John Deere Lawn Mower Only Start While the CHOKE Engaged

If too much air or not enough gasoline is being allowed into the engine, a John Deere lawn mower may only start with the choke engaged.

A clogged or punctured fuel line, a damaged fuel pump, a faulty fuel filter, a faulty gas cap, or a faulty carburetor gasket could all contribute to this problem.

For more information on how to operate safely with your John Deere, consult the manual. Before beginning maintenance, make sure the ignition is turned off and the spark plug boot is removed.

John Deere Mower

Before attempting any diagnosis, repairs, or use of the equipment, be sure to read and fully understand the operator’s manual. If you don’t feel confident in your ability to conduct the repair safely on your own, it’s best to call in an expert.

7 Causes John Deere Mower Won’t Start Without the Choke

Using Old Gas

The shelf life of gasoline is rather short. As soon as a month or so after purchase, it may start to malfunction. The fuel system may jam up and components will rust if old gas is used.

Ethanol, a type of alternative fuel, is now present in nearly all gasoline on the market. Although this product is safer for the planet, it can damage smaller engines like the one found in a John Deere.

Water vapor in the air is drawn to ethanol, making the fuel more humid. The ethanol and water will naturally settle to the bottom of the tank with the gasoline.

This combination causes the engine to overheat and leaves behind sticky deposits when it evaporates. Water is corrosive and can ruin mechanical parts of fuel systems.

Inadequate fuel delivery to the engine can be caused by a number of factors, including faulty fuel system components and buildup of debris. To maintain engine operation, the choke may need to be used to adjust the gas-to-air mixture.

Mowers manufactured by John Deere call for unleaded gasoline with an octane value of 87 or above and no more than 10% ethanol. Never fill up with fuel that has more than 10% ethanol in it.

The ANSWER is to get rid of the stale gas in the tank. To clean and minimize moisture in the fuel system, put in new gas with a fuel additive like Sea Foam Motor Treatment or STA-BIL.

It will also prevent the gas from destabilizing as quickly, extending its useful life. Learn the reasons why I use Sea Foam in all of my portable motors.

John Deere Lawn Mower with a Filthy Carburetor

A carburetor controls the ratio of fuel to air in an internal combustion engine. Fuel passages and internal parts might become clogged and nonfunctional when it becomes unclean, most frequently owing to old gas.

In order for the engine to perform smoothly, the carburetor will need to be serviced or changed.

The carburetor of your John Deere mower may be removed and cleaned with a little technical knowledge and a tolerance for fiddly tasks.

After following these instructions to clean the carburetor, if it still doesn’t function, you may need to rebuild or replace it. If you don’t feel comfortable cleaning or rebuilding the carburetor, have a small engine mechanic do it for you.

Damage to or Blockage of John Deere Mower’s Fuel Line

Too much air might be sucked into the fuel line and into the engine if the line gets punctured. Or, a blockage in the line could form, reducing the fuel supply to the engine.

Either of these problems can make the mower inoperable except with the choke engaged, as the latter is necessary to regulate the quantity of air entering the engine in order to achieve the correct fuel-to-air ratio for combustion.

Checking the fuel lines is the solution. Find the fuel line’s exit point and trace it to the carburetor from there. Check for holes or rips that could let air into the gas tank.

Next, examine the fuel line for obstructions that could reduce fuel flow. The fuel shut-off valve must be used first to stop the fuel supply. Then, cut off a length of the gasoline line and set the cut end in a suitable collection vessel.

After resuming fuel flow, make sure fuel is flowing freely from the fuel line and into the storage tank. Turn off the gas and disconnect the fuel line from the mower if the flow is poor.

Carburetor cleaning can be sprayed into the line to help break up the obstruction. The next step is to use compressed air to blow out the obstruction. When necessary, the process can be repeated.

If the gasoline line is too clogged or damaged to be cleaned, or if you locate a puncture, you should replace the damaged portion with a new one of the same diameter.

John Deere Mower Fuel Filter Clogged

To clean the fuel as it leaves the fuel tank, an inline fuel filter is installed between the fuel lines. This will prevent debris and other debris from entering the gasoline tank and wearing it out.

This is a wearable part that needs to be replaced every year. If the gasoline filter gets clogged, it could reduce the fuel flow to the engine.

To fix this, take out the clogged filter and replace it with a new inline fuel filter.

On the side of the filter housing, you should see an arrow. When installing the filter, make sure the arrow points in the direction of fuel flow.

John Deere Mower with a Bad Fuel Pump

Your John Deere mower has a fuel pump to help push gas to the top of the engine, where the carburetor is located. Today’s mowers rely on vacuum pumps. The fuel is pumped from the tank to the carburetor using the engine’s exhaust vacuum.

Verify that fuel is entering the pump’s inlet port when performing a fuel pump test. The next step is to test the fuel flow by disconnecting the fuel line from the carburetor and placing it in a container.

A new fuel pump should be installed if insufficient fuel flow is being delivered or if fuel leaks are discovered.

John Deere Mower with a Leaky Carburetor Gasket

The John Deere carburetor’s gasket may become damaged with time, rendering it unable to maintain a tight seal. If the gasket is leaking, the engine will run too lean because extra air is being sucked into the system.

To be “running lean” means that the ratio of air to fuel in the engine’s combustion chamber is higher than normal. If the engine is sucking in too much air due to a faulty gasket, you’ll need to adjust the choke accordingly.

Make sure the carburetor’s gasket is in good shape and that all bolts are properly fastened.

If the gasket is no longer sealing, you can get to the carburetor by dismantling the supporting linkages and nuts. The gasket and carburetor must be taken off.

After replacing the gasket, the carburetor, bolt, and links can be reattached. While the carburetor is out of the mower, you can inspect it to see if it needs to be cleaned.

John Deere Mower Gas Cap Problem

The gas tank must have a way for fresh air to enter it. When the vent is blocked, no air can enter the fuel tank, creating a vacuum. Due to the absence of air, the fuel supply cannot reach the carburetor.

The gas cap serves as a vent for the fuel tank. To determine if there is a vacuum buildup, you can use a pressure gauge or the following procedures:

  • The gas tank needs air, so loosen the cap.
  • Choke should be turned all the way off.
  • If the engine keeps running with the choke turned off, the cap could be malfunctioning.
  • You should attempt a replication of the situation to verify the bad cap.
  • Put the top back on and let the motor keep running without the choke.
  • If the engine sputters after a while and won’t run smoothly unless you unscrew the cap, it probably has a faulty cap.

FIX: Get a new gas cap.

Are You Still Experiencing Issues with Your John Deere Mower?

There are a wide range of issues you may face as a John Deere mower owner. Some of these issues include starting, shutting off mid-mowing, vibrating excessively, cutting unevenly, and not moving at all.

I compiled a useful guide for diagnosing issues with your John Deere mower so you can figure out what’s wrong with it. Read “Common John Deere Lawn Mower Problems and Solutions