Fuel Line Replacement | Small Engine Repair Guide

Cracked or clogged fuel lines cause starting problems and fuel leaks. Replacing them is cheap and easy. This guide covers fuel line replacement for all types of small engine equipment.

Table of Contents

• When to Replace
• Fuel Line Types
• Tools and Materials
• Lawn Mower Fuel Lines
• Trimmer and Chainsaw Lines
• Fuel Filter Replacement

When to Replace

Signs of Bad Fuel Lines

Visible cracks - Ethanol in modern gas degrades rubber. Cracked lines leak and allow air in.

Hardened lines - Old lines become stiff and brittle. They crack when flexed.

Fuel smell - Leaking lines cause fuel odor. Fire hazard.

Won’t stay primed - Air leaks through bad lines prevent priming.

Engine dies - Failing lines starve engine of fuel.

[NEED REAL IMAGE: Cracked fuel line comparison]

Replacement Schedule

• Every 2-3 years for regular use
• Immediately if cracked or leaking
• After extended storage (check before use)

Fuel Line Types

Standard Rubber

Most common on mowers and larger equipment.

Sizes:

• 1/4” ID - Most push mowers
• 5/16” ID - Riding mowers
• 3/8” ID - Large equipment

Tygon/Clear Lines

Used on trimmers and chainsaws for visibility.

Sizes:

• 3/32” ID - Small 2-stroke
• 1/8” ID - Standard 2-stroke
• 3/16” ID - Larger 2-stroke

Braided Lines

Reinforced for high-pressure applications.

Used on fuel injection or high-pressure pumps.

Tools and Materials

Tools Needed

• Needle-nose pliers
• Flathead screwdriver
• Wire cutters or sharp knife
• Container for fuel
• Shop towels

Materials

• Replacement fuel line (correct size)
• Fuel filter (if replacing)
• Hose clamps (if used)
• Fuel-safe sealant (rarely needed)

Fuel Line Sources

Brand	Part Number	Application
Briggs	395051	1/4” universal
Tygon	F-4040-A	Clear 1/8”
Oregon	07-152	Trimmer kit
Stens	115-014	5/16” mower

Lawn Mower Fuel Lines

Push Mower Replacement

Step 1: Drain fuel

Run engine until tank is nearly empty or siphon fuel out.

Step 2: Access lines

Remove engine shroud if needed to access fuel connections.

Step 3: Note routing

Take photos before removing old lines. Note which line goes where.

Step 4: Remove old lines

• Pinch and pull off connections
• Cut stubborn lines if needed
• Remove fuel filter if inline

Step 5: Measure and cut new line

• Cut slightly longer than old line
• Ensure clean square cuts

Step 6: Install new lines

• Push firmly onto fittings
• Reinstall clamps if used
• Ensure no kinks

Step 7: Test

• Fill tank partially
• Check for leaks
• Start and run engine

[NEED REAL IMAGE: Push mower fuel line routing]

Riding Mower Replacement

More complex due to fuel pump and multiple lines.

Lines to check:

1. Tank to fuel pump
2. Fuel pump to carburetor
3. Return line (if equipped)

Fuel pump lines:

Riding mowers have pulse-type fuel pumps.

• Input from tank
• Output to carb
• Pulse line from engine

All three lines can crack and cause problems.

Step 1: Locate all lines

Follow from tank through pump to carburetor.

Step 2: Drain and disconnect

• Close fuel valve or pinch lines
• Have container ready
• Remove one line at a time

Step 3: Replace systematically

Work from tank toward carburetor. Replace all if any are bad.

Step 4: Check clamps

Use spring clamps or worm gear clamps. No clamps = leaks eventually.

Trimmer and Chainsaw Lines

2-stroke equipment has fuel lines inside the tank.

Trimmer Fuel System

Components:

• Fuel pickup line (goes to bottom of tank)
• Fuel filter (weighted, stays at bottom)
• Supply line to carburetor
• Return line (some models)

Replacement:

1. Drain fuel tank
2. Remove fuel cap
3. Use hooked wire to pull lines from tank
4. Note filter attachment
5. Attach new filter to pickup line
6. Thread new lines through grommets
7. Connect to carburetor
8. Test for leaks

[NEED REAL IMAGE: Trimmer fuel line routing]

Chainsaw Fuel System

Similar to trimmer but may have:

• Larger diameter lines
• Vent line
• Separate oil pickup (for bar oiler)

Stihl chainsaws: Use specific sized Tygon lines.

• Fuel pickup: 3/32” ID
• Fuel supply: 1/8” ID

Echo chainsaws: Similar sizing. Use manufacturer specs.

Common 2-Stroke Line Kits

Pre-made kits include correct sized lines and filter.

Brand	Kit Contents	Price
Poulan	Lines + filter	$8-12
Stihl	OEM lines	$12-18
Echo	Lines + filter + grommet	$10-15
Universal	Bulk line + filters	$15-20

Fuel Filter Replacement

Replace fuel filter when replacing lines.

Inline Filters (Mowers)

Located between tank and carburetor.

Replacement:

1. Pinch lines on both sides
2. Pull filter from lines
3. Note flow direction (arrow on filter)
4. Push new filter into lines
5. Ensure secure fit

In-Tank Filters (2-Stroke)

Attached to end of pickup line inside tank.

Replacement:

1. Pull old filter and line from tank
2. Cut old filter from line
3. Push new filter onto new line
4. Drop weighted filter into tank
5. Ensure filter moves freely

[NEED REAL IMAGE: Fuel filter types comparison]

Filter Sizes

Application	Filter Type	Size
Push mower	Inline	1/4”
Riding mower	Inline	5/16”
Trimmer	In-tank	Small weighted
Chainsaw	In-tank	Felt or nylon

Troubleshooting

Fuel Still Won’t Flow

Check:

• Tank vent (cap vent blocked?)
• Fuel shutoff valve
• Filter clogged already (bad gas)
• Lines kinked

Engine Still Won’t Start

Fuel system good but still won’t start:

• Carburetor clogged
• Spark issue
• Compression problem

Fuel Leaks After Replacement

Causes:

• Lines not fully seated
• Wrong size line (too small)
• Cracked fitting
• Missing clamp

Ethanol and Fuel Lines

E10 Gas Effects

Standard E10 (10% ethanol) gas degrades rubber over time.

Symptoms:

• Lines become gummy inside
• Rubber swells then cracks
• Fuel picks up rubber debris

E15/E85 Damage

Higher ethanol content (E15, E85) destroys standard fuel lines quickly.

Never use E15 or higher in small engines.

Ethanol-Resistant Lines

For maximum life, use ethanol-resistant lines:

• Tygon F-4040-A
• Gates Barricade
• Manufacturer OEM lines

Related Guides

• How to Clean a Carburetor
• Small Engine Fuel Problems
• Lawn Mower Won’t Start
• String Trimmer Won’t Start
• Chainsaw Won’t Start

Summary

Fuel line replacement is one of the easiest and most impactful repairs. Cracked lines cause hard starting and leaks. Replace them every 2-3 years or immediately if damaged. Use the correct size and ethanol-resistant material. Always replace the fuel filter at the same time. Most jobs take under 30 minutes and cost less than $20 in parts.