01
May
2025
Troubleshooting Common Jet Ski Starting Issues
It’s a frustrating moment—you’re ready to hit the water, you press the start button on your jet ski, and while it cranks (meaning the engine is turning over), it simply won’t start. What gives?
A jet ski cranking but not starting can stem from several causes—some simple, others more mechanical. In this blog, we’ll break down the most common reasons why this might happen, and how to troubleshoot them safely and effectively.
Even if your jet ski cranks, a battery that’s low on voltage might not have enough power to fire the ignition system or fuel injectors.
Cranking is slow or weak
Electrical components behave erratically (e.g., lights dimming)
You haven’t charged or replaced the battery recently
Fix: Test your battery with a multimeter. A healthy 12V battery should read around 12.6V when fully charged. If it’s below 12V, recharge or replace it.
If your jet ski isn't getting fuel, the engine won’t start—regardless of how much you crank it.
Empty fuel tank (it happens!)
Old/stale fuel (fuel degrades over time)
Clogged fuel filter
Failing fuel pump
Fix: Make sure there’s fresh fuel in the tank. If the fuel is old (older than 2–3 months), consider draining and replacing it. Check for clogged filters or signs of fuel pump malfunction.
A jet ski engine needs a strong spark to ignite the air-fuel mixture. Worn or fouled spark plugs are a common culprit for no-start conditions.
Plugs appear black, oily, or corroded
No spark when tested
Fix: Remove and inspect the spark plugs. If they’re dirty or damaged, replace them. Also, check that the ignition coils and wires are properly connected and functioning.
A flooded engine happens when too much fuel enters the combustion chamber and drowns the spark, making it difficult to start.
Strong fuel smell
Engine cranks quickly but doesn’t catch
Repeated starting attempts without success
Fix: Try holding the throttle wide open (WOT) while cranking—this tells the ECU to cut fuel delivery. After a few seconds, stop and try a normal start.
Modern jet skis use electronic control units (ECUs) and sensors to manage engine functions. If the ECU malfunctions or a sensor (e.g., crankshaft position sensor) fails, it can prevent proper ignition or fuel injection.
Fix: These issues often require a diagnostic scan tool that reads fault codes from the ECU. A certified technician or dealership can help pinpoint the problem.
Most jet skis come with safety mechanisms like kill switches or lanyards (the cord you clip to your wrist). If the lanyard isn’t properly attached, the jet ski may crank but won’t start.
Fix: Make sure the kill switch lanyard is securely connected. Some models also have throttle or brake position sensors that prevent starting if not in the right state.
Jet skis need proper air flow for combustion. Blocked air intakes or water intrusion into the exhaust can interfere with engine operation.
Fix: Check air filters and intake hoses for blockages or moisture. If water has entered the engine or exhaust, it may require immediate service to prevent damage.
If your jet ski engine has low compression in one or more cylinders, it may crank without ever starting. This could be due to worn piston rings, cylinder damage, or valve problems (in 4-stroke engines).
Fix: Compression testing will confirm if this is the issue. Unfortunately, low compression usually means internal engine repairs are needed.
A jet ski that cranks but won’t start is often fixable with some basic troubleshooting. Start with the simple stuff—battery, fuel, spark plugs—and move toward more complex areas if those check out.
If you're not comfortable performing diagnostics yourself or if the problem persists, it’s best to have a certified marine mechanic take a look. Ignoring the issue or guessing can lead to more serious (and expensive) problems down the line.
If you're located in the Sarasota, Venice, Lido beach or Bradenton area and want expert help diagnosing and fixing your jet ski, don’t hesitate to reach out to JA Jet Ski Repair—your trusted local jet ski repair specialists.