If your Honda Rancher 420 won’t start or suddenly dies, a faulty fuel pump relay could be the culprit. Understanding Honda Rancher 420 Fuel Pump Relay Problems is the first step to getting your ATV running again.
This common issue can leave you stranded, but the good news is that it’s often a fix you can handle yourself. We’ll walk you through how to diagnose a bad relay, where to find it, and how to replace it with confidence.
Honda Rancher 420 Fuel Pump Relay Problems
The fuel pump relay is a simple electromechanical switch. It controls power to your Rancher’s fuel pump. When you turn the key, the ECU sends a signal to the relay, which closes its internal circuit and sends 12-volt power to the pump.
A failing relay interrupts this process. Without consistent power, the fuel pump can’t send gas to the engine. This leads to starting failures or sudden stalling, even if the pump itself is in perfect condition.
Common Symptoms of a Failing Relay
How do you know if the relay is the problem? Look for these signs:
- No-start condition: You turn the key and hear only the starter motor, but the engine doesn’t crank. Listen carefully for a faint humming from the fuel tank area when you first turn the key; if it’s silent, the pump isn’t getting power.
- Intermittent starting: The ATV starts fine sometimes but not others, often after sitting for a while or when the weather is hot or cold.
- Engine stalls while riding: The Rancher suddenly loses power and dies as if it ran out of fuel, but the tank is full.
- Clicking sound from the relay box: You might hear a rapid clicking noise coming from under the seat when you try to start it, indicating the relay is trying but failing to engage properly.
- No fuel pump prime sound: When you first turn the key to “ON” (before starting), you should hear a brief whirr from the fuel pump for about two seconds. Its absence is a major clue.
Where is the Fuel Pump Relay Located?
On the Honda Rancher 420, the relay is part of a group of relays and fuses housed in a black box. The location is under the seat, on the left-hand side of the ATV near the battery compartment.
To access it, you’ll need to remove the seat. This is usually done by pulling up on the latch at the rear of the seat and then lifting it off. Once the seat is removed, you’ll see the rectangular relay box with a removable lid.
Identifying the Correct Relay
The box contains several similar-looking relays. Using the wrong one will waste your time. Here’s how to find the right one:
- Consult your owner’s manual. The diagram on the inside of the relay box lid will show which relay is for the fuel pump.
- Typically, it’s one of the larger, cube-shaped relays (often a 5-pin) rather than the smaller fuses or mini-relays.
- If the diagram is missing, you can often identify it by listening or feeling for a click. With the key turned to “ON,” have a helper listen while you gently tap or swap relays; the fuel pump relay should click once when the key is turned.
How to Test the Fuel Pump Relay
Before you buy a new part, it’s smart to test the old relay. You’ll need a basic multimeter.
Visual Inspection
First, pull the suspect relay straight out of its socket. Look for obvious signs of damage:
- Burnt or melted plastic on the relay casing.
- Corroded or bent pins on the bottom.
- A burnt smell coming from the relay.
The Swap Test (Easiest Method)
This is a quick and reliable diagnostic. Find another relay in the box that is identical in shape and pin configuration. Common candidates are the starter relay or the cooling fan relay.
- Carefully pull out the identical, known-good relay.
- Swap it with the suspected fuel pump relay.
- Turn the key to “ON.” Listen for the fuel pump prime sound.
- If the pump now primes and the ATV starts, you’ve confirmed the original fuel pump relay is bad.
Multimeter Continuity Test
For a more precise test, use a multimeter set to measure resistance (Ohms).
- Identify the relay’s coil pins (usually two pins that are aligned). You may need to look up the relay’s pin diagram online using the number printed on its side.
- Place the multimeter probes on these two coil pins. You should get a reading (typically between 50-150 ohms). An “OL” (open line) reading means the coil is broken and the relay is dead.
- Next, test the switch pins. With no power to the relay, the switch circuit should be open (OL reading). You can sometimes test it by applying 12V from the battery to the coil pins (be careful of polarity) and then checking for continuity across the switch pins; it should close and show near-zero resistance.
Step-by-Step Relay Replacement Guide
Once you’ve confirmed the relay is faulty, replacing it is straightforward.
Tools and Parts Needed
- New Honda fuel pump relay (Part number is often 38501-HN1-681 or similar, but always verify with your VIN). A standard automotive relay with the same pin configuration may also work.
- Your hands (usually no tools are needed to remove the relay).
- Maybe a small flat-head screwdriver to gently pry the relay box lid off.
Replacement Steps
- Ensure the ATV is off and the key is removed.
- Remove the seat to access the relay box.
- Open the lid of the relay box.
- Locate the faulty fuel pump relay.
- Grasp it firmly and pull it straight up and out of its socket. Don’t wiggle it excessively.
- Align the new relay’s pins with the socket. Note that one pin might be offset or a different shape to prevent incorrect installation.
- Press the new relay down firmly until it seats completely.
- Close the relay box lid and reinstall the seat.
- Turn the key to “ON” and listen for the fuel pump’s 2-second priming sound.
- Start the engine. It should fire up normally.
Preventing Future Relay Problems
Relays can fail from age, heat, and moisture. While you can’t stop them from ever wearing out, you can extend their life.
- Keep it Dry: After washing your Rancher or riding in wet conditions, try to dry the area around the relay box. Ensure the lid is sealed properly.
- Check Connections: Periodically, when doing other maintenance, check that the relay is fully seated and that no corrosion is on the pins in the socket.
- Carry a Spare: Given their small size and critical role, it’s a good idea to keep a known-good spare relay in your tool kit. This can be a lifesaver on the trail.
When the Problem Isn’t the Relay
If you replace the relay and the problem persists, the issue lies elsewhere in the fuel or electrical system. Here are other components to check:
Main Fuse
A blown main fuse will cut power to the entire system, including the relay. Check the large 30A or 40A main fuse, usually located near the starter solenoid or in the relay box.
Fuel Pump Itself
The pump motor can burn out. You can often hear it trying to run if you listen closely at the fuel tank. Directly testing for 12V at the pump connector (when the key is on) will tell you if power is getting past the relay.
Ignition Switch or Side Stand Switch
A faulty ignition switch may not send the signal to activate the relay. The Rancher’s safety system includes a side stand switch; if it fails, it can prevent the fuel pump from getting the signal to run.
Wiring and Grounds
Corroded, frayed, or loose wires in the circuit between the ignition, relay, and pump can cause identical symptoms. Pay special attention to ground connections, which are a frequent source of electrical gremlins.
FAQ Section
What does a fuel pump relay do on a Honda Rancher 420?
It acts as a switch, using a small electrical signal from the ignition to send full battery power to the fuel pump, which then pressurizes the fuel system for starting and running.
Can I bypass the fuel pump relay to test it?
Yes, but do so cautiously and only as a temporary test. You can create a jumper wire to connect the battery power pin to the fuel pump output pin in the relay socket. If the pump runs and the engine starts with the jumper in place, the relay is bad. Never ride with a bypass in place.
How much does a new Honda Rancher 420 fuel pump relay cost?
A genuine Honda relay typically costs between $25 and $45. Aftermarket or generic equivalents can be found for less, sometimes under $15.
Why does my Rancher’s relay keep failing?
Repeated failures could point to an underlying issue. A weak fuel pump drawing too much current can overload and burn out the relay. Voltage spikes from a failing stator or regulator/rectifier can also damage electronic components like relays. It’s worth investigating these if relays fail often.
Is it safe to use a different relay in my Honda ATV?
If the pin configuration (4-pin vs. 5-pin) and the amperage rating are identical, a standard automotive relay will usually work. However, for reliability and fit, a Honda OEM part is recommended.
Dealing with Honda Rancher 420 fuel pump relay problems can be frustrating, but the fix is usually simple and inexpensive. By following the diagnostic steps, you can quickly determine if the relay is at fault. Remember to always start with the simplest checks first, like the swap test, before moving on to more complex components. With a new relay installed, you’ll likely be back on the trail in no time, enjoying your reliable Rancher once again.