Electrically challenged questions

[FDLWproject]

Hi folks - need some input as I slog through the electrical.

I have a 351W/427 from Forte with Edelbrock Pro Flo 4 EFI, Tremec TKX transmission, Holley in-tank fuel pump, and Ron Francis harness.

1. Radiator fan:
This one has thrown me for a loop. I want the PF4 EFI to control the fan on/off (using the fan relay in the Ron Francis panel). On the PF4 body, I have the PF4 water temp sensor + a water temp sensor to run the Speedhut water temp gauge. I'm assuming the PF4 water temp sensor feeds the ECU and based on temp, will provide a pulse to the fan to modulate fan on/off. Coming out of the ECU on the PF4 EFI, there are two leads on the harness that are for fans (both single strand, ground output - there's 2 in case you're running 2 fans). I believe that I can take one of those two fan leads and connect it to the DK GRN FAN THERMO SWITCH. Since there are two of these green wires in the RF harness for thermo switch (one in the front harness, one in the sending unit harness), can I remove the unused one at the fuse panel?

2. Fuel pump
This is very similar to the radiator fan, I think. I want(/need) to use the fuel pump relay in the Ron Francis harness, triggered by the PF4 EFi. On the PF4 harness, there is a connection for the fuel pump, but that would result in not using the relay - which I need to use given amperage. My plan is to use the Ron Francis rear harness and connect the existing RF fuel pump wires to the Holley pump. Then at the fuse box, splice in the PF4 fuel pump wires to the RF relay. It would be PF4 orange (12v) spliced into the RF fuse panel orange wire for the fuel pump. But for the PF4 ground for the fuel pump - would I just ground it to the chassis? No other changes to the RF harness/fuse panel?

3. Reverse lights:
I'm going to wire in reverse/backup lights on the rear. There is a spot on the Tremec TKX for a reverse light switch. I think I can order a reverse light pigtail off of Summit/Jegs etc that has a ground/hot. For the hot wire, will I splice the reverse pigtail into an Ignition hot wire + the hot feeding to the reverse light? For the ground from the reverse light pigtail, can I just ground it to the chassis, and do the same at the LED reverse light side?

4. Sending unit harness
I'm using the Speedhut sensors for water temp, oil PSI, etc. So I don't think I'll need any of the sending unit wiring (unless I use the DK GRN for the radiator fan thermo switch). Sounds like a lot of folks just remove this harness entirely. Anything I need to know before I do that?

[Jeff Kleiner]

Hi folks - need some input as I slog through the electrical.


3. Reverse lights:
I'm going to wire in reverse/backup lights on the rear. There is a spot on the Tremec TKX for a reverse light switch. I think I can order a reverse light pigtail off of Summit/Jegs etc that has a ground/hot. For the hot wire, will I splice the reverse pigtail into an Ignition hot wire + the hot feeding to the reverse light? For the ground from the reverse light pigtail, can I just ground it to the chassis, and do the same at the LED reverse light side?

The reverse switch in the trans is just on (closed)/off (open). The pigtail itself does not get grounded. Run fused hot to one leg of the pigtail then run the other side of the pigtail to the + side of your reverse lamp. Ground the - side of the lamp. When the trans is in any gear other than reverse the circuit is open and there is no power going to the reverse light. When in reverse the switch closes to complete the circuit and there will be power to the light.

Jeff

[Legendary]

2nd what Jeff said. This is my plan. I ran the reverse wire in to the rear RF harness before I installed it. Now I just need to splice the transmission switch out pigtail into my harness.

[FDLWproject]

Thank you both! Any tips on the radiator or fuel pump?

[Pmieras]

2. Fuel pump
This is very similar to the radiator fan, I think. I want(/need) to use the fuel pump relay in the Ron Francis harness, triggered by the PF4 EFi. On the PF4 harness, there is a connection for the fuel pump, but that would result in not using the relay - which I need to use given amperage. My plan is to use the Ron Francis rear harness and connect the existing RF fuel pump wires to the Holley pump. Then at the fuse box, splice in the PF4 fuel pump wires to the RF relay. It would be PF4 orange (12v) spliced into the RF fuse panel orange wire for the fuel pump. But for the PF4 ground for the fuel pump - would I just ground it to the chassis? No other changes to the RF harness/fuse panel?

I haven't installed my motor into the frame yet so I can't speak on the harness stuff. I did however install my engine on a run stand for testing purposes and had to address the fuel pump pigtail on the PF4. I'm running a PF4 for a LS based stroker.
According to the Edelbrock install documentation (mine might be a little different since it's for a LS, but should be very similar), the fuel pump output from the ECU is for 10Amp Max. If your fuel pump doesn't draw more than 10Amps, you should be fine.

I choose to use the Edelbrock pig tail (10A Max) to trigger a relay.

I did the same thing with the fan having the Edelbrock pig tail trigger a relay to turn on the fan(s).

I guess my logic was to isolate the ECU as much as possible to avoid any feedback issues taking out the ECU.

I would imagine a load for the fuel pump (or the fan for that matter) drawing anywhere close to 10Amps would generate heat over time. I would rather that heat be localized to a relay and not my ECU.
Toggling of a relay is very low current in comparison to the fuel pump vs fan.

[Fixit]

This might help

[Buzzsaw]

I have the Pro Flow 4 EFI on my 302, have you looked at the manual that comes with then EFI. It gives you instruction on wiring the fuel pump and fan or fans. It clearly tells you to run everything off the battery. I am sure you can figure out other routings as you are trying to do but that seems risky to me. Hope this helps