Polaris Sportsman 570 Cranks But Won't Start — Fuel, Spark, & EFI Diagnosis
⚡ Quick Answer
For a Polaris Sportsman 570 that cranks but won't fire, the most common culprit is a fouled NGK MR7F spark plug caused by cold-start carbon loading, or a failing fuel pump that cannot maintain the required 58 PSI. First, ensure your battery voltage stays above 10.5V during cranking, as the EFI ECU will not trigger the injectors if the voltage drops too low. If voltage is good, check for a broken T-MAP sensor wire near the intake boot, a notorious vibration failure point on this ProStar engine.
What do you want to do?
Most Likely Cause
Fuel Pump Module Failure
The internal fuel pump motor often suffers from heat soak or electrical failure. You can diagnose this by listening for the 2-second high-pitched whine when the key is turned; silence indicates a dead pump or blown fuse.
Start here — this is the most common reason for this symptom.
Why This Problem Happens
The Polaris Sportsman 570 uses a sophisticated Bosch Electronic Fuel Injection (EFI) system that requires precise synchronization between the Crankshaft Position Sensor (CPS), the Electronic Control Module (ECM), and the fuel pump pressure. When the engine cranks but fails to fire, it is usually because the combustion chamber is being deprived of one of the three critical requirements: pressurized fuel, a high-voltage spark at the correct timing, or adequate compression. Because the 570 features a 'locked-in' fuel pressure regulator within the fuel pump assembly, any degradation in pump output—even slightly below the required 40-45 PSI—will prevent the injector from atomizing fuel, leading to a dry start condition. Furthermore, the 570’s sensitive ECU logic will cut spark or fuel injection timing if the CPS signal is noisy or interrupted by metallic debris, effectively stalling the engine's attempt to cycle. This failure often manifests as a mechanical breakdown where the electrical system is functional enough to turn the starter, but the combustion cycle cannot sustain itself because the fuel delivery pressure or ignition pulse timing has fallen out of the tight tolerances required by the ProStar engine management maps.
Common Symptoms
- Audible fuel pump priming failure at key-on
- Strong smell of raw fuel after extended cranking
- Check engine light flashing during start attempt
- Backfiring through the intake plenum
- Engine fires briefly on starting fluid then dies
- Intermittent spark test result
Before You Buy Parts
Quick, free inspections — check these first. Most repairs don't actually need replacement parts.
Complete Resource Guide
Complete Side-by-Side (SxS) Troubleshooting Guide
Repair Overview
1–3 hours
$20–$150
First Checks — Start Here
- 1Check battery voltage — must be 12.6V static and 10.5V+ while cranking
- 2Listen for the fuel pump 'whir' for 2 seconds when the key is turned to ON
- 3Replace the NGK MR7F spark plug — do not just clean it, these are prone to internal failure
- 4Verify the 'Kill Switch' on the left handlebar is in the 'Run' position
- 5Check for water or sediment in the fuel tank by drawing a sample from the bottom
- 6Inspect the T-MAP sensor wiring harness for broken or stretched wires near the connector
Safety Warnings
- !Keep a Class B fire extinguisher nearby when working with pressurized fuel lines.
- !Use insulated pliers to hold the plug wire to avoid a high-voltage shock.
- !Ensure the ignition is off when testing for continuity to prevent meter damage.
- !Allow the engine to cool completely before touching the engine block.
- !Wear safety glasses to prevent chemical spray from entering your eyes.
- !Do not short the battery terminals with metal tools.
- !Replacing the fuel pump without checking the fuel pump relay first
- !Assuming the spark plug is good because it is 'new' without testing the actual coil output
Always disconnect the spark plug, work in a well-ventilated area, and consult a professional if unsure.
Most Likely Causes
Ranked by likelihood — tap each to see diagnosis details.
The internal fuel pump motor often suffers from heat soak or electrical failure. You can diagnose this by listening for the 2-second high-pitched whine when the key is turned; silence indicates a dead pump or blown fuse.
Due to the small nozzle diameter of the 570's injector, varnish from old fuel can easily plug the tip. Use a noid light to confirm the ECU is sending an electrical signal to the injector, confirming it is not an electrical circuit failure.
🔧 Step-by-Step Fix Guide
Verify Fuel Pump Prime and Pressure
Listen for the fuel pump whine upon key turn. If silent, check the fuel pump fuse; if the pump runs but the engine won't start, install a fuel pressure gauge on the fuel rail to ensure it hits 40-45 PSI.
Keep a Class B fire extinguisher nearby when working with pressurized fuel lines.
Perform a Spark Test
Remove the spark plug, re-insert it into the spark plug wire, and ground the threads against the engine head. Crank the engine and observe for a strong, bright blue spark; a yellow spark indicates a weak ignition coil.
Use insulated pliers to hold the plug wire to avoid a high-voltage shock.
Test the T-BAP Wiring Harness
Inspect the wiring leading to the T-BAP sensor located on the intake boot. Use a multimeter to check for continuity in the wires, as the vibration of the 570 often causes internal wire fractures.
Ensure the ignition is off when testing for continuity to prevent meter damage.
Check the Crankshaft Position Sensor (CPS)
Locate the CPS on the engine case, remove it, and clean the face of the sensor with brake cleaner. Use a feeler gauge to verify the air gap is within the factory specification listed in your service manual.
Allow the engine to cool completely before touching the engine block.
Clean the Throttle Body
Remove the air intake hose and inspect the butterfly valve. Clean any carbon buildup using specialized throttle body cleaner and a soft cloth to ensure the intake path is not obstructed.
Wear safety glasses to prevent chemical spray from entering your eyes.
Verify Battery Load
Even if the lights turn on, the battery may lack the cranking amps to keep the ECU awake during the start sequence. Perform a load test using a battery tester to ensure it maintains at least 10V while cranking.
Do not short the battery terminals with metal tools.
What To Test Next
If fuel delivery checks out, the next thing to inspect is spark — remove the spark plug, ground its threads to the engine block, and crank the engine to look for a visible blue spark.
Component Reference
Carburetor & Fuel Intake
The carburetor mixes air and fuel for combustion. A clogged jet or stuck float is the #1 cause of small engine starting and surging problems.
Spark Plug & Ignition System
The spark plug ignites the air-fuel mixture. A fouled plug, wrong gap, or failing ignition coil will prevent the engine from firing.
Oil & Lubrication System
Regular oil changes are critical. Low or dirty oil causes engine wear, overheating, and eventual seizure. Check the dipstick before every season.
Fuel System
Stale fuel is the most common cause of seasonal starting failures. Fuel breaks down in 30 days, leaving varnish that clogs carburetor jets and fuel filters.
Photos for educational reference. Actual parts may vary by make and model.
Common Mistakes to Avoid
Replacing the fuel pump without checking the fuel pump relay first
Assuming the spark plug is good because it is 'new' without testing the actual coil output
Ignoring the T-BAP sensor wiring which is a known 'hidden' failure point
Using starting fluid extensively, which can wash oil off the cylinder walls and reduce compression
If This Didn't Fix It
Still having trouble? These are the next things to check:
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Finding parts for
Polaris Sportsman 570
Required Gear
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Fuel Pump Assembly
If the fuel pump fails to prime or maintain proper EFI pressure, the entire module must be replaced to restore fuel delivery to the engine.
Crankshaft Position Sensor (CPS)
When the CPS fails, the ECU cannot accurately track engine timing, preventing the ignition system from firing the spark plug to start the motor.
T-BAP Sensor Wiring Repair Kit
The T-BAP harness is prone to wire fatigue on the 570, requiring a specific repair pigtail to fix intermittent sensor signals that prevent the machine from starting.
Fuel Injector
If the injector is clogged or electrically dead, it will not spray fuel into the intake, requiring a direct replacement to resolve the no-start condition.
Spark Plug
A fouled or degraded spark plug can cause a weak or non-existent spark, making it a necessary replacement item once the ignition system is deemed faulty during the spark test.
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Pro Tips from the Community
Real-world fixes from Reddit, YouTube & forums.
"If the 570 is flooded, hold the throttle wide open while cranking. This puts the ECU in 'Clear Flood Mode' which shuts off the fuel injector to help dry out the spark plug."
Reddit r/ATV"Check the wiring harness where it rubs against the frame near the starter solenoid. The 570s are known for harness rub-throughs that can short out the ECU power wire."
PolarisRiders.com Forum"The brake pressure switch must trigger for the engine to start. If your brake lights don't come on when you squeeze the lever, the ATV won't fire even if the starter spins."
YouTube commentsPrevent This From Coming Back
Use a fuel stabilizer like Sta-Bil in every tank if the ATV sits for more than two weeks
Regularly inspect the T-BAP wiring harness for signs of chafing
Replace the spark plug every 50 hours of operation
Keep the battery on a smart charger/maintainer like a Battery Tender when in storage
Prevent This From Happening Again
While you're fixing it, stock up on the maintenance essentials that keep your side-by-sides running right.
Small Engine Oil
Heavy loads mean you should change oil more frequently.
Get on AmazonAir Filter
Dusty trails clog filters — keep a spare on hand.
Get on AmazonDrive Belt
A worn CVT belt causes slipping and power loss — keep a spare.
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Frequently Asked Questions
Use it sparingly as a last resort diagnostic. If the engine fires on starting fluid, you have confirmed a fuel delivery issue, but do not spray excessively as it can damage the top end.
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