Yamaha Rhino 660 Fuel Pump Diagram Explained: Location, Function, Testing & Replacement Guide

The Yamaha Rhino 660 fuel pump diagram is essential for locating, testing, and replacing this critical fuel system component when issues arise. Understanding the pump's placement within the fuel tank assembly, its electrical connections, the fuel flow path, and associated parts like the fuel filter and pressure regulator is crucial for diagnosing problems like hard starting, engine hesitation, or stalling. Accessing the pump requires removing the driver-side seat, rear fender plastics, and unbolting the tank assembly. This guide provides a detailed breakdown of the Yamaha Rhino 660 fuel pump system using clear descriptions of its diagrammatic layout and function.

The Core Function of the Fuel Pump: Delivering Lifeblood. The sole purpose of the Yamaha Rhino 660 fuel pump is a vital one: to draw gasoline from the fuel tank and pressurize it, delivering a consistent stream of fuel to the Rhino’s fuel injection system. Fuel injection systems require specific pressure levels to operate correctly. The pump creates this pressure, ensuring atomized fuel spray necessary for efficient combustion. Without a properly functioning pump delivering the correct pressure and volume, engine performance suffers dramatically or ceases entirely.

Locating the Fuel Pump Assembly Inside the Tank. Unlike some vehicles with external fuel pumps, the Yamaha Rhino 660 utilizes a submerged pump assembly. This assembly is entirely housed within the fuel tank itself. Accessing it requires gaining entry to the top of the fuel tank. The entire fuel pump module – consisting of the electric pump motor, inlet strainer (sock filter), fuel level sending unit, fuel pressure regulator (integrated into the assembly on most Rhino 660s), and necessary tubing and wiring – is typically located towards the center or slightly off-center on the top of the fuel tank once the assembly is removed. Being submerged serves two key purposes: cooling the pump motor with surrounding fuel and providing consistent fuel feed even when tank levels are low.

Accessing the Fuel Pump: Gaining Entry to the Tank. Reaching the Yamaha Rhino 660 fuel pump module is a systematic process. Begin by parking the Rhino on a level surface, setting the parking brake, and disconnecting the negative battery terminal. Removal of the driver-side seat is necessary, typically involving several bolts accessible once the seat cushion is lifted. Next, remove the plastic rear fender assemblies surrounding the driver's seat area; these are usually held by a combination of push-pin retainers and screws/bolts. Underneath these plastics, the large metal plate forming the top of the fuel tank becomes visible. This top plate is sealed to the tank body and secured by numerous screws around its perimeter. Carefully remove all these screws, noting their locations as some lengths might differ. Before lifting the plate assembly containing the pump module, disconnect the electrical connector supplying power to the pump and fuel sender. Be prepared for residual fuel or fumes – have absorbent rags ready and ensure the work area is well-ventilated and away from ignition sources. Lift the pump module assembly straight up and out of the tank. The pump, filter, and pressure regulator are integral parts of this module.

Breaking Down the Fuel Pump Assembly Components. With the pump assembly removed from the tank, you can clearly identify its main parts, aligning with the diagram concept:

1. Fuel Pump Motor: The electric component that physically draws fuel in and pushes it out under pressure. It resembles a small cylindrical motor.
2. Inlet Strainer ("Sock Filter"): A mesh or fabric filter attached directly to the pump's inlet. Its job is to trap large debris particles suspended in the fuel before they can enter and damage the pump mechanism. This is the first line of defense for the pump.
3. Pump Housing/Canister: The plastic or metal casing enclosing the pump motor and providing mounting points.
4. Fuel Pressure Regulator: Often integrated into the top plate or housing of the Rhino 660 assembly. This diaphragm-operated valve regulates the pressure within the fuel rail feeding the injectors. It maintains a constant pressure by returning excess fuel back to the tank via the return line when needed.
5. Fuel Outlet Line: The rigid tube or port on the assembly carrying pressurized fuel from the pump towards the engine. This connects to the main fuel supply line exiting the tank assembly.
6. Fuel Return Line: An inlet or connection point where excess fuel returned from the pressure regulator re-enters the pump assembly housing to flow back into the tank.
7. Electrical Connector: A multi-terminal plug carrying the power supply and ground wires for the pump motor, and separate wires for the fuel level sender.
8. Fuel Level Sending Unit: A potentiometer attached to a float arm. As the fuel level rises and falls, the arm moves, changing the resistance value sent to the gauge on the instrument panel.
9. Tank Seal: A large rubber or composite o-ring gasket that seals the top plate assembly tightly to the fuel tank body. This is absolutely critical and must be replaced anytime the assembly is removed to prevent leaks.

Visualizing the Fuel Flow Path (The Diagram in Action). Understanding the sequence is key to diagnosing flow issues:

1. Sump Pickup: Fuel enters the assembly through the inlet strainer located at the bottom of the submerged pump module. This strainer filters out larger contaminants.
2. Pressurization: The fuel pump motor draws in the filtered fuel, pressurizes it significantly (typically within the range of 40-45 PSI for many Rhino 660s), and forces it out.
3. Pressurized Feed: Pressurized fuel exits the pump through the fuel outlet line located on the pump housing or top plate.
4. Supply Line to Engine: The outlet nipple connects to the fuel supply line, a reinforced rubber hose leading through the chassis frame rails up to the fuel rail on the engine's intake manifold/throttle body assembly.
5. Injection: Pressurized fuel reaches the fuel injector(s). The engine control unit (ECU) pulses the injector open to spray atomized fuel into the intake stream.
6. Pressure Regulation: Not all fuel delivered by the pump is needed by the injectors at all times. The fuel pressure regulator senses rail pressure. If pressure exceeds the specified threshold (around 40-45 PSI), the regulator diaphragm opens a passage allowing excess fuel to flow out of the regulator.
7. Return to Tank: This excess fuel flows back through a dedicated fuel return line attached to the regulator assembly port. The return line leads back into the pump module housing or directly into the top of the tank, effectively recycling the excess fuel and maintaining constant pressure in the supply line.

Electrical Connection Points: Powering the Pump. The fuel pump relies on a dedicated electrical circuit:

1. Power Source: Battery voltage flows through a fuse (located in the main fuse block, often labeled for the fuel system) to the fuel pump relay.
2. Relay Control: The ECU activates the fuel pump relay when the ignition is turned on (providing a brief prime pulse) and while the engine is cranking or running. When activated, the relay closes its contacts.
3. Power to Pump: Closing the relay contacts completes the circuit, sending battery voltage from the relay output terminal down a dedicated power wire to the fuel pump electrical connector terminal identified for power (often labeled with a letter like 'F' or color-coded, but diagram specifics are essential).
4. Ground Path: The circuit is completed via the ground wire connected to the pump connector (typically grounded through a chassis point near the tank or directly on the frame). This ground path must be clean and secure.

Common Symptoms of a Failing Yamaha Rhino 660 Fuel Pump. When the pump or components within its assembly wear out or fail, several telltale signs emerge:

1. Engine Cranks But Won't Start: The most classic sign. Lack of fuel pressure prevents combustion. This can also be caused by a failed pump relay or fuse, but the pump itself is a prime suspect.
2. Hesitation, Sputtering, or Lack of Power Under Load: Weak pump output, failing pressure regulator, or a severely clogged inlet strainer prevents the engine from getting enough fuel during acceleration or when pulling hard.
3. Engine Stalling During Operation: A pump that's cutting out intermittently due to internal wear, an electrical fault, or overheating (potentially related to low fuel levels) can cause the engine to suddenly die.
4. Whining or Humming Noise From Tank Area: Excessive noise from the pump motor can indicate wear, impending failure, or the pump running dry due to a clogged strainer.
5. No Noise From Pump at Key-On: In a functioning system, you should hear the pump run for 1-2 seconds when the ignition key is turned to 'ON' (engine not cranking). Complete silence suggests no power to the pump (check relay, fuse, wiring) or a completely dead pump motor.
6. Poor Fuel Economy: While less direct, a failing pump struggling to maintain pressure or a leaky pressure regulator can sometimes cause the system to run richer than necessary.

Testing the Fuel Pump and Circuit - Practical Diagnostics. Before condemning the pump, perform these checks:

1. Initial Checks: Verify the fuse is intact. Listen near the tank for the pump prime sound (1-2 seconds) when turning the key to ON. No sound? Proceed.
2. Check for Power & Ground at Pump Connector:
   • Disconnect the pump's electrical connector.
   • Turn the ignition key to ON (do not crank).
   • Using a digital multimeter (DMM), measure voltage between the connector's power pin and a known good ground. You should see battery voltage for ~2 seconds. If yes, power is reaching the connector. If not, the issue is upstream (relay, fuse, wiring, ECU command).
   • If power is present, test the ground pin continuity: Set DMM to resistance/ohms mode. Connect one lead to the ground pin on the wiring harness side of the disconnected connector. Connect the other lead to a good chassis ground point. Expect very low resistance (less than 1 ohm). High resistance indicates a poor ground path.
3. Testing the Pump Motor Itself: If power and ground are confirmed good at the connector during key-on prime but the pump doesn't run, or if suspected during operation:
   • Bench Test (Preferred): Safely remove the pump assembly from the tank (see Access section above). Apply direct battery voltage (use fused jumper wires!) to the pump motor's terminals (+ to positive terminal, - to negative terminal). A healthy pump should run smoothly and pump fluid if submerged in a container of fuel. EXTREME CAUTION: This involves sparks and fuel vapors. Perform outdoors away from ANY ignition sources. Never run the pump motor dry outside of fuel for more than a split second.
   • In-Tank Power Test (Simpler but Less Isolating): Reconnect the connector. Tap into the power wire feeding the pump (back-probe carefully or use a breakout harness). Monitor voltage during a crank attempt. Voltage should hold steady near battery voltage. If voltage sags dramatically or is absent, power delivery is weak. If voltage is good but pump is noisy/weak, the pump motor itself is suspect.
4. Checking the Inlet Strainer: Examine visually for heavy clogging with debris, varnish, or rust. Replace if clogged.
5. Suspecting Pressure Regulator: Requires a specialized fuel pressure gauge kit to test rail pressure. Connect the gauge to the test port on the fuel rail (if equipped) or tap into the supply line near the rail. Compare reading at prime (key-on), idle, and when revving under load against factory specifications (typically 40-45 PSI for the Rhino 660). Pressure lower than spec or unable to build pressure points to pump, regulator, or leaks. Pressure dropping significantly when engine is turned off or surging can indicate a faulty regulator diaphragm leaking internally or stuck closed.

Step-by-Step Yamaha Rhino 660 Fuel Pump Replacement. If diagnostics confirm a faulty pump assembly, follow this process:

1. Preparation: Park on level ground, parking brake on. Disconnect negative battery cable. Ensure ample ventilation and have fire extinguisher readily accessible. Purchase a new, high-quality fuel pump assembly specific to the Yamaha Rhino 660. This usually includes the pump motor, strainer, level sender, pressure regulator, gaskets, and sometimes the module top plate. Obtain a replacement tank seal ring – DO NOT reuse the old one.
2. Depressurize the System (Recommended): Locate the fuel pump fuse or relay in the main fuse box. Start the engine and let it run until it stalls from fuel starvation. Crank briefly again to ensure pressure is depleted. Turn ignition off.
3. Drain Fuel Tank: Siphon or use a drain plug (if equipped) to remove as much fuel as possible from the tank. This minimizes spillage and weight during removal. Place a large drain pan under the work area.
4. Gain Access: Remove the driver's seat. Remove rear fender plastics surrounding the seat area to expose the fuel tank top plate.
5. Disconnect Pump: Disconnect the electrical connector plugging into the pump module on the tank top plate.
6. Disconnect Fuel Lines: Using fuel line disconnect tools appropriate for the size, carefully disconnect the fuel supply line from the pump assembly nipple and the fuel return line (if present). Be prepared for residual fuel leaks; plug lines with golf tees or small bolts wrapped in Teflon tape if necessary to minimize spillage. Note the locations of each line before disconnecting.
7. Remove Assembly Bolts: Unscrew all bolts securing the tank top plate/pump assembly to the tank body. Keep track of bolt locations and lengths. A small hooked tool may help lift the plate if stuck.
8. Lift Out Assembly: Carefully lift the entire pump module assembly straight up and out of the tank. Avoid damaging the fuel level sender float arm. Place it on a clean surface.
9. New Tank Seal: Thoroughly clean the groove on the tank and the surface of the new top plate assembly where the large round seal ring seats. Apply a very thin smear of fresh engine oil or silicone grease (check seal instructions) to the new tank seal ring. Place it precisely into the groove on the fuel tank body.
10. Transfer Components (If Required): Unless the replacement is an exact top plate assembly replacement, you often need to transfer the fuel level sender unit and/or pressure regulator to the new pump body/housing according to the new kit instructions. Compare the old and new parts carefully. Swap the electrical connector harness if needed. Attach the new inlet strainer.
11. Installation: Lower the new/rebuilt pump module assembly straight down into the tank, ensuring the float arm isn't bent. Ensure it seats correctly on the seal ring. Hand-start all assembly bolts evenly around the perimeter in a crisscross pattern to avoid warping. Tighten progressively in a crisscross pattern to the specified torque (if available, otherwise firm but not excessive). Reconnect the fuel lines (supply and return) securely. Ensure hose clamps (if used) are positioned correctly and tightened. Reconnect the electrical connector firmly.
12. Refill Tank: Add a few gallons of fresh fuel to the tank. Inspect the seal area carefully for leaks.
13. Reassembly: Reinstall rear fender plastics. Reinstall the driver's seat.
14. Final Checks & Start: Reconnect the negative battery cable. Turn the ignition key to ON and listen for the pump prime cycle (2 seconds). Cycle the key ON/OFF a few times to purge any large air pockets (pump may prime each time). Attempt to start the engine. Monitor for leaks around the tank seal area again. Verify normal engine operation and fuel gauge function.

Preventative Maintenance for Longevity. While fuel pumps eventually wear out, you can maximize their lifespan:

• Use Clean, Quality Fuel: Contaminants and water accelerate pump wear and clog filters. Avoid stale gas or questionable sources.
• Keep the Tank Adequately Full: Submerged pumps rely on fuel for cooling. Running extremely low regularly can cause overheating and premature failure.
• Replace the Fuel Filter Regularly: While the Rhino 660 often has an inline filter (check your model year/service manual), the inlet strainer on the pump is the primary screen. If the Rhino exhibits symptoms or during major service, consider inspecting/cleaning/replacing the strainer. Some aftermarket pump kits include a replacement. Consult service intervals.
• Address Leaks Promptly: Fuel leaks introduce air into the system and pose a fire hazard. Repair fuel lines, connectors, or injectors leaking promptly.

Essential Safety Reminders. Working with fuel systems demands utmost caution:

• NO IGNITION SOURCES: Never smoke or work near sparks, flames, or anything generating heat during removal, testing, or installation.
• VENTILATION IS KEY: Perform all fuel tank access work outdoors or in a very well-ventilated garage.
• GROUND YOURSELF: Static discharge can ignite fuel vapor. Touch bare metal on the frame before handling fuel system components.
• EYE & SKIN PROTECTION: Wear safety glasses and nitrile gloves. Gasoline is irritating and hazardous.
• FIRE EXTINGUISHER: Have a Class B (flammable liquids) fire extinguisher immediately at hand.
• PROPER CONTAINMENT: Use approved containers for fuel. Have absorbent pads ready to catch spills.
• DON’T RUN THE PUMP DRY: Testing the motor briefly outside the tank is acceptable only if submerged in a container of fuel first or for less than a second for functional check. Extended dry running destroys the pump.

Accurate visualization of the Yamaha Rhino 660 fuel pump diagram – its physical location submerged within the tank assembly, its path for drawing fuel in through the inlet strainer, pressurizing it, and delivering it to the engine via the fuel rail, along with the role of the pressure regulator maintaining constant pressure through the return line – combined with understanding the dedicated power supply circuit controlled by the ECU and relay, provides the necessary framework for confident diagnosis and repair. Recognizing the symptoms of pump failure, performing systematic voltage checks, verifying fuel pressure levels when necessary, and following safe removal and replacement procedures empowers Rhino 660 owners to effectively resolve common fueling issues. Consistent use of quality fuel and maintaining reasonable tank levels also contributes to long-term fuel pump reliability.