EVIL ENERGY • TECHNICAL INSTALLATION GUIDE
EFI Fuel Cell Gas Tank Kit: Complete Installation, Plumbing & Troubleshooting Guide
Learn how the fuel cell, external fuel pump, 100-micron pre-filter, 10-micron post-filter, fuel pressure regulator and AN fuel lines work together in a return-style EFI fuel system. Follow the supplied kit manual and your vehicle service information for the actual installation.
Use this page as your installation walkthrough: the component list, mounting steps, exact plumbing sequence, fitting differences, pressure checks, and fault checks are provided below in one place. The official PDF is available as a supplementary reference—not required for understanding this article. Vehicle-specific electrical protection, vent design, mounting torque, and fuel-pressure targets must still be confirmed from the vehicle and component manufacturers.
Applies to: The EVIL ENERGY Fuel Cell Gas Tank Kit described in the supplied installation manual, for electronic fuel injection (EFI) systems only. Component quantities, hose materials and included fittings may differ between product configurations. Confirm vehicle-specific requirements, including mountings, venting and electrical protection, before installation.
Working with gasoline and pressurized fuel creates fire, explosion and injury hazards. Work in a ventilated area away from ignition sources; use approved fuel-handling equipment, eye protection and fuel-resistant gloves. Relieve fuel pressure and disconnect the negative battery cable as specified by the applicable service procedure before opening the system. Never start or drive a vehicle with a fuel leak. If you are not experienced with fuel-system work, have a qualified technician perform the installation.
1. Before Installing Your EFI Fuel System
Before removing existing components, verify that your build uses an EFI return-style configuration and that the selected fuel cell, pump, regulator, hose, filtration and mounting arrangements meet the vehicle's requirements. Confirm your vehicle fitment, required operating fuel pressure and electrical circuit specification before installation.
Pre-Installation Checklist
- Read the entire supplied kit installation guide and applicable vehicle service manual.
- Verify kit contents and inspect for cracked, dented, damaged or missing components.
- Check the intended fuel cell position and clearance from the exhaust, driveshaft, suspension and other moving parts.
- Identify the supply path, return path, fuel cell vent and the pump's inlet/outlet direction before routing hoses.
- Prepare a socket and wrench set, torque wrench, AN wrenches, hose cutter, deburring tool, drain pan, approved fuel transfer equipment, eye protection, fuel-resistant gloves and properly rated vehicle supports.
- Confirm that local laws and the vehicle's emissions and fuel-vapor requirements permit the intended installation.
Common mistake: Treating a universal-style kit as a complete vehicle-specific installation solution. Mounting hardware, wiring protection, venting, fuel-pressure requirements and fitting compatibility must still be checked for the actual build.
2. What's Included in the Fuel Cell Kit?
The guide's main package list identifies a fuel cell, external pump kit, adjustable regulator kit, two stages of filtration, hose and AN connections. Fuel cell capacity and hose construction depend on the selected kit option.
Fuel CellFuel storageView product ↗ 
External Fuel Pump300LPH product referenceView product ↗ 
100-Micron Pre-FilterSelect 100-micron variantView product ↗ 10-Micron Post-FilterSelect 10-micron variantView product ↗ 
Fuel Pressure RegulatorConfirm regulator configurationView product ↗ 
AN Hose & FittingsConfirm hose constructionView product ↗
Why use the coarser filter first?
A 100-micron pre-filter catches larger tank debris while allowing relatively free flow into the pump. Electric pumps are sensitive to inlet restriction: a fine filter before the pump can starve the inlet, cause cavitation-like noise and reduce fuel delivery.
Why place the finer filter afterward?
The pressurized side can support finer filtration to protect the fuel rail and injectors from small particles. Confirm that the filter's flow rating matches the pump and that its arrow points toward the engine.
| Component | Function | Manual-listed quantity |
|---|---|---|
| Fuel Cell | Fuel storage with supply/vent connections | 1 (capacity varies by configuration) |
| Fuel Pump Kit | Moves fuel from the cell toward the engine | 1 |
| Fuel Pressure Regulator Kit | Controls system pressure and return flow | 1 |
| 100-Micron Filter Kit | Pre-pump filtration | 1 |
| 10-Micron Filter Kit | Post-pump filtration | 1 |
| Fuel Hose | Supply/return plumbing; CPE, PTFE or antistatic PTFE as supplied | 1 hose set |
| 90-Degree AN Fitting | Hose-end routing | 4 |
| Straight AN Fitting | Hose-end routing | 8 |
| AN10 Female to AN6 Male Flare Reducer | Specified size transition | 2 |
Check your exact package: Kit contents vary by the selected product variant. Compare your order's variant and package list before installation. Explore the Fuel Cell Tank Kit and Upgraded Fuel Cell Tank Kit for configuration details.
Verify your kit: The official EVIL ENERGY installation guide (PDF) ↗, pages 4–5, lists kit components and sub-kit fitting quantities. Use the actual SKU and packed components to resolve differences between standard, upgraded, and other variants.
3. Understanding the Return-Style EFI Fuel System
This system uses a return-style EFI circuit. The 100-micron filter is positioned before the external pump; the 10-micron filter is positioned after it. Fuel moves through the fuel rail to the pressure regulator, and excess fuel returns to the fuel cell.
Fuel Pressure RegulatorAN6→AN10 ORB side adapterAN6→AN6 ORB return
Fuel Rail · EngineVerify rail port compatibility
10-Micron Post-FilterAN6 9/16-18 UNF fittingsVerify flow arrow
External Fuel PumpM18×1.5→AN6 inletM12×1.5→AN6 outlet
100-Micron Pre-FilterAN8 3/4-16 or AN10 7/8-14 inletAN6 9/16-18 outlet
Fuel Cell / Fuel TankSeparate supply and return ports
Match each component’s actual port markings, O-rings and fittings to the selected kit configuration before connecting the lines.
Follow the Connections in Order — Port by Port
| From → To | Hose / adapter shown in manual | Critical check |
|---|---|---|
| Fuel cell supply → 100 μm pre-filter | AN10 or AN8 supply hose; pre-filter inlet AN8 3/4-16 UNF or AN10 7/8-14 UNF fitting | Do not mistake the tank vent for the fuel supply outlet. Verify inlet seal and flow arrow. |
| 100 μm pre-filter → pump inlet | AN6 fuel hose; filter outlet AN6 9/16-18 UNF; pump inlet M18×1.5 to AN6 adapter | Keep this low-restriction run protected and free of kinks; confirm pump inlet orientation. |
| Pump outlet → 10 μm post-filter | Pump outlet M12×1.5 to AN6 adapter; AN6 fuel hose; filter inlet AN6 9/16-18 UNF | Do not swap pump inlet and outlet; filter arrow must follow fuel toward engine. |
| 10 μm post-filter → fuel rail inlet | AN6 hose and AN6 9/16-18 UNF filter fitting; vehicle-specific fuel rail connection | Fuel rail interface is not universal; verify actual rail thread / adapter separately. |
| Fuel rail outlet → regulator side port | AN6 hose; AN6 to AN10 ORB adapter with O-ring on the illustrated regulator | Plug only an unused regulator side port with specified AN10 plug + O-ring; not the return port. |
| Regulator return → fuel cell return | AN6 to AN6 ORB return fitting; AN6 return hose | Keep return path open and correctly routed. A restriction may drive fuel pressure high. |
Port note: Diagram follows the supplied return-style kit manual. Confirm that the fuel rail ports and adapters match your engine configuration. Check actual component port threads, fittings, and flow-direction markings before installation.
Why Are Two Fuel Filters Used?
100-micron pre-filter: Install this filter between the fuel cell and the fuel pump. Confirm the arrow matches the direction of fuel travel.
10-micron post-filter: Install this filter between the fuel pump and fuel rail. Its flow-direction arrow must also point in the correct direction.
Return line: Connect the regulator's return port to the fuel cell's designated return port as shown in the specific kit diagram. Do not confuse the regulator return port with an unused side port, which may have a dedicated plug and O-ring in the supplied configuration.
For additional component details, see the EVIL ENERGY 100-Micron Inline Fuel Filter. Verify the correct filter model, port size and bracket before substituting a component.
What happens if I connect the return line to the wrong port?
The regulator needs the intended return path back to the fuel cell. An obstructed or misrouted return can cause excessive pressure. The manual permits plugging an unused regulator side port with its supplied AN10 plug and O-ring; it does not permit capping the AN6 return port in this layout.
What if a filter arrow points the wrong way?
Flow may be restricted or the internal element may not operate as intended. The manual specifically requires checking flow arrows before mounting both filters. Correct orientation before priming; if the system was run incorrectly, inspect filter condition and retest pressure.
Inspect the pre-filter, fuel supply restrictions, venting, pump position, and electrical connections before replacing the pump. A noisy pump does not necessarily indicate a failed pump.
Technical reading: · · EVIL ENERGY circuit diagram (manual page 11) ↗
4. Removing Existing Fuel System Components
Follow the vehicle manufacturer's service procedure to depressurize the existing system before loosening any connection. The supplied guide describes locating and removing the pump fuse, running the engine until it stalls, switching ignition off, allowing the engine to cool and disconnecting the negative battery cable. This sequence must be reconciled with the vehicle-specific instructions.
- Relieve fuel pressure: Use the applicable service procedure and verify that the system is safe to open.
- Remove the old filter: Position an approved collection container below it, loosen the connections and remove the filter.
- Remove the old pump: Disconnect fuel and electrical connections, then remove its mounting hardware.
- Remove the old regulator: Access the unit, disconnect the reference hose if fitted, protect the area against fuel spillage, and remove the regulator and connections.
Safety check: Support the vehicle on suitable jack stands when working below it; never rely on a hydraulic jack alone.
5. Step-by-Step Fuel System Installation
Follow the six stages below in sequence. Each card includes the component photo, the installation action, and the final inspection point. Product images are representative; port locations and fitment can vary by selected configuration.
Step 1: Install the Fuel Cell
Select a mounting location with adequate clearance from exhaust components, the driveshaft, suspension and moving parts. Secure the cell with suitable mounting hardware and confirm that the mounting position permits protected supply, return and vent routing. The manual identifies the fuel outlet and vent outlet separately; do not assume these ports are interchangeable.
Before moving on: Check that the tank is secure and that the vehicle-specific fuel-vapor/venting arrangement has been evaluated. The manual does not provide a complete vehicle-specific vent or rollover-valve design.
The fuel outlet feeds the 100-micron pre-filter. The vent outlet is for the required tank venting arrangement—not the return hose. Identify the separate return connection on the actual fuel cell before routing the regulator return line. Never assume the port positions are interchangeable.
Step 2: Install the External Fuel Pump
Mount the pump near the fuel cell, preferably at or below the bottom of the cell, as stated in the guide. Keep it away from exhaust heat, road debris and moving components. Install the supplied vibration isolators where applicable, identify the indicated inlet and outlet, and secure the pump and bracket.
The pump's electrical connections must be completed using an appropriately engineered vehicle-specific circuit. Connect the pump terminals according to the marked positive (+) and negative (−) polarity. Select fuse protection, relay and wire size for the specific pump circuit and vehicle electrical system.
Component reference: EVIL ENERGY 300LPH External Inline Fuel Pump Kit.
Fuel enters at the marked inlet (M18×1.5 to AN6 adapter in this kit) and leaves at the marked outlet (M12×1.5 to AN6). The terminals are marked positive (+) and negative (−); connect only to a vehicle-appropriate protected circuit. Reversed plumbing may prevent correct fuel delivery. Incorrect wiring risks malfunction or damage: stop and verify the terminal markings before power is applied.
Step 3: Mount the 100-Micron and 10-Micron Filters
Secure each filter with its designated bracket and inspect the fuel-flow arrow. In the manual's layout, the 100-micron filter sits before the pump and the 10-micron filter sits after it. Confirm the fittings and filter bodies are suitable for the actual hose and pressure requirements.
The 100-micron pre-filter goes between the fuel cell and pump; the 10-micron post-filter goes between the pump and rail. Each filter arrow must point in the actual fuel-flow direction. A reversed filter can restrict delivery or impair filtration. Swapping the coarse and fine filter positions can increase pump inlet restriction or leave the injectors less protected.
Step 4: Install the Fuel Pressure Regulator
Mount the regulator away from the exhaust manifold and other high-temperature surfaces. Fit the pressure gauge in the designated 1/8-inch NPT gauge port using a suitable sealant for that NPT connection. Identify the regulator's side ports, return port and 5/32-inch vacuum/boost reference port before connecting the system.
Where the approved configuration uses vacuum/boost reference, connect it as specified. Where no reference is used, the provided manual instructs the installer to leave that reference port open to atmosphere—not plugged. Confirm that this instruction matches the supplied regulator model.
The 1/8-inch NPT gauge port accepts the pressure gauge, with suitable NPT thread sealant. The 5/32-inch vacuum/boost reference port connects to a reference line when applicable; for the supplied configuration, leave it open to atmosphere if no reference is used. The ORB-10 side ports carry fuel and the ORB-06 return port goes back to the fuel cell. Do not cap the return port. AN and ORB sealing surfaces do not take PTFE tape.
Step 5: Build and Route the Fuel Lines
Plan routes with allowance for bends, suspension movement and service access. Keep lines away from exhaust heat, abrasion points, sharp edges and rotating parts. Confirm the hose type before assembling any AN hose ends: CPE and PTFE require different assembly methods.
Step 6: Connect the Complete System
Connect the components in the documented order: fuel cell → 100-micron filter → pump → 10-micron filter → fuel rail → regulator → return line → fuel cell. Connect the fuel rail outlet to the regulator side port using the corresponding hose and adapter. Where a regulator side port is unused, install the AN10 port plug with its O-ring; this does not mean the regulator's return port should be capped.
Recheck that every hose is seated, supported, free of kinks and not under tension. Confirm that all installed fittings match the relevant threads and sealing interfaces.
Component port illustrations are available in the EVIL ENERGY manual (PDF pages 8–11) ↗. This webpage includes the installation order and port-to-port connection table so you can follow it without opening another document.
6. How to Assemble CPE and PTFE Fuel Lines
Hose-end assembly is one of the most error-prone parts of a custom fuel installation. The correct technique depends on whether the kit contains CPE or PTFE hose. Never assume the hose ends are interchangeable between constructions.
Prepare and Cut the Hose
- Measure the intended route and allow room for bends.
- Wrap the intended cut point with tape, cut the hose square and remove any burrs.
- Clean loose debris from the cut end before installing the fitting.
For CPE Fuel Hose
Secure the hose socket in a vise, thread the hose into the socket until snug and leave the manual-specified 1–1.5 mm gap. Mark the hose position so movement can be detected during assembly.
For PTFE Fuel Hose
Slide the socket over the hose, carefully separate the outer braid and position the ferrule over the PTFE liner. Seat the ferrule completely against the PTFE liner without a gap, then push the hose assembly fully onto the nipple. Continue with the fitting manufacturer's compatible assembly procedure.
Complete and Check the Hose Assembly
Apply appropriate assembly lubricant to fitting threads as directed, hold the socket and tighten the fitting assembly to its specified seated position. Clean and pressure-test the finished hose assembly before it is installed on the vehicle.
Use thread sealant only on applicable NPT threads. Do not apply PTFE tape or thread sealant to AN flare or ORB O-ring sealing surfaces. Do not overtighten AN fittings.
Need additional line length or routing options? Review EVIL ENERGY PTFE Fuel Hose. Select compatible hose ends based on the actual hose size, construction and port interfaces; a matching AN size alone does not guarantee assembly compatibility.
If a Braided PTFE Line Becomes Wet at the Fitting
Stop the pump and do not start the engine. Fuel visible at the braid, ferrule, or hose end means the line has not passed the leak check. Do not respond simply by adding thread tape or forcefully tightening an assembled fitting.
- After shutting down and safely depressurizing the system, identify the exact wet location and inspect the hose and fitting.
- Confirm the fitting is specifically compatible with the supplied PTFE hose construction and outer diameter; “6AN” alone is not proof of a compatible hose end.
- Inspect the PTFE liner for cracking, deformation, an uneven cut, or damage from an incorrectly positioned ferrule.
- Confirm the ferrule is fully seated against the liner and that the hose has not backed out during assembly. Follow the supplied fitting's approved reuse/replacement policy.
- If the hose or fitting is damaged or cannot be confidently assembled, replace it with a matched component. Pressure-test the assembly by the manufacturer-approved method before installation.
Three Common Hose-End Mistakes
CPE and PTFE assemblies use different structures. Never mix fitting types without verified product specifications.
A rough cut, displaced ferrule, or liner deformation can prevent sealing and allow fuel to reach the braid.
AN flare and ORB O-ring interfaces do not seal by thread tape. Identify the actual sealing surface instead.
AN flare, ORB O-ring and NPT threaded joints achieve sealing differently. Avoid treating leakage as a problem that can always be solved with extra tape or tightening force. Identify the sealing interface, compatible hose end and intact sealing components first.
Parker O-Ring Handbook — Boss Seal Tables ↗ (ORB reference dimensions) · EVIL ENERGY Hose Assembly Drawings (PDF page 10) ↗
7. Fuel System Priming, Pressure Testing and Adjustment
Do not run the pump without fuel. The manual calls for filling the fuel cell with clean fuel before priming the system, then checking the pressure gauge with ignition on and engine off. Follow the specific vehicle's electrical and priming procedure.
Pre-Start Inspection
- Confirm sufficient clean fuel in the cell and that the pump will not run dry.
- Restore the pump fuse and negative battery connection as instructed, with ignition off before reinstallation.
- Prime the system without starting the engine, checking that the gauge registers pressure.
- Inspect the cell, pump, both filters, regulator, every hose and every fitting for leaks.
- If a leak is found, switch ignition off, address the spill and repair the cause before retesting.
Pressure Adjustment and Follow-Up
Only after successful initial checks should the engine be started and the regulator adjusted to the vehicle/EFI-system-required fuel pressure. Turn the regulator adjustment clockwise to increase fuel pressure or counterclockwise to decrease it. Always monitor a connected gauge, then lock the adjustment using the jam nut.
Inspect for leaks again after warm-up and after the first road test. The manual also calls for a further inspection after 50–100 km and periodic checks thereafter. Never continue operating a vehicle with a known fuel leak.
Do not use a universal pressure figure: The manual does not specify one fuel-pressure target for every engine, controller or regulator spring configuration.
8. Common EFI Fuel System Problems and Solutions
If the system does not operate correctly, stop and identify the symptom before replacing parts. The following checks are adapted from the troubleshooting table in the supplied kit guide.
| Symptom | Possible cause | Initial inspection |
|---|---|---|
| Engine won't start | Pump not running, insufficient pressure, incorrect routing | Check pump power, fuse and ground, gauge reading, filter condition and the approved flow diagram. |
| Low fuel pressure | Leak, reversed or clogged filter, regulator setting | Inspect for leaks, confirm filter arrows and condition, verify the required regulator setting. |
| High fuel pressure | Incorrect regulator adjustment, restricted return | Check measured pressure and examine the return line for kinks, blockage or incorrect routing. |
| Fuel leak | Loose connection, damaged hose/fitting | Shut down immediately. Repair or replace the affected part and retest before operation. |
| Noisy fuel pump | Incorrect mounting or restricted inlet | Inspect pump position, vibration isolators, pre-filter condition and supply path. |
| Fluctuating pressure | Air entering system, incorrect reference connection | Inspect all connections and verify regulator vacuum/boost reference routing where used. |
Installation mistake to avoid: Do not treat a pressure drop after pump shutdown as conclusive evidence of a faulty regulator. This regulator may not retain residual pressure after the pump stops; assess the system using the correct operating test procedure.
9. Frequently Asked Questions
Q: Is this fuel cell kit designed for carbureted engines?
Q: Should the 100-micron fuel filter go before or after the fuel pump?
Q: Can I cap the fuel pressure regulator return port?
Q: Do AN fuel fittings need PTFE tape?
Q: How do I know which fuel-pressure setting is correct?
Q: What should I check if the external fuel pump is unusually loud?
Q: Can I use a different hose or AN fitting?
Q: How is the fuel cell vent connected?
Q: When should I inspect the system again after installation?
Q: Why are the 100-micron and 10-micron filters not interchangeable?
Q: What happens if I install a fuel filter backward?
Q: Can a fuel hose leak even if the fitting feels tight?
Q: Can I plug the fuel-pressure regulator return port?
Q: Which fuel rail should I use with this kit?
Q: Does the fuel-cell vent connect to the fuel return line?
10. Explore Related EVIL ENERGY Fuel System Components
The links below are references for selecting or replacing components. Always check your exact kit configuration before purchasing additional parts; items shown may already be included in your bundle.
11. Technical References & Installation Documentation
This guide is based on the supplied EVIL ENERGY kit instructions. Additional sources below explain industry practices; they do not replace the instructions for this specific product or vehicle.
Final Installation Reminder
A complete EFI fuel system depends on correct component selection, safe mounting, compatible fittings, reliable electrical connections, correct fuel-line routing and thorough leak testing. Use the full EVIL ENERGY installation manual alongside the vehicle's service instructions, and seek professional assistance when a step exceeds your experience.
Need help with your installation? If you have questions about product compatibility, component selection, installation procedures or troubleshooting, our support team is here to help. Call us at +1 (866) 850-9888 or email support@ievilenergy.com for assistance.
Before starting the engine, double-check all connections and verify that the entire fuel system is free of leaks. Always follow applicable safety procedures and vehicle manufacturer recommendations to help ensure reliable operation and safe performance.
