Lawnmower Hard to Start When Cold:


When working smoothly, lawnmowers can be fun to use. I find it to be some time for myself. But they can be frustrating at times as well, especially when they don’t start easily when cold. A lawnmower having trouble starting or shutting down just moments after starting are not uncommon problems. There is not a single reason behind a mower not starting. That means you need to diagnose what the cause is first and then fix the problem. It can be because you use bad gas or is it the oil makes it hard to start. Another reason can be a bad working spark plug or a malfunctioning carburetor. Starting in cold weather can be even worse with the added issues such as an increased oil viscosity. But if you know what causes a mower to not start at the first or second attempt, you can go for the correct fix. This article will provide you with necessary information on the various causes and fixes that prevent the mower from starting normally and the procedure on how to start a lawnmower in cold weather.

Lawnmower Hard to Start When Cold:

  • Insufficient or bad gas.
  • Clogged fuel lines disturbing the composition of the fuel-air mixture.
  • Clogged air filter resulting in insufficient air in the combustion chamber.
  • A faulty spark plug.
  • Wrong oil
  • A bad solenoid or starter motor
  • A dead or faulty battery

Cold weather can further add the following problems to this list:

  • Change in oil viscosity leading to reduced oil flow
  • The metal contraction that can result in valve problems

Your cold mower not starting could be because of any of the problems mentioned above. Therefore, you’ll have to check for each, one by one. Fixing most of these issues is not too difficult, and you can do it yourself. You have a basic knowledge of how the various components of a lawnmower work will surely help you.

Reasons behind a Cold Lawnmower not starting:

IF you have problems with starting your cold lawnmower, it is time to diagnose the problem and eliminate the different reasons. Often there will be one reason why it fails to start, but it is also possible that there are two reasons why this is happening. So do not stop after you found one reason.

To make your lawnmower work well now and in the future, maintenance is essential. A well-maintained lawnmower will have way fewer problems starting than one that lacks proper care. Good maintenance will also make sure your mower will last much longer and leaves a better cut lawn.

Before we dive into why a cold lawnmower is not starting, it is good to know that the current outside temperature also influences how easy a mower will start. If it is really cold, your lawnmower will be harder to start, similar to your car.

● Insufficient or Bad Gas:

The insufficient part is quite obvious. The first thing you’d do if your mower weren’t starting would be to open the fuel tank and check if the gas level is too low. If it is, top it up and trying again.

The issue of bad gas is a bit more complex. But there is a simple rule that you should remember: don’t let gas sit in the tank for too long. Gas sitting in the mower’s tank can go bad quickly because of evaporation and oxidation. The oxidation effect is even bigger in ethanol-blended gas (i.e., E10), which you most probably use. Old gas also harms the carburetor and fuel lines, causing all sorts of other problems that eventually can lead to your mower not starting.

Don’t let gas sit in the mower for more than 30 days. If there was gas sitting in the tank for that long, drain it and add fresh gas before starting. A fuel stabilizer is also an option if you do not use your lawnmower for a more extended period, like during the winter.

● Clogged Fuel Lines:

The fuel lines can get clogged by debris or by the thick varnish-like substance produced due to the oxidation of sitting gas. When the fuel-lines are blocked, fuel flow to the carburetor is disrupted, and the correct fuel-air mixture does not reach the combustion chamber. This results in incomplete combustion, which won’t start the mower.

If your mower is not starting or breaks down moments after starting, check and unclog the fuel lines.

● Clogged Air Filter:

Debris getting caught in the air filter over an extended period of use can clog the filter. With a clogged air filter, insufficient oxygen reaches the combustion chamber, resulting in incomplete combustion.

If your cold mower is not starting easily, check the air filter. If it is dirty, clean it with a brush, soap, and water. If this does not help or is filthy and clogged, replace it with a new one.

● Faulty Spark Plug:

A faulty spark plug could be one with the wrong electrode gap or dirty electrodes owing to carbon deposits and corrosion. A faulty spark plug cannot provide a strong enough spark to ignite the combustion chamber’s air-fuel mixture.

A dirty spark plug can be cleaned using a metal file or sandpaper. If a spark plug is defective beyond repair, replace it with a new one. Spark plugs are not too expensive, but you must replace your spark plug with a matching one.

If you have a sparkplug tester, use it to identify bad spark plugs. 

● Wrong Oil:

If your mower is not starting easily, it could be because the oil it is using does not match the required specifications. Oil specifications vary for different types and models of lawnmowers and also for the working environment.

Oil grades are based on viscosity—oil viscosity increases in colder weather. In simple words, it gets thicker, which reduces its flow. Single grade oils usually work in narrow temperature ranges and will have to be changed at different times of the year. On the other hand, multi-grade oil can function in a wider temperature range.

Special oils exist for cold temperature applications. So, choose the oil for your mower based on the working temperature. Consulting the manufacturer’s manual or online research can help you with the oil selection.

● Faulty Starter:

The starter is a small component between the battery and the spark plug that transfers current from the battery to the plug. It consists of the starter solenoid and the starter motor. If anyone or two of these components are defective, the current won’t reach the spark plug, and the mower won’t start.

If your mower is not starting, check the starter. You can bypass the starter if it is faulty, but replacing a bad starter would be the best option.

Check the battery too. The mower won’t start if the battery is dead or faulty.

Problems Caused by Cold Weather:

Colder working environments can cause some changes that make it hard to start the mower. Problems caused by cold weather include:

● Reduced Oil Flow:

Cold weather increases oil viscosity, reducing its flow. To avoid this situation, make sure that you are using an oil type suited to colder environments. You can also overcome this problem by increasing the oil level in your mower’s oil reservoir.

● Valve Problems:

Temperature changes cause metals to expand contract. In cold weather, metal contracts, which could lead to narrower valve passages. If this is the case, you should consult a professional mechanic for a valve change or repair.

Starting a Cold Mower:

You don’t need to be a pro to be able to start your cold mower. If the problem is not of a very grave nature, you’ll be able to start your cold mower by following the step by step procedure given below.

● Step 1:

Park your mower on an open flat area, with the parking brake engaged. Remove the spark plug using a wrench. Clean the spark plug electrode area using a file or sandpaper. Then put it back in and connect the spark plug lead to it.

Make sure that the gas in the tank is enough.

● Step 2:

Take the air filter out and inspect it. Clean it off any debris using a screwdriver or by washing it. Then put it back on.

● Step 3:

Press the primer button three times, waiting for it to come back out before the next press.

● Step 4:

Pull the starter cord to start your mower. You may have to pull the starter cord more than once.

Final Remarks:

It can be challenging to start a cold lawnmower due to several possible reasons. If you are faced with a mower not starting easily, eliminate the possible causes one by one. Some problems are related explicitly to cold working temperature and will need to be taken care of. Most issues that prevent a mower from starting easily are not too dangerous and can easily be fixed. All in all, don’t let your cold, difficult to start the mower from ruining your mood. Follow the guidelines mentioned in this article to get your cold mower running.

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