Lift Pump Powered By "Fuel Pump (FP) Relay"

[Modified]

I am PLANNING the installation of the Mega Fuel Filter, with a lift pump in my 2002 Chevrolet Duramax Allison HD, and all info is referenced to the 2002 Helms Manual. I would assume other years may be similar.
I believe, (SORRY, NO SCIENTIFIC EVIDENCE), the gas problem is due to additional vacuum generated by the secondary filter and engine heat, is promoting more off gassing, so that is why I want to install the lift pump with the secondary filter. I certainly don't want to install additional equipment that could reduce reliability, but with a Lift Pump Bypass valve, knowledge of potential 60K life, and carrying a spare, I believe this so called risk, is acceptable.
I wanted to power the Lift Pump off the Ignition in Run, to reduce battery load during cold, winter starts, but I could only find this source from the In The Cab, Fuse Block Right. This was not convenient, since all my wiring is from under the hood, so I will settle with Lift Pump power in Run and Start, powering the existing Fuel Pump (FP) Relay, located in Fuse Block Underhood, (Helms 8-183). This relay was not used in my truck, but may be wired if anyone has a dual tank option, that may be available in some trucks, but not mine.
Helms talks about a dual tank option, which has a electric fuel pump, plumbed between tanks. This relay coil is only controlled by the ECM, Connector 2, Pin 9. The Primary, and Secondary Tank Level Senders supply a signal to the ECM at Connector 2, pins 54 and 73. I can only assume the ECM will automatically transfer fuel from the secondary to the primary tank, when secondary tank fuel is available, and the primary level is low enough to request more fuel, but I can not verify this as fact.
I don't have this Lift Pump or Mega Filter installed yet, but with preliminary testing and the Helms schematics, I don't see any reason why these directions won't work. I thought I should pass this on soon, because this is a popular mod.

Cautions :

1.) As always when working with electronics, disconnect both batteries before doing any wiring.
2.) At least with my truck, when the Fuse Block Underhood is rotated up to gain access to the four connectors under block, connectors C1(Gray), C2(Black), and C3(Red) are oriented with letters across the top A thru F, left to right. Connector C4(Green) is orientated 180 degrees, with letters across the top, F thru A, left to right. This also causes numbers opposite, from top to bottem. DON'T ASSUME all connectors are orientated the same, read the letters and numbers on each connector.

How To Wire "Fuel Pump (FP) Relay" To Ignition Power

I plan to wire the Fuel Pump (FP) Relay Coil by removing AND INSULATING the DK Green and White wire to the coil, (coil control signal from ECM C2, Pin 9), at Fuse Block Underhood, Connector 2, (Black), Pin B7, (Helms 6-2826). I now will connect a jumper wire from this C2, B7 pin, (coil +12V terminal), to Fuse Block Underhood Connector 4, (Green), Pin A-1, which is ignition power from 10 Amp fuse IGN E, (Helms 8-53). The other wire to the Coil is already grounded. Now my Fuel Pump (FP) Relay will cycle with keyswitch in Run or Start.
I found the following GM crimp connectors, which should work for all Fuse Block Underhood connections, for the approximate wire sizes:
GM # 12110844 approx. wire sizes 20, 18, 16, and maybe 14 gauge
GM # 12110842 approx. wire sizes 10, 12, and maybe 14 gauge, or two smaller gauge wire

The Lift Pump 12V supply power from 20 Amp ECM B fuse to the Fuel Pump (FP) Relay contact, is already wired, (Helms 6-2826). This ECM B fuse also supplies power to the TCM, ECM, and IGN 1 relay. Ensure this ECM B 20 Amp fuse is large enough for your brand of lift pump, and the other existing loads. All you need to do is install a wire at Connector 3 (Red), Pin F1, which will be your 12V power from the relay contact to the electric lift pump. Looking in the Helms Manual, GM uses 1.0 mm2, (16 gauge) wire up to 25 Amps, but I feel safer using 12 or 14 gauge supply wire to the pump, taking into account the wire length of about 16 feet.
As far as a Lift Pump ground connection, I may use G302, LH Body Mount, or G403, Fuel Filler Ground, or any other ground screw, already mounted in the area.
As I said, I'm in the planning and ordering stage. Now I need to to decide on some type of adjustable lift pump, (minimal pressure > vacuum at load), and what type of hose, fittings, and bypass valve to use.
Sorry if this was too long, but I hope I didn't leave out any important details. Couldn't have done it without Helms.
If anyone else has the 2002 Helms Manuals, and has time to verify this info, this would ensure others that it is 100% accurate. Any ideas to improve this wiring are encouraged and appreciated.
Enough said,

[dmaxalliTech]

Modified, very impressed with your homework on this one. I havent checked it yet to see exactly how everything is coming togather but just wanted to throw in a few pennies of thought.

The fuel pump relay you mentioned in the UHFB is the relay for the gas engine fuel pump, they share the same fuse block. I think if you find the correct terminals your good to go.

The G304 ground on the drivers side body mount should be kept clean. I have found numerous times that the undercoating on the frame was still in place and not getting as good a contact as I would like to see, clean all well when removing ground, the ground is for the abs. It is also necc to install a nut on the backside of the bolt as the self tapper sometimes will not tighten up very good.

Good job with the research, I will get out the books and follow along and see how it works, I might do one that way for the factory appearence
Well done