Replacing The Bs 12 Hp Fuel Pump: Step-By-Step Guide

Replacing a fuel pump is a complex process that requires careful attention to detail and a good understanding of engines. Fuel pumps are used when the gas tank is mounted lower than the carburettor, and gravity cannot be relied on to carry gas through the fuel line. Briggs & Stratton pulse-type fuel pumps have either a plastic or metal body and develop pressure using the varying vacuum in the crankcase or off the intake manifold.

Before replacing a fuel pump, it is important to check whether it is functioning properly. This can be done by turning the key to the 'on' position and listening at the filler opening for a hum that indicates the pump is working. If the pump is not working, the next step is to check the fuse and relay. If these are functional, the pump itself may be faulty and will need to be replaced.

The process of replacing a fuel pump involves relieving the fuel system pressure, disconnecting the negative battery cable, draining the fuel tank, removing the pump from the tank, installing a new pump, and reconnecting the relevant cables and hoses. It is important to compare the new fuel pump with the original to ensure that the correct part has been obtained.

There are a variety of fuel pumps available on the market, including those designed for specific engines such as the Kohler CH11-CH16 and Briggs & Stratton engines.

How to Replace BS 12 HP Fuel Pump

Finding the fuel pump

The fuel pump is typically mounted in one of four places: between the tank and carburettor; below the carburettor; inside the fuel tank; or fitted into the fuel line between the tank and the fuel pump.

The fuel pump is a crucial component of a boat's fuel system, enabling fuel to travel from the tank through the rest of the system. However, finding it can be challenging as it may be located in different places depending on the boat's make and model. Here are some tips to help you locate the fuel pump in your boat:

• Refer to your boat's manual: The manual should have a detailed diagram or schematic showing the location of the fuel pump and other engine components. This can be a great starting point to familiarise yourself with the fuel system layout.
• Look for access panels or compartments: The fuel pump is often located in an easily accessible area to facilitate maintenance and repairs. Check for panels or compartments near the engine or fuel tank that may provide access to the fuel pump.
• Follow the fuel lines: The fuel pump is usually connected to the fuel lines, which run from the fuel tank to the engine. Trace these lines carefully, as they will lead you directly to the fuel pump.
• Consult a marine mechanic or boat forum: If you're still having trouble locating the fuel pump, don't hesitate to seek expert advice. Marine mechanics or boat forums can provide valuable insights and guidance on finding the fuel pump in your specific boat model.

Lawn mowers typically have fuel pumps mounted in one of four places:

• Between the tank and carburettor
• Below the carburettor
• Inside the fuel tank
• Fitted into the fuel line between the tank and the fuel pump

To check and fix a lawn mower fuel pump, follow these steps:

• Turn off the fuel valve at the base of the tank or use a fuel line clamp to stop the fuel flow.
• Loosen the mounting screws and remove the pump from the mounting bracket or carburettor.
• Inspect the pump for hairline cracks or other damage. If damaged, discard and replace the pump.

To fix a fuel pump in a Briggs & Stratton engine:

• With the fuel valve closed or the line clamped, remove the mounting screws.
• Disconnect the fuel hoses using needle-nose pliers.
• Inspect the pump body for cracks or damage, and soak metal parts in an all-purpose cleaner.
• Check the hoses for signs of wear and replace if necessary.
• Replace gaskets, diaphragms and springs with parts from a repair kit.

Locating the fuel pump is the first step towards effective maintenance and repairs. By following the tips and guidelines provided, you can confidently find the fuel pump in your boat or lawn mower and ensure its proper functioning. Remember to refer to your owner's manual and seek expert advice when needed to ensure a safe and efficient process.

Checking the fuel pump

Before replacing a fuel pump, it's important to check whether it is faulty. Here are some steps to help you determine if your fuel pump is malfunctioning and needs to be replaced.

Electrical Test

First, check the fuel pump fuse. Often, it's not the pump itself that's faulty, but rather the power supply to the pump. Refer to your owner's manual to locate the fuse box, then find the fuse corresponding to the fuel pump. Remove the fuse and inspect it for signs of failure. A blown fuse will appear broken or burned. If the fuse looks intact, check the remaining fuses related to the fuel system and replace any blown fuses if necessary.

Next, check the voltage at the pump itself. Even if the circuit appears to be supplying power, it's important to verify that the voltage is reaching the pump. Consult your vehicle's service manual to locate the correct testing point and follow the recommended procedure for checking the voltage.

Fuel Pressure Test

Another way to check the fuel pump is by performing a fuel pressure test. You can purchase or borrow a fuel pressure gauge from most auto parts stores or machine shops. Locate the fuel pump test point, usually near the fuel injectors, and attach the pressure gauge.

Have an assistant rev the engine while you observe the gauge. Check the pressure at idle speed and at the rated speed specified in your pump specifications. If the needle fails to move or moves below the specified pressure, it indicates that your fuel pump needs to be replaced.

Additional Checks

If your vehicle struggles to accelerate or exhibits signs of insufficient fuel supply, the issue could be related to a partially blocked or clogged fuel line, fuel filter, pump, or injector.

To check the fuel filter, remove it from the vehicle and drain any excess fuel. Use a short piece of rubber hose on the filter inlet and blow through it, paying attention to the resistance. If you encounter significant resistance or notice debris, the filter may need to be replaced.

If your vehicle fails to start, perform the following test: put the key in the ignition and turn it to the "ON" or "accessory" position without starting the engine. If you have fuel injection and an electric fuel pump, you should hear a clicking or buzzing sound indicating that the pump is operational.

If you don't hear the fuel pump turn on, there could be an issue with the fuel pump or insufficient fuel reaching the engine. You can use a fuel pressure gauge to test the fuel pressure and compare it to the recommended pressure specified in your vehicle's manual. If the measured pressure is lower than the recommended value, it suggests that your fuel pump may be malfunctioning.

Common Signs of a Faulty Fuel Pump

Some common symptoms of a malfunctioning fuel pump include:

• Difficulty starting the engine or a sputtering, stuttering start.
• The engine stalls during operation.
• The vehicle struggles to accelerate, especially at high speeds.

Replacement Options

If you determine that your fuel pump needs to be replaced, you have the option to install a rebuilt fuel pump, which is often more affordable than a new one. Some manufacturers also offer rebuild kits, allowing you to disassemble and rebuild the pump yourself following the provided instructions.

Alternatively, you can opt for a brand new fuel pump, ensuring that it is compatible with your specific engine model and vehicle type.

Safety Precautions

When working on or testing the fuel system, always prioritize safety. Keep a fire extinguisher nearby as a precaution.

Fixing the fuel pump

Step 1: Turn off the fuel valve

Locate the fuel valve at the base of the tank where the fuel line is attached and turn it off. If there is no fuel valve, use a fuel line clamp to stop the flow of gas.

Step 2: Remove the pump

Loosen the mounting screws and carefully take out the pump from its mounting bracket or carburetor. Check the external surfaces of the pump for any hairline cracks or other damage. If the pump is damaged, it should be discarded and replaced with a new one.

Step 3: Disconnect the fuel hoses

Using needle-nose pliers, disconnect the fuel hoses by loosening the clips. Remove the screws and either disassemble or replace the pump, depending on the extent of the damage.

Step 4: Inspect and clean the pump components

Examine the body of the pump for any cracks or other signs of damage. If there is damage, you may need to replace the entire pump. Soak metal parts in an all-purpose parts cleaner for up to 15 minutes.

Step 5: Check the hoses

Inspect the hoses for any cracks, softening, or hardening. Replace any worn or damaged parts to ensure a proper seal and smooth fuel flow.

Step 6: Replace old components

Discard and replace old gaskets, diaphragms, and springs with new ones from an original manufacturer's repair kit. This will help ensure a proper seal and optimal performance.

Step 7: Reassemble the pump

Place the diaphragm spring and the cup over the center of the pump chamber, and insert a valve spring. Install the diaphragm, gasket, and cover, securing them in place with pump screws. Tighten the screws using a torque wrench to ensure a firm hold.

Step 8: Reattach the pump

Attach the pump to its mounting bracket or carburetor using the pump mounting screws. Make sure it is securely fastened to prevent leaks and ensure optimal performance.

Step 9: Test the engine

After installing the new pump or completing the repairs, it is crucial to test the engine to verify that there are no leaks and that the fuel pump is functioning correctly. Run the engine and observe for any signs of fuel leakage or abnormal behavior.

Step 10: Consult a professional

If you encounter any difficulties during the process or are unsure about any steps, it is always best to consult a qualified mechanic or a Briggs and Stratton dealer for assistance. They can provide expert guidance and ensure that the job is done correctly and safely.

Removing the old fuel pump

To remove the old fuel pump, park your vehicle on a firm, level surface and engage the parking brake. Next, turn the key to the 'on' position and listen at the filler opening to check if the fuel pump is working properly. If no sound is made, it may be faulty and need replacing.

Now, locate the fuel pump fuse and relay. If the fuse is blown, replace it with a new one of the same amperage and re-check the fuel pump's operation. If the pump is still not working, there may be an issue with power or grounding.

Before proceeding, relieve the fuel system pressure by disconnecting the negative battery cable. Siphon or drain as much fuel as possible from the tank, and then disconnect the filler tube hose and electrical connection to the pump.

Support the fuel tank with a jack and a block of wood, and remove any retaining straps or bolts holding the tank in place. Carefully lower the tank and disconnect the fuel lines from the pump. Finally, remove the old fuel pump from the tank.

It is important to note that you should always refer to the manufacturer's instructions or a qualified mechanic for guidance on fuel pump replacement, as it can be a complex process.

Installing the new fuel pump

To install a new fuel pump, you will need to begin by relieving the fuel system pressure. Disconnect the negative battery cable and siphon or drain as much fuel as possible from the fuel tank. Disconnect the filler tube hose and the electrical connection to the pump.

Next, support the fuel tank with a jack and a block of wood. Remove any retaining straps or bolts holding the tank to the frame and carefully lower the tank.

Now you can disconnect the fuel lines and remove the old fuel pump from the tank. Compare the new fuel pump with the original to verify that you have the correct part, then install the new fuel pump.

Connect the fuel lines to the new pump. Lift the fuel tank up and install the retaining strap. Reconnect the filler tube hose and the electrical connector.

Finally, reconnect the negative battery cable. Fill the tank with gas and conduct a road test to confirm a successful repair.

Frequently asked questions