Regan Brown
Primer bulbs are used in small engines to help with the flow of fuel. They are generic parts that are used in a variety of power equipment. Primer bulbs work through a pair of one-way valves. When you push the bulb down, it pushes fuel from the carb body into the throat. When you release it, it sucks more fuel up to replace the fuel it pushed in. If the bulb is cracked or the two valves are not working properly, it won't work. In this case, you may need to replace the bulb or the entire carb.
| Characteristics | Values |
|---|---|
| Purpose | To pull fuel through the carburetor and return it to the tank to purge the air from the fuel line |
| Fuel flow | Fuel should move from the carburetor to the bulb, then flow back to the tank |
| Functionality | The bulb works through a pair of one-way valves; when pushed down, it pushes fuel from the carburetor into the throat, and when released, it sucks fuel up to replace the fuel pushed out |
| Troubleshooting | If the bulb is not filling with fuel, check for cracks or holes, ensure the fuel lines are not cracked and are long enough to reach the fuel in the tank, and check that the fuel filter is attached correctly |
| Compatibility | Inline primer bulbs are compatible with various equipment, including boats, cars, and leaf blowers |
| Price | Prices vary depending on the brand and specifications, ranging from $7.99 to $38.99 |
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What You'll Learn
Primer bulb not filling up
If your primer bulb is not filling up, there are several potential causes and solutions you can try.
Firstly, check the primer bulb for any cracks or holes. A cracked bulb will not function properly and will need to be replaced. Additionally, ensure that your fuel lines are not damaged or cracked and that they are long enough to reach the fuel in your tank.
If the bulb and fuel lines appear intact, the issue may lie with the check valve. The primer bulb operates through a pair of one-way valves. When you push the bulb down, it should push fuel from the carb body into the throat, and when you release it, it should suck more fuel up to replace what was pushed out. If the valves are not working correctly, the bulb will not fill.
Another potential cause could be that the fuel lines are reversed. Try the following: push the bulb down and hold your finger tight over the end of the line that goes back to the tank, then release the bulb. If you do this a few times and the bulb does not return to its original position, the lines may be reversed, causing a leak and preventing the bulb from filling.
If you are still experiencing issues, it may be helpful to consult a professional mechanic or seek advice from a specialist forum or community.
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Reversed fuel lines
Reversing the fuel lines on a purge bulb can cause issues with the functioning of the engine. For instance, if the fuel supply line is hooked up to the primer bulb, the engine may only run for a second or two. This is because the primer is only forcing a small amount of fuel through the carburettor, which is insufficient to sustain the engine.
In some cases, reversing the fuel lines can cause the engine to stall almost immediately after starting. This may be due to the fuel lines being connected to the wrong nipples on the fuel tank, which can result in gas overflowing from the top of the tank or exiting from the hose at the back of the engine cases.
Another potential issue with reversed fuel lines is that the engine may not start at all. This is because the fuel lines will be trying to pump fuel to a closed fuel pressure regulator, building up pressure without achieving ignition.
To avoid these issues, it is important to ensure that the fuel lines are connected correctly. The fuel line from the carburettor should go into the purge bulb, and the other fitting on the purge bulb should connect to the line that returns to the fuel tank. Additionally, the blow side of the bulb goes back into the tank, while the suction side is usually a short line that connects directly to the carburettor.
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Cracked primer bulb
A cracked primer bulb can cause an air leak, which can lead to a loss of power and fuel leakage. If the crack is small, a temporary fix can be done using super glue and swingline rubber finger tips. However, it is recommended to replace the primer bulb as soon as possible, especially if the equipment is a saw, as the crack may cause an air leak after running for a while, leading to a loss of power.
The process of replacing a primer bulb varies depending on the equipment. For example, replacing the primer bulb on a Husky K760 chop saw requires significant mechanical disassembly, while primer bulbs on Stihl chain saws and other similar equipment are generally easier to access and replace.
There are also DIY repair options available for primer bulbs, which can be done cheaply and quickly. This typically involves removing the carb, disconnecting the fuel lines and throttle cable, and replacing the primer bulb housing. It is important to note that incorrect reassembly can cause the carb to malfunction.
Primer bulbs are available for purchase online and at various retailers, with prices ranging from a few dollars to around $40, depending on the specific product and its compatibility with certain equipment.
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Faulty check valves
A faulty check valve is one of the most common issues with inline primer bulbs. This can be caused by a variety of factors, including:
- Air leaks in the fuel line system: If there is an air leak, the primer bulb may draw air into the fuel system instead of fuel, resulting in a 'soft' feel. This can be due to loose or damaged fuel line connectors, o-rings, or hose clamps, as well as cracked or deteriorated fuel lines.
- Incorrect installation: The primer bulb must be installed in the correct direction, with the arrow pointing towards the engine, to ensure proper fuel flow.
- Blocked fuel tank vent: A blocked or closed fuel tank vent can create a vacuum in the fuel system, preventing the bulb from functioning properly.
- Manufacturing defects: In some cases, the issue may be due to a manufacturing defect, such as faulty plastic valves.
- Fuel pump issues: While less likely, it is possible that the fuel pump is not delivering enough fuel, causing air to be drawn into the system.
To troubleshoot a faulty check valve, it is recommended to inspect the fuel lines and connections for any signs of damage or deterioration, ensure proper installation, and check for any blockages in the fuel tank vent. If these issues are not the cause, it may be necessary to try a different primer bulb or consult a mechanic to diagnose potential problems with the fuel pump.
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Using ethanol fuel
Ethanol is a common additive in gasoline fuels, and it can cause issues with the primer bulb and other components in the fuel system. Ethanol tends to attack rubber, reducing its flexibility and causing it to become stiff and brittle over time. This can lead to cracking and leakage, especially if the rubber is older and not made from modern alcohol-resistant compounds.
When using ethanol fuel, it is essential to ensure that all rubber components, including the primer bulb, fuel hoses, and gaskets, are made from alcohol-resistant rubber. Older rubber parts should be replaced with ethanol-compatible ones to prevent damage and maintain the integrity of the fuel system.
The primer bulb plays a crucial role in the fuel line, and its proper functioning is essential for starting the engine. When the bulb is squeezed, it creates pressure that closes the inlet valve and opens the outlet valve, allowing fuel to flow toward the engine. Releasing the bulb creates suction, which closes the outlet valve and opens the inlet valve, drawing fuel from the tank into the bulb. This process is repeated until the fuel line is filled and primed, making it easier for the engine to start.
Some users have reported issues with primer bulbs not filling properly, which can be caused by cracked bulbs or faulty check valves. It is important to inspect the primer bulb for any signs of damage and ensure that the fuel lines are connected correctly. The inlet line should be attached to a weighted filter, allowing for maximum fuel contact, while the return line needs to be submerged in the fuel tank.
When using ethanol fuel, it is recommended to regularly inspect and maintain the primer bulb and other fuel system components. Replacing the rubber diaphragms inside the carburetor at regular intervals can help prevent issues caused by ethanol's damaging effects. Keeping spare parts, such as primer bulbs and fuel lines, is also advisable to facilitate quick repairs and minimize downtime.
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Frequently asked questions
A:
The inline primer bulb on a hand fuel line works by pulling fuel through the carburettor (carb) and returning it to the tank to purge the air from the fuel line.
A:
An inline primer bulb is used to remove air from the fuel line, allowing the engine to run smoothly.
A:
You can check if your inline primer bulb is working by pressing it. If it is working, you should feel it blow out on one side and suction on the other. The blow side returns fuel to the tank, and the suction side is usually a short line that goes directly to the carb.
A:
Connecting the fuel lines incorrectly can damage the diaphragm in the carb and cause the engine to stall.
A:
If your inline primer bulb is not filling with fuel, check for cracks or holes in the bulb and ensure that the fuel lines are not cracked or leaking. Also, make sure the lines are snug and long enough to reach the fuel in the tank.
