Replacing Mechanical Fuel Pump On 22R: Step-By-Step Guide

If you're experiencing fuel leaks or low pressure in your carbureted truck, you may need to replace the mechanical fuel pump. This is a simple diaphragm pump with a pair of one-way valves embedded in a plastic barrier. In this guide, we'll walk you through the process of replacing the mechanical fuel pump on a 22R engine, commonly found in older Toyota trucks and 4Runners. We'll cover the steps to take, the tools you'll need, and some common pitfalls to avoid, so you can get your vehicle running smoothly again.

The pump's inner workings

The 22R mechanical fuel pump is a diaphragm pump with a pair of one-way valves embedded in a plastic barrier, which face opposite directions. This plastic barrier has a gasket on it, which interfaces with the fuel inlet line. The fuel return line, in red, bleeds excess fuel back to the fuel tank.

The diaphragm is made of canvas and is coated in a layer of neoprene. When the pump fails, it is usually due to the deterioration of this coat, which causes fuel to leak through the canvas and out from the two holes at the base of the pump.

Under the diaphragm is a spring, which pushes the diaphragm up and presses the fuel out of the pump. The camshaft of the engine contracts the spring and creates a vacuum, which forces the fuel out of the pump and into the carburetor at a consistent rate and pressure.

The 22R mechanical fuel pump is a simple but effective design, which relies on the motion of the engine to function.

Removing the plastic barrier

To begin removing the plastic barrier, you will need to have already disconnected the fuel lines and undone the bolts holding the pump in place. With the fuel pump removed from the engine, inspect it closely to identify the plastic barrier. It is a critical component, separating the diaphragm and the chamber with three connections.

Using a suitable tool, carefully pry or unscrew the plastic barrier from the fuel pump housing. It may be sealed or attached in a specific way, so take note of how it is secured to ensure proper reassembly. Once removed, you will be able to see the chamber with the three connections. One of these connections is the fuel inlet line, which will have a gasket to prevent leaks.

Take note of the orientation of the plastic barrier and its gasket(s) during removal, as proper alignment is crucial when reassembling the pump. It is also important to clean any residual gasket material from the mating surfaces to ensure a good seal when installing the new gasket(s).

Overall, removing the plastic barrier is a delicate process that requires attention to detail. By carefully disassembling and inspecting the fuel pump, you will be able to successfully replace the mechanical fuel pump on your 22R engine.

Cleaning old gaskets

To clean old gaskets on a mechanical fuel pump, you will need to remove the pump first. This will involve disconnecting the battery and draining the fuel tank. You will also need to remove the fuel lines, hoses, or clamps connected to the pump.

Once the pump is removed, you can start cleaning the gasket. Use a clean, lint-free cloth and a fuel system cleaner to wipe down the gasket and remove any debris, dirt, or old gasket sealant. You can also use a soft-bristled brush or a toothbrush to gently scrub the gasket. Ensure that you clean both sides of the gasket.

If the gasket is particularly dirty or damaged, you may need to soak it in a cleaning solution such as carburetor cleaner or gasoline. Use a container that is fuel-safe for this step. After soaking, use a soft-bristled brush to gently scrub away any remaining dirt or debris. Rinse the gasket with clean water and allow it to air dry completely before reinstalling it.

It is important to inspect the gasket for any signs of damage, wear, or corrosion during the cleaning process. If the gasket is torn, corroded, or severely degraded, it should be replaced with a new one. Do not reuse old gaskets that are not in good condition, as this can compromise the seal and lead to fuel leaks.

Additionally, always refer to the vehicle owner's manual for specific instructions and safety precautions when working on the fuel system. Some gaskets may require a light coat of gasket sealant on both sides for proper adhesion.

Using sealant

When replacing the mechanical fuel pump on a 22R engine, using a sealant is not necessary but can be helpful. The fuel pump is a simple diaphragm pump with a pair of one-way valves embedded in a plastic barrier. The pump features a gasket that interfaces with a fuel inlet line.

• Clean off any remnants of the old gasket from the pump and the engine block. Ensure the surface is free of debris and residue.
• Choose an appropriate gasket sealant. Options include Indian Head hi-tack, aviation brush-on sealants, or a light coating of sealer used on other gaskets. Some prefer Gasgacinch, a gasket sealant that allows for easy disassembly without the need for excessive force.
• Apply a light coating of the chosen sealant to both sides of the new gasket. You can use your finger to spread it smoothly and thinly. This will help the gasket adhere to the pump and the engine block.
• Before installing the new gasket, you can use a small amount of grease on the end of the rod to hold it in place temporarily. This will give you time to position the pump correctly.
• Position the new gasket and pump, ensuring the gasket is securely in place.
• Tighten the bolts to secure the pump. Be careful not to over-tighten, as the head is made of aluminium and the bolts can be easily over-torqued, leading to potential issues with holding strength.

Using a sealant can provide a better seal and make the process of replacing the mechanical fuel pump on a 22R engine more manageable. However, it is essential to allow sufficient curing time for the sealant, if required, and to follow the specific instructions for the chosen sealant product.

Torque wrench to tighten bolts

To replace a mechanical fuel pump on a 22R engine, you'll need to remove the fuel lines, undo the bolts, and clean off any old gasket residue. When installing the new pump, it's important to use a torque wrench to tighten the bolts to the correct torque value. This is crucial because the cylinder head is made of aluminum, which can easily be stripped if the bolts are over-tightened. Over-tightening can also reduce the holding strength of the bolts.

When using a torque wrench to tighten bolts, it is important to follow the correct torque sequence and specifications. The 22RE engine, for example, requires a specific sequence to be followed when tightening the head bolts to ensure proper torque distribution and prevent warping or damage to the cylinder head. The correct torque sequence for the 22RE engine can be found in repair manuals or online forums.

To properly use a torque wrench, start by cleaning the cylinder head and block surfaces to ensure a smooth mating surface. Then, apply a thin layer of engine oil to the threads and washer face of each head bolt. Insert the torque wrench onto the bolt and turn it until the specified torque value is reached. It is important to use a torque wrench with the correct range and increment scale to ensure accuracy.

For the fuel pump bolt specifically, the torque value should not exceed 9 ft-lbs (foot-pounds) for the 2F engine. For the 3F engine, the torque value is specified as 13 ft-lbs. It's important to note that tightening the bolt to the correct torque value is critical to ensure the fuel pump functions properly and does not leak.

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