How to fix a plastic gas tank on a lawnmower, step by step


Most lawnmowers use a gas engine. They make the machine powerful with high endurance. If the tank is empty, you refill and continue. However, sometimes the plastic gas tank that contains the gas may get cracked. It can be hit by something, but the gases released by the fuel weaken the tank’s walls as well. This makes it more vulnerable to a crack over time.

Cracks can result in fuel leakage that can be hazardous. But a plastic gas tank can be fixed reasonably quickly and easily at your home.

How to fix a plastic gas tank on a lawnmower, step by step:

  • Step 1: Remove the fuel out of the gas tank
  • Step 2: Detach the gas tank from the lawnmower
  • Step 3: Locate the crack on the gas tank
  • Step 4: Clean the area around the tank
  • Step 5: Fill the crack with melted plastic, or use glue or fiberglass
  • Step 6: Reattach the fixed tank to the lawnmower
How to fix a plastic gas tank on a lawnmower, step by step 1
(CC BY-SA 2.0) by steevithak

We recommend going through the entire article as all the details to the before-mentioned steps are discussed in more detail underneath.

Materials Required:

The following materials will be required to assist you in fixing the plastic gas tank efficiently and successfully:

  • Soldering iron
  • Hacksaw
  • Screwdriver
  • Safety goggles
  • Protection gloves
  • Sandpaper

Step 1. Remove all the fuel out of the gas tank:

Step 1. Park the mower at a suitable location: Park the lawnmowers at a place that can deal with some gas spillage. When you remove the gas tank, it is always possible that some of the fuel spill on the ground.

Step 2. Remove the gas: Remove the gas tank’s cap. Empty the gas tank by disconnecting the fuel line. Another method would be to siphoning the gas from the tank. Make sure that that all the gas is entirely removed from the tank.

Step 2: Detach the gas tank from the lawnmower:

Step 1. Remove the gas tank: The gas tank is attached to the lawnmower’s body with some screws. Remove these screws with the help of a screwdriver, and detach the gas tank.

Step 2. Remove the fuel fumes from the tank: The fuel fumes also need to be removed entirely from the gas tank before starting the main procedure. Take an air compressor pipe and blow air inside the gas tank. This shall remove all the fumes from the gas tank.

The gas tank’s cap should remain removed during the entire process of the tank’s fix. This is done to avoid the creation of any internal pressure inside the tank.

Step 3. Locate the crack on the gas tank:

Step 1. Fill the gas tank with some water: In most cases, you will spot the crack easily. But when this is not the case, close the hole at the bottom connected to the fuel line. Fill the gas tank with water, and keep filling the tank until you spot the leakage point. If that does not work, you can try to increase the tank’s pressure with some help from an air compressor. Use some cloth to decrease the air leakage near the fill cap.

Step 2. Mark the leakage point: Mark the area around the leakage point or the crack using a marker.

Step 3. Remove the water from the gas tank: Remove the water you just used to find the crack from the gas tank, and let it dry.

Step 4. Clean the area around the crack:

Step 1. Position the gas tank on a flat surface: Place a wooden plank or something else below the gas tank, and position it in such a way that the crack faces towards you.

Step 2. Polish the crack’s surface: Grab a small piece of sandpaper and polish the crack so that the crack’s surface becomes even and it becomes more visible.

Step 3. Clean the area around the crack: You need to use soldering iron on the area around the crack, so that area must be clean. Clean the area around the crack by putting some rubbing alcohol on a cotton swab.

Step 5. Fill the crack:

There are three possible methods to fill the crack and, thus, fix the gas tank, depending upon the crack’s size and the thickness of the tank’s walls. All methods will be discussed in more detail below.

– Method 1. Melt the area around the crack using a soldering iron:

This method is used when the gas tank is made from thick plastic. Make sure that the plastic can be melted by trying it on a small part first. See if it indeed melts, and when dried, gets its strength back. When this looks ok the step-by-step procedure to use this method is as follows:

Step 1. Switch on the soldering iron: Switch on the soldering iron, and wait until it’s heated. If the soldering iron can be set at different temperatures, start with a low temperature first.

Step 2. Melt a small trench using the soldering iron: Melt a small trench on the crack in such a way that the soldering iron doesn’t go through the tank; instead only melts the surface.

Step 3. Scoop the plastic into the trench: Now, melt some plastic surrounding the trench, and use a small tool to push this melted plastic into the trench and the crack. Keep doing this until the groove is filled with melted plastic completely.

Step 4. Recheck for any leakage: Fill the fixed gas tank with gasoline, and close the tank’s cap. Shake the tank and check if the leakage exists. Let us tell you something; you won’t see any leakage if you have applied this method step by step.

– Method 2. By melting a small piece of plastic into the crack:

This method can be used when your gas tank doesn’t have thick plastic walls. The step-by-step procedure to apply this method is as follows:

Step 1. Cut a tiny piece of plastic: Some gas tanks have additional plastic around the area of screw holes. Using a hacksaw, cut a small piece of plastic from this area. If extra plastic isn’t available on the gas tank, you may cut a tiny piece from any other thing at your home, which isn’t of any use to you.

Step 2. Switch on the soldering iron: Switch on the soldering iron, and wait until it’s heated.

Step 3. Melt the cut piece into the crack: Place the tiny plastic piece you have just cut on to the crack. Now using a soldering iron, melt this piece, and force the melted plastic into the crack. Keep doing this until the crack is filled with melted plastic.

Step 4. Recheck for any leakage: Fill the fixed gas tank with gasoline, and close the tank’s cap. Shake the tank and check if the leakage exists. But we bet that you won’t see any leakage if you have followed the steps mentioned above correctly.

– Method 3. Use glue or fiberglass to fill the crack:

If melting plastic does not work well in your case, you can fill the crack with something else. You can try to use a glue that can cope with gas. Another material would be fiberglass. Clean the environment from the crack well, and use sandpaper to roughen the area. Then use glue or fiberglass to repair the crack.

Step 6. Reattach the fixed gas tank to the lawnmower:

  • Since the gas tank has been fixed now, so it’s time to attach it back to the lawnmower
  • Tighten the gas tank screws using a screwdriver to put the tank back in its original place
  • Reconnect the fuel line to the gas tank’s nozzle

You have now successfully fixed the lawnmower’s plastic gas tank and can fill in the fuel without worrying.

Related Questions:

1. How can I tell if there is water in my lawnmower’s gas tank?

  • Left in the rain: The presence of water in the gas tank is one of the main reasons which halts the lawnmower from starting. It may not be only because the lawnmower was left out open in the rain but also because the gas in the tank condenses, thus creating moisture.
  • Sudden stall: One of the water-contaminated fuel indications is that the lawnmower suddenly stalls during its operation.
  • Smoke from the engine: Another indication is the emittance of a comparatively more significant amount of smoke from the lawnmower’s engine, resulting from low fuel combustion inside the piston chamber.
  • Check with a flashlight: A flashlight can also check the presence of water inside the gas tank. Take the lawnmower in a shady area or indoors, and then shine the light on the tank. Water being heavier than fuel, settles at the tank’s bottom and forms tiny bubbles. These bubbles can easily be spotted with the help of light.
  • Drain the gas: Such contaminated gas must be drained from the gas tank immediately, as water can corrode the engine and carburetor’s metallic parts. After the drainage of water-contaminated fuel, dry the gas tank completely using compressed air.
  • Keep the gas cap closed: It is also advised to keep the gas tank’s cap closed to avoid the entrance of any moisture inside the tank.

2. Why is my lawnmower isn’t getting any gas?

There might be multiple reasons that stop the supply of fuel to the lawnmower. A few significant causes, along with their solution, are mentioned below:

  • Check for cracks: First of all, you need to check the gas tank for any breakage or cracks. The cracks cause fuel leakage, and thus the lawnmower can run out of fuel within minutes. You need to fix the gas tank or buy a new one in this case
  • Clogged filter: Another reason that may cause this issue is a clogged filter. There is a filter between the carburetor and the fuel tank, which stops any dirt or debris from entering into the carburetor. This filter may get clogged with time and eliminates the fuel supply to the lawnmower. The filter must be cleaned, in this case, to continue the supply of fuel to the lawnmower
  • Closed valve: Some lawnmowers have a valve that stops the fuel supply to the carburetor. It is often turned off at the end of the season or when the lawnmower needs to be repaired. Make sure that this valve is not turned off
  • Clean the carburetor: Despite multiple efforts to halt the entrance of dirt into the carburetor, old gasoline can still form a film inside the carburetor, thus stopping its working. A malfunctioned carburetor will stop the supply of fuel to the lawnmower’s engine. You need to open the carburetor and clean it from inside using gasoline and a brush gently.

Final Remarks:

You don’t need to buy a new gas tank if it’s a little cracked, thanks to the methods mentioned above that can be used to resolve your problem. Gasoline leakage not only drains the fuel faster but can also be hazardous as it is highly flammable. So, it’s advised to get it fixed as soon as possible. Also, don’t forget to wear protective gloves to protect yourself from unnecessary burns and cuts. Safety goggles must also be used to protect your eyes from toxic fumes. All the tools used in the process must be kept out of children’s reach to avoid accidents.

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