MRFRED,

Hey, I am looking at doing a rewire, but in a little different fashion. I am looking to rewire the Hot lead from battery to Relay 3. This is the Hot lead, that once the Relay is activated, feeds the Hot lead to the Fuel Pump, which I believe is the White wire coming off of Relay 3. Question is, what is the HOT Wire to Relay 3 from Battery? Having issues reading the color code designations of the plug that connects to Relay 3.

Can you help? Anyone else know?


I have scowered the internet and this forum in search for the Fuel Relay 3 plug color code schematic of wires. I.E. what wire goes where, and color of wire in the plug.

If anyone could help point me in the right direction, would be helpful.

This is the Relay under the hood next to the fuel resistor packs.

Its a 4 or 5 wire plug that plugs into the Relay.

Thanks again,

 

Yes there are diagrams online of this circuit, however they aren't very clear on color code of wires. Need actual color codes and where they connect.

THanks

 

Bump

 

from the manual...

 

So yes, I have looked at this. My question is more, I need to know which wire coming into the Relay is the Battery Hot wire with Voltage and Current to run the pump. I know the white wire in the plug is the feed wire to the actual pump. In theory, the Hot wire from battery is on one side of the switch portion of the Relay, when switch closes, and Relay is activated, the Hot wire from battery connects to Feed Wire of Pump.

Which wire is the Feed wire from Battery?

 

you can either use the pinout of the relay to figure it out since you said you know the function of the other wires or probe around with a multimeter. you have enough info it should not be hard to determine what you want.

 

That's just it, besides the white wire, it looks like all the color coding on the rest are the same. Relay 3 on the relay, and on the power connector, are not labeled with pin-out. See my problem...?

 

i see what your saying now...

it looks like the battery feed is coming from relay 2 and hitting both pin 2 and 4, which turns the relay on and sends power to the fuel pump and the ecu.

pin 5 on C123 should be it.

 

its almost like they are just using relay 3 as a current limiter to feed the ecu.

which means all 3 white wires are basically the same circuit.

 

I answered your question about wire colors in MRFred's fuel pump rewire thread. I'll go into a little more detail here about how the circuit operates. Relay 3 is fed power from Relay 2, which is getting power from Relay 1. So there is no direct line straight to the battery from relay 3. The ECU turns the pump on via Relay 1 and 2, and uses relay 3 to control the current/voltage to the pump. To control voltage the ECU Opens the relay and power flows to the pump through a current limiting resistor, which is low voltage mode Battery -> Relay 1 -> Relay 2 -> Resistor -> Pump. When the ECU wants full power to the pump it closes relay 3, bypassing the resistor and giving the pump a straight shot to the battery through Relay 1 -> Relay 2-> Relay 3 -> pump. If you want to upgrade your wiring to emulate a bypass you will want to upgrade all the wires between the battery, relay 1, relay 2, relay 3, and to the pump, through all the different harness connectors.

 

yea^^^

what he said.

he is correct.!

 

https://www.roadraceengineering.com/...elpumpinfo.htm

This is a better diagram. I see what your saying. For some reason I thought it had a hot wire from the Battery.

I play around a little, and try not to fry an ECM again...lol.

Thanks again.

 

The nice thing about doing a rewire with a new relay and a hobs switch is that you have the New wiring plus the factory wiring going to the pump so plenty of copper there. Also the grounding on the pump should be upgraded to match( I think you said you already did that though).

The FET in the ECU that switches relay 3 is substantially stronger then the one that switches relay 1&2 so you can add a typical bosch style 12v relay onto it without burning it up. Its that particular behavior of Relay 3 that makes it tricky to implement. I went through how i did it in MRFreds thread, my conclusion was for most people the hob switch would probably be the better solution.

 

^^^^
he is correct... again.

 

Bumpski. so @Biggiesacks I'm under the impression if one wanted to replace the factory wiring on the high voltage circuit with some beefier wires that the red is what would need to be changed out? Does anyone know if the factory relays can handle increased amps?