How to Replace the Primer Bulb on a Toro Lawnmower


Is your Toro lawnmower engine not starting? Perhaps you should think about priming it using the primer bulb on the carburetor. But wait, what to do if the bulb seems punctured? In this case, a primer bulb replacement becomes imminent to start the engine. If you aren’t used to DIY repairs, then don’t worry; we will help you in this blog post as we describe a step-by-step methodology for primer bulb replacement on a Toro lawnmower.

How to replace the primer bulb on a Toro lawnmower? You can follow the steps below:

  • Step 1: Allow your engine to cool down before replacement.
  • Step 2: Locate the primer bulb on your lawnmower. Remove the retaining ring if it’s there.
  • Step 3: Using a flat head screwdriver, pull the clip holding the bulb to its attachment at the carburetor.
  • Step 4: Pull the old bulb out using a pair of nose pliers.
  • Step 5: Attach the new bulb on the clip and insert it into the primer bulb assembly.

Primer bulbs are typically used in small engines that lack an electrical starting system, such as a starter motor. Their job is to manually choke the engine by drawing the fuel from the tank and supplying it to the carburetor. Quite often, the primer bulb may wear out due to continued exposure to rough conditions resulting in the engine not receiving adequate gasoline. Sometimes, the bulb may get punctured, thus making it useless altogether. In such cases, bulb replacement is much needed.

To get an in-depth elaboration of the steps mentioned above, we recommend that you keep reading this article.

Replacing the Primer Bulb on a Toro Lawnmower, step-by-step:

Replacing the primer bulb on a Toro lawnmower is fairly straightforward and can be accomplished in a few minutes. However, there are some worth considering points that we have laid down for you.

Equipment needed:

You don’t need hefty equipment to perform this simple replacement. All you need is a couple of flathead screwdrivers, a pair of nose pliers, and a new primer bulb that needs to be installed in place of the old one. It will help if a 17mm socket is available to you.

● Step 1: Perform the initial steps:

Before replacing the Toro primer bulb, you need to make sure that the lawnmower engine is cold. If you have just started the replacement after a mowing session, allow your machine to cool down for 15-20 minutes as the hot engine might cause damage to your skin when touched.

It is also better to replace the Toro engine’s spark plug wire before you begin to remove the primer bulb. This step is done as a precautionary measure to prevent the engine from starting accidentally.

● Step 2: Locate the primer bulb:

The primer bulb is located right next to the carburetor. In some Toro models, it may be present underneath the carburetor. A primer bulb typically has red or black/brown color. Generally, most primer bulbs have red or black retaining rings. Some bulbs are without any retaining ring.

Inspect your primer bulb visually to see if it appears unimpaired or not. If you notice it being torn, then that might be why you cannot prime the engine, and thus the bulb needs to be replaced with a new one.

● Step 3: Remove the Toro primer bulb from the carburetor:

The removal of the primer bulb can be accomplished by following these two steps:

– Removal of retaining ring:

First, remove the retaining ring that secures the Toro primer bulb externally. The ring comes off easily with the hand. If it doesn’t, you need to use a flat head screwdriver to pluck it out.

– Removal of the clip:

A clip that acts as a bulb holder secures the bulb internally. After the retaining ring is removed, a couple of grooves might be visible to you from each side of the bulb. You need to insert a flathead screwdriver onto each side to bring out the clip that holds the bulb.

– Removal of the bulb:

The clip is secured with its teeth. Inserting the screwdriver frees the teeth from the groove, and as a result, the clip comes out with the bulb. If you are facing difficulty bringing the clip out, pull the bulb out at the same time using a pair of nose pliers. If the Toro primer bulb is faulty, you don’t need to be that careful with it will be replaced eventually. However, it would be best to be cautious for a working primer bulb that you don’t end up puncturing it with the nose pliers.

● Step 4: Attaching a new bulb:

The faulty primer bulb has now been removed. In this step, you need the attach the new bulb that you purchased from the retailer for your particular Toro model. If you don’t know about the device’s model, take the faulty bulb with you, and the retailer will provide you with a new identical one.

– Clean the bulb attachment:

The bulb attachment point might have debris deposits formed. These deposits might develop in the carburetor if not cleaned properly. To dislodge them, use a dry rag to clean the area thoroughly. If available, it is even better to use a carburetor cleaner liquid for cleaning the attachment.

– Attach the bulb onto the clip:

Fix the new primer bulb onto the clip with its correct placement such that the tabs face upwards, i.e., along the direction of the bulb.

– Reinstall the bulb on the carburetor:

Insert the bulb inside a 17mm socket to fit perfectly with the clip being outside the socket. Although this can be performed by hand, a socket makes the job more convenient. It ensures the bulb and clip are sealed properly, thus preventing any leakage issue.

Press the socket inside the attachment and note when the clip gives a clicking sound. This indicates that the bulb is installed correctly. Afterward, remove the socket from the bulb.

– Reattach the retaining ring:

If your device uses a retaining ring, fix it outside the bulb to secure it completely.

– Inspect the new bulb:

With the new bulb installed, press it gently and notice if fuel is drawn into the carburetor. You might hear a soft noise of the fuel flowing into the carburetor with the bulb pressed. Since the bulb is now operating perfectly, try pulling your Toro mower’s cord and see if it starts this time around.

Related Questions:

1. How do primers work?

There are two major types of primers. Those are; bulb and automatic primers. Both types serve the same function, i.e., to supply fresh gasoline to the carburetor from the tank. But their way of operating is a little different.

-Bulb primer:

Bulb primers have a small rubber bulb outside, the purpose of which is to drive the gasoline out of the tank into the carburetor bowl. This fuel is fed for combustion to the engine.

-Automatic primer:

This primer extracts fuel by producing a vacuum when the engine is switched on. When the engine is turned off, this primer holds the fuel in the carburetor. Every time the engine starts, the carburetor has the fuel needed to supply it for combustion.

Both primers draw fuel from the tank to hold the carburetor full. If there is no fuel in your carburetor, the primer can be defective.

2. Why does a primer stop working?

Here are the factors that might cause the primer to stop working.

-Punctured bulb:

This is a defect for bulb primers. The rubber bulb can be damaged or ripped by sharp objects such as iron nails or sharp stones. The torn bulb prevents the flow of fuel from the tank to the carburetor. The torn bulb prevents the flow of fuel from the tank to the carburetor.

-Clogged fuel filter:

The primers draw fuel after it has gone through the fuel filter. Often the filter is clogged due to fuel deposits usually arising from old gasoline. Due to these deposits, the fuel does not enter the primer and cannot fulfill its purpose.

-The Cold Primer:

When the primer has been left standing for a while, there is a chance that the fuel will no longer be left in it. In this case, no fuel is left to be pumped into the combustion engine. Resultantly, the engine might not start in this state.

3. Do all lawnmowers have a primer bulb?

Primer bulbs are typically present in small engines. Generally, walk-behind lawnmowers use small engines and have primer bulbs.

In such engines, carburetors aren’t as sophisticated as compared to those used in cars. As a result, such carburetors have a rubber or plastic primer bulb to draw the fuel from the tank to the carburetor. In the end, this fuel is fed to the combustion engine.

4. How do you start a lawnmower with a primer?

To start a lawnmower with a primer, you must first check the fuel tank and see whether more fuel needs to be added. Then, press the primer bulb at least three times to ensure that the fuel has reached the carburetor.

With that done, shift the throttle lever to the highest position. Now, start the engine by pulling the cord. If it doesn’t start a few times after pulling the cord repeatedly, then your primer is faulty.  

Final Remarks:

Reinstalling a Toro primer bulb isn’t a hectic job and can be performed with minimal effort and simple equipment. You may not need to take it to a professional. For Toro lawnmowers that do not have a starter motor, primer bulbs offer a very easy way of starting the engine by supplying it with a gasoline charge. It should be noted that such engines have a high probability of developing debris deposits that can affect their performance. As a result, their filters should be kept clean. The fuel quality should be monitored and maintained after regular intervals.

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