The Ultimate Guide to the Fuel Pump for Polaris Ace 150, 500, 570, and 900 Models (2017 2018 2019 2020 2021)

For owners of the Polaris Ace 150, Ace 500, Ace 570, and Ace 900 from model years 2017, 2018, 2019, 2020, and 2021, the fuel pump is a critical component for reliable performance. This in-tank electric pump is responsible for delivering a consistent, high-pressure stream of fuel from the gas tank to the engine's fuel injectors. A failing pump can lead to a wide range of problems, from hard starting and poor performance to a complete engine stall. This comprehensive guide will explain everything you need to know about the fuel pump for your specific Ace model, including its function, common failure symptoms, detailed testing procedures, and a complete walkthrough for replacement.

Understanding the role of the fuel pump is the first step in maintaining your Polaris Ace. Unlike older carbureted systems, modern fuel-injected engines like those in the Ace series require precise fuel pressure to operate correctly. The pump is typically housed inside the fuel tank, submerged in gasoline which helps to cool and lubricate it. When you turn the key to the "ON" position, you should hear a brief humming sound for a few seconds—this is the pump priming the system to the correct pressure (typically around 39-43 PSI for these models). It then runs continuously while the engine is operating, adjusting its output based on demands from the Engine Control Unit (ECU). Any disruption in this flow or pressure will immediately affect how your Ace runs.

Recognizing the Symptoms of a Failing Fuel Pump

Catching a fuel pump problem early can prevent you from being stranded on the trail. The symptoms often start intermittently and worsen over time. Here are the most common signs to watch for in your Polaris Ace 150, 500, 570, or 900.

1. Engine Cranks But Won't Start
This is one of the most definitive signs. If your engine turns over strongly but never fires, it often points to a lack of fuel delivery. Before condemning the pump, always check for other simple issues like a clogged fuel filter, a blown fuse (check the 15A fuel pump fuse in the main fuse block), or a faulty fuel pump relay. However, a silent fuel pump when the key is turned on is a strong indicator.

2. Loss of Power Under Load (Bogging Down)
Your Ace might start and idle fine but then sputter, hesitate, or lose all power when you accelerate or climb a hill. This happens because a weak pump cannot maintain the required fuel pressure when the engine demands more fuel. The engine may feel like it's "running out of gas" even with a full tank.

3. Intermittent Stalling or Surging
If the fuel pump is beginning to fail electrically or its internal components are wearing out, it may work sporadically. This can cause the engine to suddenly stall while riding, then perhaps restart after sitting for a few minutes. You might also experience unexpected surges in power as the pump temporarily regains function.

4. Loud Whining or Humming Noise from the Fuel Tank
While the pump does make a normal priming hum, an unusually loud, high-pitched whining or groaning noise that persists while driving is a classic sign of a pump working too hard, often due to a clogged internal filter or impending bearing failure.

5. Difficulty Starting When the Engine is Hot (Heat Soak)
A failing pump may work adequately when cold but struggle after the engine and fuel tank have become hot. This is due to increased wear and reduced efficiency of the pump's electric motor. If your Ace consistently starts poorly after a hot shutdown but is fine when cold, the pump is a likely suspect.

Diagnostic Steps Before Replacing the Fuel Pump

Replacing a fuel pump is a significant task, so proper diagnosis is crucial. Follow these steps to confirm the pump is the issue for your Polaris Ace.

Step 1: Perform the "Key-On" Listen Test.
Turn the ignition key to the ON position (do not start the engine). Listen carefully near the fuel tank. You should hear a distinct humming sound from the fuel pump for approximately 2-3 seconds as it pressurizes the system. If you hear nothing, proceed to check electrical supply.

Step 2: Check Electrical Supply.
Locate the main fuse box, usually under the hood or near the battery. Find the 15-amp fuel pump fuse and inspect it. Use a multimeter to check for continuity or simply replace it with a known-good fuse. Next, locate the fuel pump relay. It is often in the same fuse block. You can try swapping it with an identical relay (like the horn or fan relay) to see if the problem is resolved. If there is still no power, wiring or ECU issues may be at fault.

Step 3: Check Fuel Pressure (The Most Accurate Test).
This is the definitive test. You will need a fuel pressure test gauge with the correct adapter for the Schrader valve on your Ace's fuel rail. The valve looks like a tire valve stem and is usually on the fuel line near the throttle body.

  • Connect the gauge securely.
  • Turn the key to ON to prime the system. The gauge should jump to a specified pressure. For most Ace 500, 570, and 900 models, this is 39-43 PSI. The Ace 150 may have a slightly different specification; consult your service manual.
  • Start the engine. The pressure should hold steady at the specified range at idle.
  • Pinch or clamp the fuel return line (carefully). The pressure should spike significantly, indicating the pump is capable of generating high pressure. If the pressure is low, does not hold, or fails to rise when the return line is restricted, the fuel pump assembly is likely failing.

Step-by-Step Fuel Pump Replacement Guide for Polaris Ace Models

Once you've confirmed the fuel pump is faulty, replacement is the solution. The process is similar for the Ace 150, 500, 570, and 900, with minor variations in tank size and mounting. Always work in a well-ventilated area, away from sparks or open flames. Relieve fuel system pressure before starting.

Tools and Parts Needed:

  • New fuel pump assembly (OEM or high-quality aftermarket like Quantum, Delphi)
  • Socket set and wrenches
  • Fuel line disconnect tools (the correct size for your model)
  • Drain pan for gasoline
  • Shop towels and safety glasses
  • New fuel filter (often integrated with the pump assembly)
  • New locking ring if not included with the pump

Procedure:

1. Depressurize the System and Disconnect the Battery.
Start by locating the fuel pump fuse or relay. Start the engine and let it run until it stalls from lack of fuel. Crank it a few more seconds to ensure pressure is relieved. Disconnect the negative battery terminal for safety.

2. Drain and Remove the Fuel Tank.
Place the drain pan underneath. Disconnect the fuel feed and return lines using the disconnect tools—push the tool into the fitting to release the locking tabs, then pull the line off. Disconnect the electrical connector to the pump. Remove any tank straps, bolts, or brackets holding the tank in place. Carefully lift the tank out of the vehicle. It is easier to fully remove the tank than to try to service the pump with the tank in place.

3. Access and Remove the Old Fuel Pump Assembly.
With the tank on a stable surface, clean the area around the pump mounting flange on top of the tank. Remove the locking ring that secures the pump. This usually requires a special spanner wrench or a careful tap with a brass punch and hammer. Turn it counter-clockwise. Once the ring is off, carefully lift the entire pump and sending unit assembly out of the tank. Be mindful of the float arm for the fuel level sender so as not to bend it.

4. Transfer Components and Install the New Pump.
Compare the old and new pump assemblies. You may need to transfer the fuel level sender/float arm from the old assembly to the new one if it is not pre-installed. Also, ensure the new pump's filter sock is properly attached. Install any new seals or gaskets that came with the kit. Carefully lower the new assembly into the tank, aligning it correctly with the tank's mounting points. Secure it with the locking ring, tightening it firmly by hand or with the tool until it is snug.

5. Reinstall the Fuel Tank and Reconnect Everything.
Carefully place the tank back into its position in the Ace. Reconnect the fuel lines, ensuring each "clicks" and is fully seated. Reconnect the electrical connector. Reattach all tank straps and bolts securely. Reconnect the negative battery terminal.

6. Prime the System and Check for Leaks.
Turn the ignition key to the ON position and listen for the new pump to prime for 2-3 seconds. Do this 2-3 times to build full system pressure. Inspect all connections for any sign of fuel leaks. If all is dry, start the engine. It may crank slightly longer than usual as the system fully primes. Let it idle and check for leaks again. Take a short test ride to verify normal performance has been restored.

Choosing the Right Replacement Fuel Pump

When selecting a new fuel pump for your Polaris Ace 150, 500, 570, or 900, you have several options.

OEM (Original Equipment Manufacturer) Parts: These are made by or for Polaris. They offer a perfect fit and guaranteed performance but are typically the most expensive option.

High-Quality Aftermarket Brands: Brands like Quantum Fuel Systems, Delphi, and Airtex are reputable manufacturers that often supply pumps to OEMs. Their kits are usually complete with all necessary seals, filters, and locking rings, offering excellent reliability at a more competitive price. Ensure the part listing specifically includes your Ace model and year range (e.g., "fits Polaris Ace 570 2017 2018 2019").

Avoid Generic or Extremely Low-Cost Pumps: While tempting, these pumps often use inferior materials and motors. They may have a shorter lifespan, incorrect pressure output, or poor fitment, leading to premature failure and the need to do the job again.

Preventive Maintenance Tips

While fuel pumps are wear items, you can extend their life with good practices.

  • Keep Your Fuel Tank Above 1/4 Full: The gasoline submerging the pump cools it. Running consistently on a very low tank allows the pump to overheat and wear out faster.
  • Use Fresh, Clean Fuel: Stale fuel or fuel contaminated with dirt or water puts extra strain on the pump and clogs the filter sock. If storing your Ace, use a fuel stabilizer.
  • Replace the In-Line Fuel Filter: If your model has a separate, serviceable in-line fuel filter in addition to the pump's internal sock, replace it at the intervals recommended in your owner's manual. A clogged filter makes the pump work much harder.

By understanding the importance of the fuel pump, recognizing its failure signs, and knowing how to properly diagnose and replace it, you can ensure your Polaris Ace 150, 500, 570, or 900 from the 2017, 2018, 2019, 2020, and 2021 model years continues to deliver the reliable, powerful performance you expect on every ride. Always consult your specific model's service manual for the most precise specifications and procedures.


Back to blog