7 Symptoms of a Bad Fuel Shut off Solenoid

Symptoms of a Bad Fuel Shut off Solenoid

The problem with a bad fuel solenoid is that if you are not experienced, you may not know the source of the problem.

Some of the components you may suspect are problematic include filters and fuel lines. In some cases, you may blame it on bad fuel.

But if you are an experienced mower operator, you will easily tell that the problem is a bad fuel solenoid. Doing so will save you time and allow you to look for appropriate solutions.

Of course, there are tell-tale signs that your mower has a bad fuel shut-off solenoid. Keep reading to learn in-depth about the symptoms of a bad fuel shut-off solenoid and what you may need to do to fix the problems.

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What Does A Fuel Shut-Off Solenoid Do?

The function of the shut-off fuel solenoid is to interrupt the fuel flow from the injection pump when you switch off the ignition.

It consists of a valve that cuts the fuel supply to the engine. Also, the solenoid valve stops the engine from backfiring and getting flooded when the jets start leaking.

On activation, the solenoid draws a higher current from the batteries, which magnetizes the coil and pulls the solenoid plunger.

The action opens the valve to allow fuel into the carburettor.  When you turn the off the ignition, the valve spring pulls sealing surface down, stopping the fuel from getting into the carburettor.

Typically the fuel shut-off solenoid acts like a switch that shuts off the fuel pump when you remove the ignition key and opens it when you turn the ignition.

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Bypassing The Fuel Solenoid

To bypass a bad fuel-shut solenoid, start by fitting a valve on the carburettor fuel inlet line. Once done, shut off the valve and use a wrench to remove the solenoid from the carburettor.

Let the fuel that had accumulated in the carburettor drain off. You will then remove the sealing surface on the plunger so that it can allow fuel to flow into the combustion chamber uninterrupted.

This sealing surface on the plunger stops fuel from entering the combustion chamber.

So when you remove it, the fuel flow into the engine uninterrupted until you shut off the artificial valve fitted on the fuel line.

7 Symptoms of a Bad Fuel Shut off Solenoid

The symptoms of a bad fuel solenoid include the engine stopping or suddenly, a switch that trips, and an engine that stalls.

Also, it may disable the fuel pump leading to a no-start condition that makes it hard for the engine to start.

1. Engine Shutting Off

The mower engine runs on fuel. So if the bad fuel solenoid disrupts the fuel flow, the engine shuts off.

This happens whenever the solenoid loses the electromagnetic and reverts to the off position starving the engine of fuel.

So the engine may stop running while the mower is moving. Thus, when the solenoid malfunctions, it stalls the engine.

How it works

Connecting the fuel shutoff solenoid lose end to a battery enables the coil to generate a strong magnetic field. The field pulls the solenoid plunger toward the coil’s direction.

It lifts the poppet causing the valve to rise and allow fuel to flow into the carburetor. It stops fuel from getting into the carburetor when you turn off the ignition.


If you suspect the cause of the issue is a malfunctioning solenoid. You may need to troubleshoot it to determine if it opens and closes to control fuel flow.

You’ll need a 12-volt battery, a vice, a wrench, and connecting wires to troubleshoot the bad fuel shut-off solenoid.

Use a wrench to remove the solenoid from the carburetor. Here’s where to find the carburetor in your mower.

Once it is done, clamp it into the vice and connect the battery to the positive side of the solenoid.

Touch the other wire on the negative side of the solenoid. You should see the solenoid rubber pole move up and down. If it does not, the solenoid is defective


  • If the solenoid works, reactivate the fuel pump or reset the button switch. If it is not working, consider replacing or bypassing it.

2. Smoke

Because of a bad fuel shut-off solenoid, you may see smoke coming from the engine. Also, you may experience some noise followed by a slow acceleration.

Luckily, you may not experience this problem if your mower is fitted with the latest engine. However, if the mower runs on an old engine, expect to experience the problem often.

Too much smoke from the engine means the solenoid is defective or the valves are faulty. When the valves are faulty, they allow too much fuel into the carburetor.

Typically, a solenoid poppet valve comprises an orifice that opens and shuts by raising and lowering the sealing surface into the orifice.

The solenoid has an internal spring to hold the valve in a closed position. But when ignited, the solenoid coil gets magnetized and lifts the sealing surface to open the valve.

Therefore, if the solenoid is not working, it may cut off the fuel supply or allow excess fuel into the combustion chamber. Burning too much fuel makes the engine release smoke.


Clean fuel filters, and top up the oil and refill the gas tank. Start the mower and let it burn the excess oil for 5 minutes.

If the smoke does not go away, then it’s a case of a bad solenoid.


  • There is little you can do to sort out this problem besides replacing the solenoid.

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3. Unsteady Idling

It is good manners to warm the engine for a few seconds before using it. Unfortunately, the engine may die off during the idling stage.

It will do this while producing some peculiar sound that lets you know there is a problem.

Typically, this will happen if the engine gets energized but switches off because of the damaged solenoid. So when little or no fuel enters the combustion chamber, the engine dies off.


Clean the air filters, and fuel injectors and replace the spark plug. If idling does not improve, check the fuel-shut solenoid.


  • Replace the defective solenoid

4. Cold Start

When the solenoid is faulty, it becomes difficult for the engine to start because no fuel enters the combustion chamber.

If the engine is cold, you will see it struggling to move fuel to its combustion chamber. Also, you will notice the engine taking longer than it usually does to start running.

The fuel shutdown solenoid requires a lot of current to energize the coil and pull the solenoid plunger. Once it pulls the plunger, it allows fuel to flow into the combustion chamber.

So overnight, the battery experiences a voltage drop, so it may not start the mower in the morning.


To troubleshoot the cold start problem, switch off the engine and power it again. If it does not start, use a multimeter to test the battery voltage.


  • Replace the battery
  • Clean the plunger and ensure the rubber boot is not torn and does not get in the way

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5. Rushing Noise

If the tractor produces a buzzing sound when you start it, you may need to check the solenoid. Typically, the rushing sound will only last for a short time.

Moreover, it will only hear it when starting the engine. Of course, the noise is annoying and could upset you. Therefore, you should fix it before it completely shuts down the engine.


Turn the ignition key and listen to the peculiar buzzing sound it produces


  • Get the solenoid cleaned to see if it fixes the problem.
  • Open the panel and check for loose solenoid connections.
  • Replace the solenoid.

6. Trouble When Accelerating

The solenoid may fail when in the on/off position or stick in the halfway position. If it sticks in the halfway position, the idling may be fine and will operate normally at slow RPM.

But if you try to put it under maximum RPMs, it starves of fuel and will hesitate to accelerate. This is a tell-tale sign that the mower has a bad solenoid.


Remove the solenoid and connect it to a power source to see if the solenoid plunger is working.


  • Replace the bad fuel shut off solenoid.

7. The Valve Does not Open or Close

Corrosion, rust, power failure, and dirt stuck in the solenoid system may make it hard to open and close.

Unfortunately, there are many reasons why a solenoid fails or why the solenoid may not open or closs correctly.


Remove the solenoid and connect it to a battery to see if it moves the solenoid plunger.


  • Check the power supply to ensure it supplies the correct voltage and current.
  • Check and ensure connections are properly made.
  • Clean the system to remove dirt and corrosion.
  • Replace the solenoid.

Table of Symptoms /Detection

1. Engine shutting offEngine stops running
2. SmokeSmoke coming from the engine
3. Unsteady idlingEngine dies off
4. Cold startEngine management system takes long to start
5. Rushing noiseProduces buzzing sound
6. Trouble when acceleratingSlows down when under maximum RPM
7. The valve does not open or closeEngine doesn’t stop when you remove ignition/engine doesn’t start when you turn ignition

Carburetor Solenoid Malfunctioning Symptoms For Different Brands

The symptoms for malfunctioning shut-off solenoids vary from one brand to another.

Here is a summary of the symptoms for Kohler, John Deere, Kawasaki, Craftsman, and Briggs and Stratton carburetor problems.

Kohler, bad fuel shut off solenoid symptoms

The electric starting system in Kohler engines for lawnmowers includes key components like a starter solenoid.

This solenoid regulates how much fuel gets to the engine and could be a source of Kohler fuel pump complications.

When the solenoid shuts off the supply, it is difficult for the ignition key to start the engine. So the engine refuses to start when the ignition is turned on.

John Deere fuel shut-off solenoid problems

The solenoid features a spring-loaded puppet that gets pulled to allow fuel to flow to the engine. When it is turned off, it stops the flow of fuel.

The problem with the solenoid is that it shuts off when you start the tractor. Also, it may break when the engine enters running mode.

The fuel shut-off solenoid may refuse to open or lose its two-way function to start or stop the mower from running.

Briggs and Stratton fuel solenoid problems and troubleshooting

Briggs and Stratton fuel solenoid may refuse to work after some time. This could happen when the rubber is worn out or the battery is old.

An old battery may not provide the current required to magnetize the coil and pull the solenoid plunger to allow fuel to flow into the carburetor.

To troubleshoot the problem, use a wrench to remove the solenoid and connect it to a 12-volt source.

If it pulls the solenoid plunger, the problem may be elsewhere. If it does not, then replace your charging system or the solenoid.

Kawasaki fuel shut off solenoid bypass process

When the Kawasaki fuel shut solenoid is bad, you may need to replace it or bypass it. To bypass the solenoid, start by removing it from the system.

Secondly, fit a valve on the inlet pipe and close it. Use a wrench to remove the solenoid and give the carburetor 5 minutes to drain.

Remove the rubber pole on the solenoid and return it to its original position. The solenoid will allow fuel to flow to the combustion chamber without hindrance.

Craftsman riding mower carburetor solenoid symptoms

The most common craftsman carburetor solenoid symptom is where the engine starts, stops, and starts again.

If this happens, again and again, you need to replace the solenoid. Typically, a bad solenoid will not have the power to pull the solenoid plunger when the ignition key is turned on.

It shunts and starves the engine of fuel hence preventing it from starting. The causes include low battery voltage and electrical connection issues.

How To Test A Fuel Shut-Off Solenoid

Testing a fuel shut-off solenoid is a simple process but could be a nightmare if you do it for the first time. You need a wrench, a vice, a 12-volt source, and connecting wires.

Remove the solenoid from the carburetor using a wrench. Once done, clamp the solenoid on a vice and connect the wires to the battery.

Connect the positive side of the battery on the solenoid and the negative side to the other terminal.

The rubber pole should move up and down. The solenoid works if it moves up and down as you disconnect and disconnect.


Why would a lawn mower solenoid keep going bad?

There are many reasons why your mower solenoid could be going bad. Firstly, leaving the ignition in the start position could cause a problem.

What happens is that the solenoid gets damaged as a result of allowing current to flow through it for a long. So if there is overheating, the solenoid will go bad. Other causes include poor wiring and excessive moisture.

Will a bad solenoid drain battery on a lawn mower

If the solenoid is bad, it will not drain the battery; however, if the regulator is faulty or the wires are corroded, they will likely drain the battery. Also, solenoid corrosion could result in short-circuiting and may drain your battery.

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How to tell if the solenoid is bad on a lawn mower

A bad solenoid is likely to cause many problems.  It may make your mower refuse to start or start and stops. It could also make the mower engine die when running. Also, listen to the mower if no sound comes from it or it produces a rushing or buzzing sound, it could be faulty.

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Final thoughts on symptoms of a bad carburettor solenoid

The symptoms of bad solenoid problems are many and varied. They range from the engine refusing to start or stopping as soon as it starts.

You may also observe smoke from the engine or the mower slowing down at maximum RPM. Thus, you may need to troubleshoot it severally to help you confirm the problem.

Removing the solenoid and connecting it to a source of power could thus help you confirm fuel shutoff solenoids lose problem.