. I've been chasing my tail trying to figure out why I'm not getting gas. Assumed it was a bad pump when I didn't have power at that harness. What's the best way to hard wire the pump to test it then? Jumper at the relay harness with the relay removed?There's nothing else closer to the pump?

 

best way is to use the harness on the pump side since your not going to use the stock pump anyway
you can use the plugs from the stock pump and soder them or crimp them into your new pump

goodluck with your project
have anymore questions feel free to ask

 

I'm not the guy who started the thread....I sorta hijacked it by asking about that harness under the seat. I'm trying to get my freshly installed B16a to run....wasn't getting fuel, can't hear the pump kick on, main relay seems fine. Trying to use the stock pump for now just so I can verify the engine is good.

Sounds like I will just have to drop the gas tank and do some more investigation if I can't get it to run by forcing power from the Main Relay harness?

 

i removed original tank the pump wires and sending unit wires all ran same way to the plug by tin cover under rear seat.

 

 

Oh well. I guess it's been awhile for me.

 

No worries. Glad to get it straight.

That picture is one I haven't been able to find and is exactly what I needed. Thanks