Tech Tips: Fuel System Series

Lethal Performance Tech Tips | Fuel System Series


With any build, whether you’re gunning for 600rwhp or 1500rwhp, you’re gonna need fuel.


Here at Lethal Performance, we offer fuel system options for just about every level of horsepower, from the budget build to 2000rwhp builds. You can purchase the systems complete with everything needed to install, but it’s important to understand the components of the system for installation & purpose. That’s where our latest Tech Tips series comes in!


With each episode, Jared will go over the components that come in our fuel systems, from the budget kits which use the factory feed line & fuel rails to the complete systems that come with everything from rails to pumps. Be sure to bookmark this page, as we will add each episode below as they are released.



Episode 1: The Lethal Performance Return Style Harness



When converting your factory returnless setup to return style, wiring is key. Fortunately, we’ve made it easy! Our dual & triple return style harnesses are included in every Lethal Performance / divisionX fuel system but did you know they can also be used in just about any other return style setup? You can simply cut the fuel hat connector off of the end of the harness and splice the harness to your own fuel hat wiring. #nowyouknow


Our return style harness has multiple components: 

  • Fusible link
  • Relays
  • Ground wires
  • Trigger wire
  • Fuse holders
  • OEM style connector


Let's start with the included fusible link.



These are included with every harness. The link will connect to the positive terminal on your battery box. The 10g wires will then connect to the long 10g power wires of the harness that lead to the relays.



Each harness will include 2 or 3 relays, depending on which harness you order. These will control the pumps. The relays are powered via the fusible link and have attached black wires which are the grounds. You will need to ground these to an appropriate spot on the vehicle.



Also attached to the relays is a blue wire. This is the trigger wire that will tell the pumps to work. It can be wired in 2 different ways, either as a ‘key on’ setup or to prime like the factory pump(s).


After the relays you will find 2 (or 3) fuse holders wired in, each containing a 20amp fuse.



These fuses protect the relays if there is a short between the pumps and the relays. The fuses can also be upgraded to a larger amperage should you need it for larger pumps.


The last section of the harness is a loomed section coming from the fuse holders which leads down to the OEM style 6-pin connector. This connector will plug directly into the divisionX Gen 3 SN95 fuel hat OR you can cut the connector off and wire the harness directly to your own fuel hat setup. We will cover more of the connection options when we discuss the fuel hats in future episodes.

Episode 2: The divisionX SN95 Fuel Pump Hat



In episode 2 of our Fuel System Series, Jared goes over the basics of the divisionX fuel pump hat for the 99-04 Mustang.



We use these fuel pump hats in all of our Lethal Performance and divisionX fuel systems for the 99-04 GT, Mach 1 and Cobra models. We offer systems ranging from the Budget & Budget Plus kits to the full 1400+rwhp fuel systems. This hat is a direct replacement for your factory fuel hat setup, making it super easy to convert to a return style system and support tons of horsepower without worrying about sumps, external pumps, etc.


NOTE: This hat will work in the GT and Mach 1 factory tanks, however you will need to remove the plastic basket at the bottom of the tank that supported the factory fuel pump setup. Also to note, the 03-04 Cobra fuel tanks have a superior baffle system which helps to eliminate fuel starvation due to fuel slosh. If you have a GT or Mach 1 you can choose to upgrade to the Glenns Performance 03 Cobra style fuel tank (CLICK HERE).


Let’s break down the essential pieces to the hat:

  • OEM-style 6-pin connector
  • Feed & Return Ports
  • OEM Level Sender attachment
  • Fuel pump connectors & wiring
  • Fuel pump basket


The divisionX fuel hat has one prominent feature not found elsewhere: the OEM-style 6-pin connector on top. What’s the mean? Not only is it a leak-proof design, but it also gives you a plug & play wiring option using either our Lethal Performance Return Style Harness (discussed in Episode 1) or, if you want to use your own wiring, our 6-pin pigtail (SKU: DX-0045).

If you choose to use our Lethal harness (or if you purchase a complete fuel system that comes with the harness), the system will be plug & play. The harness plugs directly into the connector at the top of the hat. There will be 2 loose wires for the level sender that get wired to your factory harness.



To access the level sender wires in your factory harness, simply cut the connections and peel back the wire loom to reveal the OEM wires. There will be 4 wires, 2 small and 2 large. The 2 small wires will be your level sender wires. You will connect the yellow wire to yellow wire and black wire to black wire (however, these wires are run by ohms and not done by positive/negative so you could cross them and the sender will still work properly).

NOTE: Sometimes, the level sender will need to re-learn. If your fuel level is not reading properly, give the car some time/miles to adapt.


If you are using your own wiring, you can purchase the divisionX pigtail (CLICK HERE). This pigtail has the same connector as our Lethal harness to plug directly into the fuel hat, but allows you to wire in your own setup, including the same level sender wires.



The divisionX SN95 fuel hat will come with the feed & return fittings already installed. The feed fitting supplied is a 10an O-ring and the return port has an 8an O-ring. These fittings can easily be swapped out to accommodate different sized lines.


On the underside of the SN95 fuel hat, we’ll start with the spine of the hat. This is where you can attach your OEM level sender. The fuel hat accepts the 03-04 Cobra level sender with no bracket needed. If you have a 99-04 GT/Mach 1 or a 99-01 Cobra, you can purchase the divisionX level sender bracket (DX-37011) and use your OEM level sender.



There are also 2 wires on the underside of the hat for wiring up the level sender—one with a spade connector and one with a terminal. The terminal will be grounded to the spine of the fuel hat while the spade connector will connect to the spade connector on your factory level sender.



Also on the underside of the hat you will find the fuel pump connectors which allow plug & play use of most fuel pumps.


The bottommost part of the fuel hat is the fuel pump basket, equipped with o-rings for seating of the fuel pumps. The divisionX fuel pump hat accommodates the most popular fuel pump choices from both Walbro and Aeromotive.


Here are the pumps you can use in the SN95 fuel hat:

  • Walbro 255lph (SKU: WAL-GSS342)
  • Aeromotive Stealth 340lph (AER-11542)
  • Walbro 400lph (SKU: WAL-F90000267)
  • Walbro 465lph (SKU: WAL-F90000267)
  • Walbro 465lph High Pressure (SKU: WAL-F90000274)
  • Walbro 485lph (SKU: WAL-F90000285)


Check out the fuel chart below for their flow rates & E85 compatibility:



IMPORTANT: When installing the fuel pumps, you will want to make sure that they are positioned so that the bottom of the fuel filter sock is 1.75”-1.87” from the bottom of the fuel hat basket. This will insure that you have the proper placement for fuel pickup.



CLICK HERE for the full instructions on the divisionX SN95 fuel pump hat.

Episode 3: divisionX S197C Fuel Hat



In this week’s episode, Jared covers the S197C divisionX fuel hat.  This hat will work in the 2011-up Mustang GT and the 2013-14 GT500. Similar to the SN95 fuel hat we featured in last week’s episode, this fuel hat is a direct replacement for your factory fuel hat setup when converting to a return style fuel system. 



We have used these hats on MANY of our #teamlethal projects including our 2011 Mustang GT, 2012 Boss 302, 2013 Shelby GT500 and even now on our 2018 Mustang GT. We include the divisionX triple pump fuel hat in all of our complete fuel systems for the 2011-up Mustang GT as well as the 2013-14 Shelby GT500s. Let’s take a closer look at the hat.

We’ll start at the bottom of the hat. Like the other divisionX fuel hats, there is a basket for the pumps to be mounted in. This fuel hat houses up to 3 fuel pumps and has plug & play connections for most pumps as well. 




Here is a list of compatible fuel pumps:

  • Walbro 255lph (SKU: WAL-GSS342)
  • Aeromotive Stealth 340lph (AER-11542)
  • Walbro 400lph (SKU: WAL-F90000267)
  • Walbro 465lph (SKU: WAL-F90000267)
  • Walbro 465lph High Pressure (SKU: WAL-F90000274)
  • Walbro 485lph (SKU: WAL-F90000285)


For a list of flow rates, check out the chart below:


Also located on the underside of the hat are the 2 wires to wire up your level sender. You are able to mount your OEM level sender to the spine of the hat & read fuel levels just like stock.



Moving up to the top of the hat! The hat will not come equipped with the fittings however there is 2 ports: a 10an feed and an 8an return.



You can use any o-ring fittings in here to adapt to your fuel hose size. For example if your return is a 6an hose, you can use a 6an to 8an o-ring fitting. If your feed is a 10an then you just need a 10an to 10an o-ring fitting. 

CLICK HERE to see the O-ring fittings. If you don't see the size you need, give us a shout. 

Also located on the top of the hat is all of the wiring to connect to your harness & level sender connections. 



Unlike the 99-04 Fuel hat, this hat requires you to do some splicing & connecting of wires. If you are using your own wiring, you can connect the wires directly. There are 3 power and 3 ground wires, as well as 2 yellow wires which will connect to your OEM level sender wires. These are done by ohms so no need to worry about which wire connects to which, they are not polarized. 

If you are using our Lethal Performance Triple Pump Return Harness, we have drastically improved the way the hat & harness connect. Previously, our harness did not come with the OEM-style connector and required you to splice the harness directly to the wires on the hat. While this isn’t a huge ordeal, if you ever needed to remove the fuel hat for maintenance (change the pumps, etc) then you would need to cut the connections and redo them once the hat was re-installed. However, that has changed.  We now have added the 6-pin connector to the end of our harness and include it’s matching pigtail.



You will wire the pigtail directly to the wires on the fuel hat and then plug it into the connector on our triple pump harness. This allows for a clean installation and also, whenever you need to remove the fuel hat later on you can simply disconnect at the harness. No need for cutting or splicing later on. 

If you’d like to purchase this fuel hat, CLICK HERE.


Episode 4: P.T.F.E. vs Push-Lite Fuel Hose



When you go to buy a fuel system on our site, one of the drop down options is to choose the type of fuel hose you would like the system to come with.

There are 2 options:

  • Standard Pre-assembled Fragola PTFE Hose


  • Fragola Push-Lite Race Hose and Fittings


We are often asked what the difference is between the hoses and if one is better than the other. In Episode 4 of our Fuel System Series, Jared discusses the answer to those questions!


Let’s start with the Push-Lite Hose, aka push lock. This hose consists of an inner layer of synthetic PKR covered with a fiber braid reinforcement and wrapped with a weather-resistant textile cover. It is very flexible and comes in sizes from 4an to 12an.



The fittings used are a simple barb fitting that is pushed onto the end of the hose (hence the name) and can be further strengthened using Fragola clamps (click here for the clamps). 

Check out this (super old) video of [baby] Jared installing a Push-Lite hose end onto the hose:



We have used this hose in many of our project vehicles, but when E85 started hitting the market we noticed that the fuel would permeate the hose and create a fuel smell (fuel weep!). We weren’t happy with this (and neither were our customers) so we reached out to Fragola for a new alternative. They obliged with their PTFE series of fuel hose.

The properties of P.T.F.E. make it a natural for all highly corrosive applications like E85 and other ethanol fuels. The hose will take high pressure and cycle over and over without failure.



P.T.F.E. powder is extruded into a smooth bore tube product. The tube is then fed into a machine that weaves stainless wire into the familiar braided pattern. The hose is then coated with a protective black coating that not only functions as a barrier but also looks super clean. 



Unlike the push lock setups, all of our fuel systems ordered with PTFE hose will come pre-assembled with the fittings installed. We have diagrams outlining the placement of the hoses on our Installation Instructions pages for the systems (click here), making it easier for you.



NOTE: Our 99-04 Budget systems will come with 1 fitting not installed (pictured above), as each car & setup will require the line to be a different length. However, you can install the fitting yourself with basic tools & some elbow grease. 

If you have any further questions on which fuel hose is best for you, give us a call and we'll be happy to help.


Episode 5: SN95 Fuel Hat FAQ Install Questions



We continue our Fuel System Series of Tech Tips videos this week with a video on some commonly asked questions about the installation process of the divisionX SN95 Fuel Hat into your 99-04 Mustang. 


The first question discussed is where to cut your factory fuel hat wiring. If you cut the wiring in the wrong place, it will lead to issues down the road with installation as you will be cutting wires vital to other components of the car's fuel system. 

You will want to cut your factory wiring just a few inches from the OEM fuel hat, before it meets up with the harness. See image below.



By cutting here, you retain wiring to the other parts of the setup. 


After you have cut it, you will see two small black and yellow wires. Once you connect the Lethal Performance Return Style Harness to the divisionX hat, you will have two small black and yellow wires. You will splice these together with the small wires from the factory harness to control your fuel level sender. 


The 2nd part of the video covers installation of the fuel pumps into the basket of the fuel hat. This part will depend on what type of fuel pump you are using. Does your pump have a bell shape? Here's what a bell shaped pump looks like:



If you are using a smooth Walbro pump with no bell like a GSS342, you will need to install the pump into the basket so that it measures 1.75"-1.87" from the bottom of the basket to the bottom of the fuel sock. See image below.



If you are using a Walbro 465lph or similar pump with a bell, you will need to trim the submersible hose on the underside of the hat and slide the pump all of the way up until the bell reaches the basket. 



Proper pump alignment is a crucial step to insure you will not either starve the pump or crush the sock and block the inlet. 



If you have any questions, please feel free to give us a shout. Stay tuned for future episodes of our Fuel System Series where we’ll go over more components of the return style fuel system.