Replacing Fuel Injectors In Your F350: A Step-By-Step Guide

Fuel injectors are an essential component of any vehicle, including the Ford F350. They regulate the amount of pressurised fuel used for each engine cycle, and there is one injector per cylinder. When a fuel injector fails or clogs, it can cause engine power to reduce and misfires to occur. The check engine light will turn on, and the engine may stall immediately after starting or fail to start altogether. To replace a fuel injector, you will need to remove the intake manifold to access the injectors. This can be a large job that may involve draining the coolant and oil and removing many engine components. However, some cars have plastic intake manifolds that do not have oil or coolant passages, making this process easier. Once you have accessed the fuel injector, it can be disconnected from the fuel rail and electrical connector and replaced with a new one.

Diagnosing fuel injector issues

Symptoms of Bad Fuel Injectors

Fuel injectors play a crucial role in regulating the amount of pressurized fuel used for each engine cycle. When they malfunction, it can lead to various issues. Some common symptoms of bad fuel injectors include:

• Rough idle: The engine operates unevenly due to an inconsistent fuel flow.
• Poor fuel economy: The air/fuel ratio and timing adjustments made by the PCM (powertrain control module) are affected, resulting in decreased fuel mileage.
• Misfires and loss of power: Incorrect air-fuel ratio causes engine misfires and a reduction in power and acceleration.
• Difficulty starting: Clogged or damaged injectors may not provide enough fuel to start the engine.
• Poor acceleration: The engine may experience sluggish performance due to insufficient fuel for combustion.
• Unusual exhaust smell: A damaged injector may release excess or unburned fuel through the exhaust, producing an unusual odor.

Causes of Bad Fuel Injectors

Understanding the causes of bad fuel injectors can help you take preventive measures:

• Clogged fuel injectors: Debris, dust, or contaminants in the fuel can accumulate in the injectors, restricting fuel flow and reducing engine power.
• Leaking fuel injector: When the injector doesn't close properly, excess fuel enters the combustion chamber, creating a strong fuel odor and wasting fuel.
• Electrical issues: Faulty wiring or damaged electrical components can cause the injector to send incorrect signals to the engine control module (ECM), leading to a poor fuel-to-air ratio.

Diagnosing Bad Fuel Injectors

To confidently diagnose bad fuel injectors, you can perform the following steps:

• Fuel pressure test: Connect a fuel pressure gauge to the rail to determine if the issue is related to the fuel injectors, fuel pump, or fuel filter. If the pressure is within the specified range, you can rule out the fuel pump and filter.
• Visual inspection: Look for signs of leakage or damage to the injectors. Unusual odors may also indicate leaking fuel.
• On-Board Diagnostics (OBD): Utilize your vehicle's OBD system to identify any misfires or error codes related to the injectors. If the Check Engine light is on, use an OBD scanner to retrieve the codes and pinpoint the affected cylinder.

Addressing the Issue

Once you've diagnosed the issue, it's important to take appropriate action:

• Cleaning or replacement: If the injectors are found to be clogged or damaged during the inspection, they may need to be cleaned or replaced to resolve the issue.
• Fuel system maintenance: To prolong the life of the fuel injectors, follow the scheduled maintenance for cleaning the fuel delivery system and injectors.
• Seek professional help: Fuel injector replacement is typically not a DIY job due to the risk of fire and the complexity of the repair. It's recommended to leave it to a qualified technician.

Disconnecting the fuel injector

Firstly, it is important to identify which fuel injector needs to be replaced. This may involve a dealer visit or some other form of diagnostic testing. Once you have identified the faulty fuel injector, clear the valve cover by removing the CAC tube, wiring to the glow plug control module, and the ICP sensor.

The next step is to remove the valve cover. To do this, you will need to remove several bolts, some of which may be difficult to access due to the evaporator case. With the valve cover removed, you can now take out the standpipe. The standpipe may be short or long, and if it is long, you may need to separate it.

Now, gently pry up and remove the oil rail bolts, being careful to hold the oil rail over the cylinder head to allow the oil to drain back into the crankcase. With the oil rail removed, you can access the fuel injector. Place a 19mm socket over the injector connector and press down firmly to disengage the lock tabs. This will allow you to pull the injector connector back into the head.

At this point, you can remove the injector hold-down clamp bolt. As you loosen this bolt, the injector and clamp will rise out of the injector bore. Check for any damaged o-rings and the copper combustion seal. The combustion seal is located at the bottom of the injector.

Now that the fuel injector is disconnected, you can proceed with installing the new injector. Remember to always use high-quality, OEM parts to ensure even power across the engine and a proper air-fuel mixture for all cylinders.

It is important to note that working with fuel can be dangerous, so always disconnect the battery and take proper precautions against fire when performing this procedure. Additionally, this is not a DIY job, and fuel injector replacement should be left to a professional to avoid the risk of fire and further damage to the vehicle.

Removing the intake manifold

To remove the intake manifold from your F350, you'll first need to disconnect the battery and relieve the fuel pressure. You'll also want to drain the coolant and remove the thermostat housing, upper radiator hose, distributor, carburettor, and AC compressor if your F350 is equipped with AC.

Next, you'll need to remove the intake bolts and use a screwdriver and hammer to gently break the seal between the manifold and the head. You may need to use a pry bar to finish breaking the seal. Once the seal is broken, you can lift the manifold off the engine. Be careful not to drop any debris into the engine while you're doing this.

Before refitting the new manifold, you'll need to clean the mating surfaces and apply a new gasket. Make sure to follow the torque specifications when reinstalling the bolts.

Finally, you can refill the coolant and start the engine to check for leaks.

This is a complex job that requires a good amount of knowledge and skill. If you're not comfortable doing it yourself, it's best to leave it to a professional.

Disconnecting the fuel rail and electrical connector

Step 1: Clear the Valve Cover

Remove the CAC tube and the wiring to the glow plug control module and ICP sensor. This will give you access to the valve cover. Remove the valve cover by unscrewing the bolts. Note that some of the bolts may be difficult to reach due to the evaporator case.

Step 2: Remove the Standpipe

The standpipe can be either short or long. If it is short, it should have separated easily when you removed the valve cover. If it is long, you will need to separate it manually. Gently pull the two halves apart. Once the oil rail is out, insert the lower part of the standpipe back into the branch tube.

Step 3: Remove the Oil Rail

Remove the bolts holding the oil rail in place and gently pry it up. Hold the oil rail over the cylinder head to allow the oil to drain back into the crankcase. This will prevent spillage and ensure that the oil can be reused.

Step 4: Disconnect the Injector Connector

Place a 19mm socket over the injector connector and press it down firmly. This will disengage the injector connector lock tabs, allowing you to pull the connector back into the head. You may need to apply some force, but be careful not to break the connector.

Step 5: Remove the Injector Clamp Bolt

The final step is to remove the bolt holding the injector clamp. As you loosen this bolt, the injector and clamp will rise out of the injector bore. With the injector now disconnected from the fuel rail and electrical connector, you can proceed to remove it and install the new one.

Remember to always take proper safety precautions when working with fuel and electrical systems. It is also important to have the necessary tools and knowledge before attempting this repair. If you are unsure or uncomfortable with any part of the process, it is best to consult a professional mechanic.

Reinstalling the new injector

To reinstall the new injector, you must first lubricate the new injector with clean oil and fit the old hold-down clamp onto it. Then, lubricate the injector connector O-ring with oil and press it into the hole in the head until it clicks. Ensure that the orientation of the new injector matches the other injector connectors.

Next, pour a small amount of oil onto the top of the new injector before installing the oil rail. Put everything back together, including the valve cover, and reconnect the wiring to the glow plug control module and ICP sensor.

Finally, reconnect the fuel injector to the fuel rail and electrical connector. Don't be surprised if the engine spins over for a while before firing up, as there is now a lot of air in the high-pressure system that needs to be compressed. The air will purge after some spirited driving.

It is important to note that replacing fuel injectors is not a DIY job and should be left to a professional. The risk of fire is high, and the repair can be complicated, requiring a good amount of knowledge to remove the injectors, intake manifold, fuel rail, and other components without causing further damage to the vehicle.

Frequently asked questions