Fuel System Plumbing Guide

Fuel System Plumbing Guide - Professional Installation

Complete guide for planning and installing high-performance fuel systems using AN fittings and braided hose.

Before You Start - Planning Checklist

System Requirements

  • Fuel type (petrol, E85, methanol, diesel)
  • Engine power output (determines line size)
  • Fuel delivery type (EFI, carbureted, return/returnless)
  • Fuel pump type and flow rate
  • Tank location and capacity

Safety Requirements

  • ⚠️ Work in well-ventilated area
  • ⚠️ No open flames or sparks
  • ⚠️ Fire extinguisher nearby
  • ⚠️ Disconnect battery before starting
  • ⚠️ Drain fuel system completely

Fuel Line Sizing Guide

Recommended AN Sizes by Power Output

Carbureted Systems:

  • Up to 300 HP: -6AN feed line
  • 300-500 HP: -8AN feed line
  • 500-750 HP: -10AN feed line
  • 750-1000 HP: -12AN feed line
  • 1000+ HP: Dual -8AN or single -12AN/-16AN

EFI Systems (with return line):

  • Up to 400 HP: -6AN feed, -6AN return
  • 400-600 HP: -8AN feed, -6AN return
  • 600-800 HP: -10AN feed, -8AN return
  • 800-1200 HP: -12AN feed, -10AN return
  • 1200+ HP: -12AN/-16AN feed, -10AN return

Returnless EFI:

  • Same as carbureted sizing (no return line needed)

Component Selection

Hose & Fittings

Fuel System Components

Installation Steps

Step 1: Plan Your Routing

  1. Measure distances from tank to pump to engine
  2. Plan routing away from heat sources (minimum 50mm from exhaust)
  3. Avoid sharp bends (minimum 3x hose diameter bend radius)
  4. Plan mounting points for pump, filter, and regulator
  5. Consider serviceability and future maintenance

Step 2: Install Tank Fittings

  1. Drain and clean fuel tank completely
  2. Mark locations for feed, return, and vent bungs
  3. Drill holes to correct size (see weld bung guide)
  4. Weld bungs in place (see weld bung installation guide)
  5. Pressure test tank before final installation

Step 3: Mount Components

  1. Mount fuel pump (below tank level if possible)
  2. Mount fuel filter (before pump for carb, after pump for EFI)
  3. Mount fuel pressure regulator (close to fuel rail for EFI)
  4. Ensure all components are securely mounted
  5. Check clearance from heat and moving parts

Step 4: Assemble Hoses

  1. Cut hoses to length (add extra for bends)
  2. Install hose ends (see installation guides for your series)
  3. Label hoses (feed, return, vent) before installation
  4. Double-check all connections are tight

Step 5: Route and Connect Lines

  1. Start from tank and work toward engine
  2. Use hose separators every 300-400mm
  3. Maintain proper bend radius throughout
  4. Keep lines away from heat sources
  5. Connect to fuel rail or carburetor
  6. Install return line (if applicable)

Step 6: Pressure Test

  1. Verify all connections are tight
  2. Reconnect battery
  3. Turn ignition on (don't start engine)
  4. Check fuel pressure at regulator
  5. Inspect all connections for leaks
  6. Wipe connections and check again after 5 minutes

Step 7: Final Checks

  1. Start engine and check for leaks under running conditions
  2. Verify fuel pressure is correct
  3. Check for adequate fuel flow
  4. Inspect all hose routing for clearance
  5. Secure any loose hoses with additional separators

Fuel Pressure Specifications

Carbureted Systems

  • Standard carburetor: 5-7 PSI
  • High-performance carburetor: 6-9 PSI
  • Alcohol fuel: 8-12 PSI

EFI Systems

  • Throttle body injection: 10-15 PSI
  • Port injection (naturally aspirated): 40-45 PSI
  • Port injection (boosted): 43 PSI base + boost pressure
  • Direct injection: 500-2000+ PSI (requires special pump)

Safety Guidelines

Critical Safety Rules

  • ⚠️ Never work on fuel system with engine running
  • ⚠️ Always disconnect battery before starting work
  • ⚠️ Drain fuel system completely before modifications
  • ⚠️ Work in well-ventilated area only
  • ⚠️ No smoking, sparks, or open flames
  • ⚠️ Have fire extinguisher ready
  • ⚠️ Wear safety glasses and gloves

Fuel Type Considerations

E85 Ethanol:

  • Requires E85-compatible hose and fittings
  • Higher flow rate needed (30% more than petrol)
  • Check all components are ethanol-safe

Methanol:

  • Requires methanol-compatible materials
  • Significantly higher flow rate needed (2x petrol)
  • More corrosive - inspect regularly

Diesel:

  • Lower pressure than petrol EFI
  • Requires diesel-compatible hose
  • Different filter requirements

Common Mistakes to Avoid

  • ❌ Undersized fuel lines - Causes fuel starvation at high RPM
  • ❌ Too many bends - Restricts flow and creates pressure drop
  • ❌ Lines too close to exhaust - Fire hazard and vapor lock
  • ❌ No fuel filter - Damages pump and injectors
  • ❌ Wrong fuel pressure - Poor performance or damage
  • ❌ Loose fittings - Leaks and fire hazard
  • ❌ No hose support - Vibration causes fatigue and failure
  • ❌ Mixing incompatible materials - Chemical degradation

Troubleshooting

Fuel starvation at high RPM:

  • Check line size is adequate for power output
  • Inspect for kinked or restricted hoses
  • Verify fuel pump flow rate is sufficient
  • Check fuel filter isn't clogged

Fuel leak at fitting:

  • Check fitting is properly tightened
  • Verify hose is fully seated on fitting
  • Inspect for damaged hose or fitting
  • Check O-rings (ORB fittings)

Low fuel pressure:

  • Check regulator setting
  • Verify pump is working correctly
  • Look for leaks in system
  • Check fuel filter isn't clogged

Vapor lock:

  • Route lines away from heat sources
  • Insulate or shield fuel lines
  • Consider electric fuel pump closer to tank
  • Check fuel pressure is adequate

Maintenance Schedule

  • Before each use (race cars): Visual inspection for leaks
  • Every 6 months: Check all connections, inspect hoses
  • Annually: Replace fuel filter, pressure test system
  • Every 2-3 years: Replace braided hoses (or as needed)
  • After any modification: Full pressure test and leak check

Need Help?

Technical Support:

📞 0417 391 414
📧 sales@racereadygear.com.au

Shop Fuel System Parts:

⚠️ Safety Warning: Fuel system work is dangerous. If you're not experienced with this type of work, hire a professional. Fuel leaks can cause fires and serious injury.

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