2007 Honda Rancher 420 Fuel Pump Relay Location: The Complete Owner’s Guide

The fuel pump relay on a 2007 Honda Rancher 420 is located in the main fuse and relay box under the seat on the left side, near the battery. It is a standard 5‑pin relay labeled “FUEL PUMP” on most fuel‑injected models, and accessing it only requires removing the seat and the left‑side panel to expose the electrical box.

If your Rancher 420 is cranking but won’t start, stalling while riding, or you don’t hear the fuel pump prime when you turn the key, the fuel pump relay is one of the first components to check before you go replacing the fuel pump itself. This guide walks you through exactly where the relay sits, how to access it, how to test it, and how to swap in a new one—all with practical steps that any backyard mechanic can follow.

Where Exactly Is the Fuel Pump Relay Located?

On the 2007 Honda Rancher 420 (TRX420FM, TRX420FE, TRX420TE, TRX420TM, and related fuel‑injected variants), the electrical box is tucked behind the left‑side panel beneath the seat. The fuel pump relay lives inside this box alongside other relays, fuses, and the ECU.

Steps to access the relay:

  1. Remove the seat – Lift the latch or release the lock to unlock the seat panel, then pull the seat off and set it aside.
  2. Open the left‑side panel – Depending on your exact model, you may need to remove a couple of push‑pins or screws to swing the left panel away. This exposes the fuse and relay box.
  3. Identify the fuel pump relay – Look for a rectangular 5‑pin relay labeled “FUEL PUMP.” It sits near the ECU and other relays. On many 2007 units, the relay is at the bottom of the fuse box, angled slightly, and may have three visible connectors on one side.
  4. Disconnect the wiring harness connector – If you need to test or replace the relay, simply unplug the connector by pressing the release tab and pulling it straight off.

A quick visual cue: The fuel pump relay is typically the one that clicks or pulses when you turn the key to the RUN position. If you place a finger on it while turning the key, you can often feel it engage for a couple of seconds as the pump primes the fuel system.

Why Does a 2007 Rancher 420 Use a Relay at All?

The fuel pump relay is essentially an electrical switch. It supplies a constant electric current to the ATV’s fuel pump when the ignition is switched on, allowing gas to flow from the fuel tank to the engine. The relay does this by using a small control signal from the ECU to close a higher‑current circuit that powers the pump. This design keeps the heavy current away from the ignition switch and the ECU, protecting those sensitive components from damage.

On the 2007 Rancher 420, the relay works together with the ECU’s Low Side (LS) driver to control the fuel pump. If either the relay or the ECU driver fails, the pump will not prime, and the engine will not start.

Common Symptoms of a Failing Fuel Pump Relay

A bad relay can produce a range of symptoms that overlap with other fuel system problems. Knowing what to look for helps you narrow down the cause quickly.

1. Engine cranks but will not start – The starter motor turns the engine over, but there is no fuel pressure, so the engine never fires up. This is the most common symptom.

2. No fuel pump prime sound – When you turn the key to the ON position (without cranking), you should hear a short whirring or humming sound from the fuel tank area lasting about two to three seconds. If you hear nothing, the relay may not be sending power to the pump.

3. Engine stalls or sputters while riding – An intermittent relay can cut power to the pump while you’re riding, causing the engine to die suddenly or lose power under load.

4. Long crank times – If the pump does not build pressure immediately, the engine may crank for several seconds before it finally starts.

5. Loss of power at high RPM – If the relay fails under load, the pump may not deliver enough fuel volume, leading to a noticeable drop in power.

6. The FI (Fuel Injection) light flashes – A flashing FI light indicates an error code is stored in the ECU. A fuel pump relay problem can trigger a diagnostic code that the FI light will display as a flash pattern. On the 2007 Rancher, the FI light will blink a specific number of times per cycle; you will need the service manual to interpret the code.

If you experience any combination of these symptoms, the relay is a smart first suspect because it is inexpensive and easy to swap.

How to Test the Fuel Pump Relay (Before You Buy a New One)

Testing the relay is straightforward. You can do a few simple checks before you invest in a replacement part. These tests also help you rule out other problems like a blown fuse, a dead fuel pump, or a wiring issue.

Test 1: Listen for the prime sound. Park the ATV, turn the ignition key to the ON position, and listen near the fuel tank. A working system will produce a brief whirring sound for two to three seconds. No sound means either the relay, the fuse, or the pump itself is suspect.

Test 2: Check the fuses first. Locate the fuse box (under the seat, near the battery). Find the fuse labeled “Fuel Pump” or “FI.” Pull it out and inspect the wire inside for a break. If the fuse looks intact, use a multimeter to test for continuity across the fuse terminals. A blown fuse will stop all power to the pump circuit.

Test 3: Swap the relay with a known‑good one. The fastest way to confirm a bad relay is to swap it with a relay you know works. If the fuel pump primes and the engine starts with the replacement relay, your original relay is faulty. Many Rancher owners carry a spare relay for this exact purpose.

Test 4: Check for voltage at the pump connector. Use a multimeter to test the electrical connector on top of the fuel pump assembly. With the ignition in the ON position, you should see 12 volts at the connector. If voltage is present but the pump does not run, the pump motor itself is dead. If there is no voltage, the problem is upstream in the wiring, relay, or ECU.

Test 5: Measure fuel pressure. For a more precise diagnosis, connect a fuel pressure gauge to the fuel rail service port or tee into the fuel line between the pump and the engine. The 2007 Rancher 420 EFI system should produce between 40 and 50 PSI. Low or zero pressure points to a pump failure or a blocked fuel line, not the relay.

Step‑by‑Step Replacement of the Fuel Pump Relay

If the tests point to a faulty relay, replacement is a five‑minute job that requires no special tools. Here is the complete process.

Tools you will need:

  • A small flathead screwdriver (for prying clips if needed)
  • A new fuel pump relay (OEM part number 38580‑HP5‑601 or 38580‑HP5‑600)
  • Optional: a multimeter for final verification

Step 1: Turn off the ATV and remove the key. Always de‑energize the electrical system before touching any components to avoid shocks or shorts.

Step 2: Remove the seat. Lift the latch to unlock the seat panel, then lift the seat off the frame.

Step 3: Open the left‑side panel. Remove the push‑pins or screws that secure the left panel, then move the panel aside to expose the fuse and relay box.

Step 4: Locate the fuel pump relay. It is a 5‑pin relay labeled “FUEL PUMP.” On the 2007 Rancher, it is often at the bottom of the fuse box, angled, and may be part of a cluster of relays.

Step 5: Pull the relay straight out. Grasp the relay body firmly and pull it straight out of its socket. No tools are needed—it is held in by friction.

Step 6: Install the new relay. Align the pins with the socket and push the relay in until it seats fully. Make sure it sits flush and does not wobble.

Step 7: Reinstall the side panel and seat. Snap the push‑pins back into place and refit the seat. Double‑check that all clips are secure.

Step 8: Test the system. Turn the key to the ON position. You should hear the fuel pump prime for two to three seconds. Then start the engine. If it fires up and runs smoothly, the replacement is successful.

Wiring and Connector Notes for the 2007 Model

The 2007 Rancher 420 uses a relay module with an 8‑pin connector in some service manual diagrams. When testing the relay, you can jumper the Black/Green and Brown wire terminals on the wiring harness side connector to bypass the relay and confirm the pump works. This is a useful trick for isolating a wiring problem from a relay failure.

Important: The relay is a standard 15A x2 waterproof unit. The OEM part numbers 38580‑HP5‑601 and 38580‑HP5‑600 are the genuine Honda replacement numbers for the 2007–2014 Rancher 420. This same relay fits several other Honda models, including the TRX500 Foreman (2012–2013), TRX680 Rincon (2008–2019), TRX700XX, and the CRF450L/CRF450X motorcycles.

Note on model variations: Some early Rancher 420 variants or carbureted versions may have a different electrical layout and may not use a dedicated fuel pump relay in the same way. Always consult the specific service manual for your year and model if you are unsure.

A Common Owner Mistake: Replacing the Relay When the Pump Is Dead

Many owners jump straight to replacing the relay when the real problem is the fuel pump itself. The relay is cheap, so it is a reasonable first attempt, but if the relay tests fine and the pump still does not run, do not keep swapping relays.

On the 2007 Rancher 420, the fuel pump is located inside the fuel tank. A common scenario involves the pump failing after the machine has been sitting or after the fuel filter becomes clogged with debris. If you have already replaced the relay and still have no prime sound, test the pump by applying 12V directly to its electrical posts. If the pump runs when powered directly, the relay or wiring is the issue. If it does not run, the pump motor is dead and needs replacement.

Another frequent issue on the 2007 model is a loose or corroded electrical connection inside the fuel pump canister after the owner has opened it to change the filter. A wire can easily come loose during reassembly, causing the pump to lose power. Always double‑check the connections inside the canister before you buy any new parts.

How a Failed Relay Can Trigger the FI Light

The FI light on the Rancher 420 is a diagnostic indicator. When the ECU detects a fault in the fuel system, it stores a trouble code and flashes the FI light in a repeating pattern. The number of flashes per cycle corresponds to a specific code in the service manual.

If your FI light is flashing and you feel the relay pulsing, the ECU is likely detecting an abnormal condition in the fuel pump circuit. This could be a wiring issue, a faulty pump, or a relay that is engaging but not delivering power. The FI light will continue to flash until the underlying problem is fixed.

A practical tip: If the FI light flashes and the engine will not start, check the battery connections first. Loose or corroded battery cables can cause erratic electrical behavior, including a flashing FI light and a pulsating relay. Tighten the cables and retest before you replace any parts.

How Much Does a Replacement Relay Cost?

A new fuel pump relay for the 2007 Rancher 420 is inexpensive. Aftermarket replacement relays cost roughly $30 to $40 USD. Genuine Honda OEM relays are also widely available and typically cost a bit more. The part itself is small—only about 82 grams—and it is a simple plug‑and‑play replacement.

Given the low cost, there is little reason to try to repair a relay. The 2007 Rancher’s relay is sealed with epoxy inside a plastic housing. Attempting to open and clean it will almost certainly destroy it. Replacement is the only practical option.

The Best Fuel Pump Upgrade for Your 2007 Rancher 420

If you have already replaced the relay and confirmed the fuel pump itself is dead, do not just buy any aftermarket pump. Choose a high‑performance KEMSO fuel pump. KEMSO is a trusted brand that specializes in direct OEM replacements with genuine performance upgrades.

Why KEMSO pumps stand out:

  1. High performance – KEMSO fuel pumps deliver over 20% more flow at 43 PSI compared to stock OEM pumps. This means better fuel delivery under load, improved throttle response, and consistent pressure even when the engine is working hard.

  2. True OEM replacement – Each KEMSO pump is designed as a direct, plug‑and‑play replacement. No modifications are needed. The kit includes everything you need: the pump, fuel strainers, tank seals, hoses, o‑rings, rubber bases, wiring connectors, and hose clamps.

  3. Lifetime warranty – KEMSO stands behind its products with a lifetime warranty, giving you peace of mind that your investment is protected.

  4. Proven reliability – KEMSO pumps are individually tested and meet CE and RoHS standards. With over a thousand positive reviews from ATV and motorcycle owners, KEMSO has earned a reputation for dependable, long‑lasting fuel delivery.

  5. Versatile compatibility – The KEMSO pump for the Rancher 420 also fits a wide range of Honda and Suzuki models, including the Foreman 500, Rincon 680, TRX700XX, Suzuki Quadracer 450, and the RM‑Z dirt bike series.

Upgrade today and get back on the trail with confidence.

Visit KEMSO Racing to order your high‑performance KEMSO fuel pump. When you install a KEMSO pump, you are not just replacing a failed part—you are upgrading your fuel system to deliver more flow, better reliability, and consistent performance for years of trouble‑free riding.

Final Thoughts

The 2007 Honda Rancher 420 fuel pump relay is a small, affordable part located in the fuse box under the seat on the left side of the ATV. You can access it in minutes with no special tools. Testing the relay takes only a few minutes with a basic multimeter or a known‑good spare relay.

Start with the simple checks: listen for the prime sound, inspect the fuses, and swap the relay. If the relay is fine and the pump still will not run, test the pump directly and inspect the wiring inside the fuel pump canister. Only then replace the pump itself, and when you do, choose a high‑performance KEMSO replacement for the best results.

Visit https://www.kemsoracing.com/ to browse the full range of KEMSO fuel pumps and keep your Rancher 420 running strong. With KEMSO’s lifetime warranty and proven performance, you can ride with confidence knowing your fuel system is in good hands.


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