Cub Cadet Zero Turn Cranks But Won’t Start

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If your Cub Cadet Zero Turn mower cranks but won’t start, it can be caused by issues with the fuel delivery, air supply, ignition, or electric system.

Fortunately, these issues are usually easy to fix once you identify the cause.

I talk about the reasons your Cub Cadet Zero Turn cranks but won’t start, and also outline practical troubleshooting steps to diagnose and fix these issues.

Reasons Why Your Cub Cadet Zero Turn Cranks But Won’t Start

Your cub cadet zero turn mower may crank but won’t start due to one of the following:

  • Clogged air filter
  • Worn spark plug
  • Clogged fuel filter/fuel line
  • Stuck fuel solenoid
  • Bad fuel pump
  • Battery issues
  • Malfunctioning safety switch
  • Sheared flywheel key
  • Faulty starter solenoid

Tools You Need For This Job

Some tools you may need for this job include:

  • Work gloves
  • Screwdriver
  • Pliers
  • Multimeter
  • Siphon
  • Clean rag
  • Wrench set

Cub Cadet Zero Turn Cranks But Won’t Start: Causes, Diagnosis, and Fixes

1. Clogged Air Filter

A dirty air filter that is blocked and is preventing the engine from receiving air could be the cause of a cub cadet that cranks but won’t start.

The carburetor requires air to effectively create the fuel-air mixture that is fed into the combustion chamber and used to power the engine.

Your cub cadet lawn mower may crank or turn over when there is inadequate air coming from the filter, but it won’t start.

Diagnosis:

Remove the air filter housing and look at the filter. It may be clogged if it is dirty or covered in dust and debris.

Fix:

Replace or clean the air filter. Before installing the replacement filter, clean the air filter housing to get rid of any leftover dust or dirt.

2. Worn Spark Plug

The spark plug is the next part you should examine if your cub cadet zero-turn cranks but won’t start.

The mower will not start if you have a worn-out or fouled spark plug in it. This is because the plug will fire irregularly or won’t produce enough spark.

A spark plug may also cause starting problems if the gap is inadequate, it is broken, or the spark plug wire is loosely connected.

Diagnosis: 

Disconnect the spark plug wire and check the spark plug for wear, rust, burnt electrodes, and carbon buildup.

Fix: 

Replace the worn-out spark plug and tightly attach the plug wire to the plug for a secure connection.

3. Clogged Fuel Filter/Fuel Line 

The fuel filter and fuel lines of your cub cadet may be blocked with debris if it cranks but doesn’t start.

The most frequent reason for clogged fuel parts is leaving stale fuel in a zero turn lawn mower and using it to run the engine.

Some of the fuel’s components evaporate over time, leaving behind a thicker, stickier material. 

This gummy fuel might block the fuel tank outlet, fuel lines, or the fuel filter and make it difficult for the engine to start. 

Diagnosis:

Check the fuel flow rate by removing the fuel line end at the carburetor. The line is clogged if the fuel is pouring slowly or not flowing at all.

Use your pliers to remove the fuel filter. Turn it around and examine the fuel flow from either side. It is clogged if it is slow or the clear fuel filter container is dirty.

Fix:

Drain stale fuel from the fuel tank and clean the fuel tank outlet. Then, replace clogged fuel filters and fuel lines with new ones.

4. Stuck Fuel Solenoid 

The fuel solenoid is a silver piece located right under the carburetor. The solenoid has a plunger in it that opens up to let gas flow. 

When old gas sits in the mower for too long and is used to run the engine, the plunger may get stuck and cause starting issues in your cub cadet.

Diagnosis:

Use a wrench to remove the solenoid attached to the carburetor. A worn solenoid plunger will not pop back up after depressing it.

Fix: 

Use the end of a screwdriver to tap the solenoid a little bit without using too much force while cranking the engine with the starter key.

If this doesn’t work, unscrew the fuel solenoid and clean it. Use a carburetor cleaner or WD-40 spray to clean and loosen up the plunger. Then let it dry and install it back to the carburetor.

5. Bad Fuel Pump 

A bad fuel pump will cut off fuel flow to the carburetor. This may be the reason your Cub Cadet Zero Turn mower cranks but won’t start.

Three ports are present on the fuel pump: the pulse port, the gas in port, and the gas out port. A little rubber tube joins the engine crankcase to the pulse port.  

Oil can enter the pulse port line through the crankcase if the engine oil is overfilled, which will stop the pulse port from functioning properly. 

Additionally, the pump has check valves that can wear out over time.

Diagnosis:

Test the fuel pump to see if it is allowing fuel into the fuel lines from the tank.

Check the pulse port line, valves, and diaphragm within the pump to see if the fuel pump is broken. 

Fix:

The fuel pump should be replaced if it is not functioning properly.

6. Battery Issues 

Battery issues can cause your Cub Cadet zero-turn mower to crank but not start.

The battery terminals might be corroded making the battery send less power to the spark plug and mower engine. A dead battery will also cause this problem to occur.

Diagnosis:

Use a multimeter to check the number of volts the battery is producing. If it is less than 12 volts, the battery is dead.

Fix:

Recharge/replace the battery if it is dead. Clean the battery terminals and connect the cables firmly to the battery.

7. Malfunctioning Safety Switch

The mower’s safety switch serves as a kill switch. It sends signals to the ignition system to shut down the mower if it detects a fault which causes the engine to shut down. 

If it becomes faulty, it may send the incorrect signal. This is usually the case if the engine cranks but does not start or if it cranks briefly but then shuts down.

Diagnosis: 

Perform a safety switch test with a multimeter. One side of the switch should produce a circuit, while the other side should be grounded.

Fix:

Check all the safety switches in your Cub Cadet mower and fix/replace any faulty switch.

8. Sheared Flywheel Key 

The flywheel key is a little piece of metal that slides into the crankshaft and connects to the flywheel. 

The flywheel key snaps in half if the lawn mower motor suddenly shuts off after running into a hard object to protect the engine. 

A broken flywheel key may prevent your cub cadet zero turn mower from starting for safety reasons. 

Diagnosis:

Inspect the flywheel key after removing the flywheel from the engine to see whether it is broken. 

Fix:

Replace the broken flywheel key.

9. Faulty Starter Solenoid 

The starter solenoid connects the starter motor directly to the battery. 

The mower won’t start if the solenoid is broken. 

When the mower is started with the ignition key, the solenoid creates a high-current electrical connection between the battery and the starter motor. 

A broken solenoid valve stops the starter motor from carrying its full electrical load, making it impossible to start the lawn mower. 

If you hear a clicking sound when you turn the starter, the solenoid may be faulty or damaged.

Diagnosis:

  • First, locate the solenoid. The solenoid is a small black box that is wired directly to the battery via a thick red wire. Locate that wire and follow it to the solenoid. 
  • A solenoid has two large posts. The red wire is connected to one, and a wire leads off to the starter right next to that post. 
  • With your insulated screwdriver, bridge the gap between the posts. 
  • If you make contact and the starter spins, the solenoid is bad; if the starter does not spin, the starter is bad.

Fix:

Replace the starter solenoid if it is bad. Replace the starter if it does not spin after performing the test.

Conclusion

The reasons your Cub Cadet zero turn mower cranks but won’t start may include: a dirty air filter, worn spark plug, fuel restrictions, battery issues, faulty starter solenoid, or a sheared flywheel key.

To get your mower operating again, take some time to examine the various parts and apply the recommended fixes outlined in this article.