Secondary fuel pump activation harness full kit with main relay harness, 13 psi pressure switch, trigger harnesses, pump power lead and test plug
Main harness with normally open relay, weatherproof quick connect and battery ring terminal in braided sleeving
Fuel pump power harness with 30A quick connect and two M6 ring terminals
13 psi boost referenced pressure switch (Hobbs switch) with 1/8 inch NPT brass thread and weatherproof connector
Positive trigger harness with quick connect and lead for a switched 12V source
Negative trigger harness linking the pressure switch or a fuel pump controller to the main harness
Test plug jumper that forces the secondary fuel pump on for setting fuel pressure and troubleshooting
Secondary fuel pump activation harness full kit with main relay harness, 13 psi pressure switch, trigger harnesses, pump power lead and test plug
Main harness with normally open relay, weatherproof quick connect and battery ring terminal in braided sleeving
Fuel pump power harness with 30A quick connect and two M6 ring terminals
13 psi boost referenced pressure switch (Hobbs switch) with 1/8 inch NPT brass thread and weatherproof connector
Positive trigger harness with quick connect and lead for a switched 12V source
Negative trigger harness linking the pressure switch or a fuel pump controller to the main harness
Test plug jumper that forces the secondary fuel pump on for setting fuel pressure and troubleshooting

Secondary Fuel Pump Activation Harness - BMW & Universal

OneFastShop SKU: OFSPAH
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This harness turns a secondary fuel pump on and off through a normally open relay, so the trigger source never carries pump current. It can be triggered by the included 13 psi boost referenced pressure switch, a negative trigger output from a controller such as the Motiv ReFlex+ or a bootmod3 REV2 board, or a switched 12V source. The main harness has a pre-installed 30A fuse and 10 AWG oxygen free copper power wire, and the pump harness connects with a 30A quick connect and two M6 ring terminals. With the included pressure switch, installation needs no cutting, stripping or crimping.

Specifications

Type Secondary fuel pump activation harness
Pumps Controlled One 12V secondary fuel pump
Compatible Pumps 12V brushed pumps run on/off, such as the Walbro 450 (F90000274); not for brushless pumps that need their own speed controller
Trigger Negative trigger (switch to ground) or positive trigger (switched 12V)
Activation Pressure 13 psi with the included pressure switch, pre-set
Pressure Switch Thread 1/8" NPT
Relay Standard normally open on/off relay with mounting tab; 0% or 100% duty only, not PWM capable
Fuse 30A, pre-installed at the battery end
Power Wire 10 AWG oxygen free copper
Pump Connection 30A quick connect pump harness with 2x M6 ring terminals; fuel compatible wire for in-tank routing through a bulkhead
Connectors Weatherproof quick connects
Wiring Options
  • Pressure switch (included): plugs into the negative trigger harness; the pump runs above 13 psi of boost
  • Motiv ReFlex+: green wire to AUX 3 or AUX 4, 20 Hz output, table at 0 below 13 psi and 100 above
  • bootmod3 REV2 (S58, B58 with CustomROM V2): brown to REV2 positive, green to REV2 pulsed ground on the LPFP output; not available on the N54
  • Pro EFI and other controllers: any output that switches to ground at 0% or 100% duty wires like the ReFlex+
  • Switched 12V: positive trigger harness to an ignition switched fuse tap; the pump runs whenever the ignition is on
Install
  • Fused lead to battery positive; ground to the battery or bare chassis metal
  • Pressure switch threads into a 1/8" NPT port or tee in a line that sees intake manifold pressure, away from turbo heat
  • Relay runs on/off only; a PWM output will make it buzz and fail
  • On E chassis BMWs, do not trigger from the factory pump wire, since the EKP pulses it
  • Test plug is for setting fuel pressure and troubleshooting only, not for driving
What's in the Box
  • Main harness with pre-installed 30A fuse and relay
  • 13 psi pressure switch (Hobbs switch)
  • Negative trigger harness
  • Positive trigger harness
  • Fuel pump power harness
  • Test plug
Fuel pump, boost line tee and hose not included
Fitment Notes Universal: works with any 12V secondary fuel pump on any make. Common on BMW N54, N55, N20, S55, B58 and S58 dual pump LPFP builds, and included with every OneFastShop Stage 3 and Stage 3.5 dual pump LPFP kit
Quantity 1
Warranty 1 year (12 months) from delivery; tuning does not void it

Documents: Installation Diagram (PDF) | Secondary Fuel Pump Wiring Guide

Which wire goes to the Motiv ReFlex+?

  • Cut the negative trigger harness about 2 inches behind the connector, tape or trim the brown wire, and splice the green wire to AUX 3 (pin 18) or AUX 4 (pin 19). In TunerPro RT, set the auxiliary frequency to 20 Hz and fill the table with 0 below 13 psi and 100 at 13 psi and above.

Does bootmod3 support this harness on the N54?

  • No. The bootmod3 REV2 board works on the S58 and B58 with CustomROM V2. On the N54, use the included pressure switch or a ReFlex+ output.

How do I test the secondary pump after install?

  • With the engine off, unplug the pressure switch and bridge its two harness pins, or use the included test plug. The relay should click and the pump should run.

Why does my relay buzz?

  • The controller output is pulsing. The relay is on/off only, so set the output table to 0 and 100 only; PWM will make the relay fail.

What fuel pressure should I see once it is installed?

  • On a BMW, low side pressure should hold near 72 psi (5 bar) as boost passes 13 psi. A drop above 13 psi means the secondary pump is not engaging or the primary pump has a fault.

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Returns

  • 30 days from delivery to request and ship back a return on new, uninstalled items in original packaging with all hardware.
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A
Anonymous
Used it on my 2009

Used it on my 2009 335i

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