Fuel Injector Conversion: Upgrading A 1984 F350 For Better Performance

Changing the fuel injectors on a 1984 F350 can be done at home and may improve engine performance if the injectors are worn or faulty. The process involves relieving fuel pressure, disconnecting the battery, removing the intake manifold, disconnecting electronics and vacuum lines, removing the fuel rail, and replacing the fuel injectors. New O-rings and a throttle body gasket are recommended for reinstallation. The cost of replacement injectors varies depending on quality, with some complete sets of new injectors costing around $3000.

Depressurise the fuel line

Depressurising the fuel line of your 1984 F350 is a necessary step before you can perform any fuel-related work on your truck. Here is a detailed, step-by-step guide on how to safely depressurise the fuel line:

Firstly, locate the fuel pump relay in the fuse box under the hood of your truck. With the engine running, carefully remove this relay. Your truck will continue to run, but it will begin to bog down as the fuel pressure decreases. At this point, you can turn off the engine. If you are uncomfortable with this method, an alternative approach is to simply remove the fuel cap, which will relieve any built-up pressure.

Another approach is to use a rag to wrap around the fuel line where it connects to the fuel rail. Then, carefully pop the line off the rail. Be cautious, as there will be a quick squirt of fuel. This method is commonly used when performing intake gasket and knock sensor work.

For a more precise method, locate the test port on the fuel rail. It resembles a valve stem on a tire and functions in a similar manner. By using the test port, you can safely depressurise the fuel system without having to worry about fuel spray or damage to the engine.

Always exercise caution when working with fuel systems, and ensure that you are wearing the appropriate personal protective equipment, including gloves and eye protection.

Disconnect the battery

Disconnecting the battery in your 1984 F350 is a simple process but an important one, especially when working on electrical components. Before beginning any work on your F350's electrical systems, such as the fuel injectors, it is crucial to disconnect the battery to prevent damage, perform maintenance, or replace it.

• Turn Off the Ignition: Always start by turning off your F350's ignition. Never attempt to disconnect the battery while the vehicle is powered on.
• Locate the Negative Terminal: Pop the hood of your F350 and locate the car battery. It is a large, block-like component with two large cables attached near the engine bay's surface. The negative terminal is marked with a "-" symbol and is usually black, while the positive terminal is marked with a "+" sign and is typically red.
• Remove Jewellery and Put on Safety Gear: To avoid any accidental connections, remove any jewellery, especially metal items, such as rings, necklaces, or watches. Put on safety gear, including gloves and safety goggles, to protect your skin and eyes during the process.
• Loosen the Nut on the Negative Terminal: Use a wrench to loosen the nut on the negative terminal by turning it counterclockwise. You may need to try different socket sizes to find the right fit. Remove any plastic caps on the terminals before proceeding.
• Disconnect the Negative Connector: After loosening the nut, remove the negative connector cable from the battery and ensure it is pushed aside and does not come into contact with the battery. Some modern vehicles may require a battery cable removal tool for this step.
• Disconnect the Positive Terminal: Repeat the same process for the positive terminal. Again, ensure that the cable is pushed away and cannot come into contact with the battery.

At this point, your F350's battery should be completely disconnected. You can now safely perform maintenance or replace the battery if needed. Remember to reconnect the battery in the reverse order, connecting the positive terminal first and then the negative. Ensure that you tighten the battery hold-down bracket to secure the battery in place.

Remove the intake manifold service cover

To remove the intake manifold service cover on a 1984 F350, you will need to set aside a good amount of time and gather the necessary tools and materials. Here is a step-by-step guide to help you through the process:

Step 1: Prepare the Engine

Before you begin, it is recommended to clean the engine as much as possible. Use compressed air or a vacuum to blow off or remove as much dirt and debris as you can from the engine bay. This will help reduce the chances of debris falling into the engine during the removal process.

Step 2: Prepare the Coolant and Fuel System

Open the coolant tank and drain the coolant from the petcock at the bottom of the passenger side. It is also important to relieve the fuel pressure. You can do this by disconnecting the battery or relieving the pressure on the driver's side fuel rail near the middle injector.

Step 3: Gather Tools and Materials

Ensure you have the following: a small inspection mirror, a retractable magnet, anti-freeze, anti-seize lubricant, high-temperature silicone, rubber gloves, clean rags, a good flashlight, and various hand tools such as wrenches, screwdrivers, and socket sets of different sizes.

Step 4: Remove Accessories

Remove the following components: the carburettor, distributor, linkages, temperature sender, upper radiator hose, thermostat housing, and AC compressor if your F350 is equipped with air conditioning.

Step 5: Remove the Intake Manifold Bolts

Now, you can remove the bolts holding the intake manifold in place. Use a flat-head screwdriver and a gentle persuasion tool, such as a hammer, to gently tap along the manifold where it meets the cylinder head to break the seal.

Step 6: Lift Off the Intake Manifold

Use an engine hoist or ask a helper to carefully lift off the intake manifold. Be cautious not to hit the hood or radiator during this process.

Step 7: Protect the Engine

Place a clean towel or cardboard over the lifter valley to catch any debris and protect the engine. You can also stuff paper towels or rags into the head ports to minimise the entry of debris.

Step 8: Remove Old Gaskets

Scrape off the old gaskets from the intake manifold and cylinder head. Be sure to invest in a gasket scraper for this step. You can also use a soft Roloc disc for more effective gasket removal.

Step 9: Clean the Mating Surfaces

Lightly sand the mating surfaces of the intake manifold and cylinder head with 320-grit wet-dry sandpaper. Then, wipe the surfaces with acetone to ensure they are free of oil and residue.

Step 10: Apply New Gaskets

Apply a high-quality sealant, such as RTV or Right Stuff, to the mating surfaces. Ensure you follow the manufacturer's instructions for proper application.

Step 11: Reinstall the Intake Manifold

Carefully position the intake manifold back into place, ensuring it is properly aligned. Start tightening the bolts in a cross pattern, working from the centre outwards. Snug the bolts first, then wait a few minutes before coming back to torque them to the specified torque sequence and values.

Step 12: Reassemble and Refill Coolant

Reinstall all the components you removed in Step 4. Once everything is back in place, refill the coolant and check for any leaks. If no leaks are found, let the engine reach operating temperature, then shut it off and retorque the bolts.

This process may take a full day or more, depending on your experience and the condition of the engine. Always refer to a service manual or seek advice from a qualified mechanic if you are unsure about any steps or procedures.

Disconnect the fuel supply and return lines from the fuel rail

Disconnecting the fuel supply and return lines from the fuel rail can be a tricky task, but with the right tools and techniques, it can be accomplished successfully. Here are some detailed instructions to guide you through the process:

Firstly, it is important to relieve the fuel pressure in your 1984 F350. This is a crucial safety step before beginning any work on the fuel system. Once the pressure is relieved, locate the hard lines that run from the end of the fuel rail and join the lines that run under the vehicle. These hard lines are connected to the fuel rail through quick-disconnect fittings.

To disconnect the fuel lines, you will need a suitable tool. There are various tools available for this purpose, such as plastic quick-disconnect kits, metal scissor-type tools, and circular coupling disconnect tools. Choose a tool that fits securely around both sides of the line. It may be necessary to tap the tool gently with a ratchet to ensure it is firmly in place.

Once the tool is in position, push the hard line into the quick-disconnect fitting. You may need to apply some force to free things up. While holding the tool firmly, pull the hard line out of the fitting. Be careful not to let the line fly off, as it may be under some pressure.

For the plastic collars on the fuel lines, you can use a pair of needle-nose pliers or a flat blade to release them. Simply push the plastic collar into the line while simultaneously pulling out the hard line. Make sure to securely fasten the clips back in their original locations.

It is worth noting that there are also specialised pliers designed specifically for disconnecting fuel line connectors. These can be useful if you are having difficulty with the other methods. Additionally, some fuel lines may have small spring-loaded clips holding the lines in place. If you encounter these, you may need to use a pick or small screwdriver to carefully remove the clips before disconnecting the lines.

Remember to work in a well-ventilated area and take all necessary safety precautions when working with fuel lines. Always refer to your vehicle's repair manual for specific instructions pertaining to your 1984 F350.

Remove the fuel rail mounting bolts

To remove the fuel rail mounting bolts, you will need a few simple tools, including an 8mm 6-point 1/4” drive socket, a 1/4” nut driver, a 3/8” 6” extension, a 3/8” universal joint, and a 3/8” to 1/4” adapter.

Before you begin, it is important to depressurise your fuel system, disconnect your battery, cover your fenders, and remove the engine bay cross braces and intake manifold brace, as these will be in the way.

Now, follow these steps:

• Disconnect the electrical connection to the engine temperature sensor near the thermostat housing. Squeeze the connector and pull it out.
• Disconnect the vacuum line from the front fuel rail pressure sensor. This will be the next sensor as you move rearward from the temperature sensor. Simply wiggle it off.
• Disconnect the electrical connection from the front fuel rail pressure sensor. Squeeze and pull off the electrical connection at the top of the sensor.
• Disconnect the electrical connection from the fuel rail temperature sensor. Moving rearward, you'll find this sensor next. Squeeze the connector and pull it off.
• Disconnect the vacuum line and electrical connection from the rear fuel rail pressure sensor. This sensor is partly under the cowl and a little harder to reach. Wiggle off the vacuum line and squeeze and pull off the electrical connector.
• Disconnect the electrical connectors from the fuel injectors. Carefully squeeze and pull up on the twelve (12) electrical connectors. The last 2 or 3 connections are under the cowl and may be more difficult to reach.
• Identify the fuel rail mounting bolts. There are two fuel rails, left and right, each held in place by three 8mm bolts. The left-hand rail provides fuel for the right-hand bank of fuel injectors and vice versa.
• Start removing the bolts. Using your 8mm socket, begin by loosening and removing the front-most bolt on the right-hand side (this will be for the left-hand fuel rail). As you loosen it, you may hear a hiss and smell fuel. Be sure to have a fire extinguisher handy.
• Remove the remaining bolts on the right-hand side. Work your way back, removing the second and third bolts. You may need the 3/8” ratchet, extension, and universal joint to access the third bolt under the cowl. Take your time and be careful as you remove the bolt.
• Remove the bolts on the left-hand rail. Repeat the process, removing the three bolts on the right side of the left-hand rail.

With all six bolts removed, the fuel rails should now be free to lift off the injectors. Remember to exercise caution, as there may still be residual fuel in the lines.

Frequently asked questions