Upgrading Jeep's Engine: Carbartor To Fuel Injection

If you're looking to upgrade your Jeep's engine, converting from a carburetor to fuel injection is a great way to improve fuel efficiency and engine performance. This process involves replacing the carburetor with a fuel injection system, which can be done using fuel injection conversion kits that are widely available in the market. The most common system types are Throttle-Body Injection (TBI) and Multi-Port Injection (MPI). TBI systems are generally easier to install and more cost-effective, while MPI systems offer better fuel distribution and engine performance. It's important to note that this conversion process requires some technical expertise and know-how, and it's recommended to consult a professional or seek guidance from resources specific to your Jeep model.

Characteristics of Changing a 6-Cylinder Jeep Motor from Carburetor to Fuel Injection

Remove the carburetor

To remove the carburettor from your Jeep, you will need a Phillips head screwdriver, a wrench or socket set, and a rag. It is also recommended to wear protective equipment and work in a well-ventilated area.

First, turn off the fuel valve and disconnect the fuel line and the overflow hose from the carburettor. Remove any screws and clamps attaching the carburettor to the engine block, and pull it out. Use a rag to plug the hole left behind to prevent debris from falling in. Drain any remaining fuel from the carburettor.

Next, remove the float bowl and the float itself. There may be a gasket in the float bowl, so be careful not to tear it if you are planning on reusing it. With the float bowl removed, use a pair of needle-nose pliers to remove the hinge pin holding the float in place.

Now, take out the jets. There are two jets in the carburettor: the main jet and the needle jet. Remove them with a flathead screwdriver and hold them up to the light to check for clogs. If they are clogged, set them aside to be cleaned.

Finally, remove the mix and idle screws. For the mix screw, tighten it first and note how many turns it takes to be fully tightened, then unscrew it. Watch for a spring, O-ring, and washer that sometimes come with this screw. Now, remove the idle screw.

With all the components removed, it is time to clean the carburettor. Soak the parts in a chemical dip or spray carb cleaner through the various channels. Use a toothbrush or wire brush to remove grime from the exterior. Clean the jets with a wire made of a softer material than the jets themselves. Finally, use compressed air to remove any remaining debris and dry the components.

Install the injectors in the intake manifold

Upgrading your Jeep's engine from a carburetor to fuel injection can have numerous benefits, including improved starting, better reliability, and improved drivability in all types of weather and elevations.

Now, let's focus on the installation process of the injectors in the intake manifold. This process is a crucial step in converting your Jeep's engine from a carburetor to fuel injection. Here's a detailed guide on how to do it:

• Select the Appropriate Injectors: Choose injectors that match the specific requirements of your engine, such as the engine's output and desired power band characteristics. The selection of injectors will depend on the horsepower and the type of fuel your engine uses. For example, E85 fuel requires more fuel than pump gas to generate the same amount of power.
• Prepare the Intake Manifold: Remove the old intake manifold if you are replacing it. Clean the manifold and inspect it for any damage or carbon build-up. Ensure that the manifold is compatible with fuel injection and matches your engine's make and model.
• Mount the Fuel Rails: Install the fuel rails onto the intake manifold. Cut, tap, and machine the fuel rails to ensure they are securely mounted and at the correct height. This step may require professional help or a conversion service, as precise measurements and welding are often involved.
• Place the Injector Bungs: Properly position and install the injector bungs inside the intake manifold runners. The bungs are crucial for the secure placement of the injectors. Ensure they are welded securely and blended smoothly with the manifold.
• Install the Injectors: With the fuel rails and bungs in place, carefully insert the injectors into the bungs. Ensure they are securely seated and aligned correctly. The injectors should be placed above the intake valve of each port for multi-port fuel injection (MPFI) systems.
• Connect the Fuel Lines: Connect the fuel lines to the injectors and the fuel pump. Ensure that the fuel system, including the fuel filters and fuel pump, is compatible with fuel injection and can handle the higher fuel pressures required (typically between 40 to 60 psi for EFI systems).
• Test and Fine-Tune: Once the injectors are installed, test the system for any leaks and fine-tune the settings. Ensure that the ECU has the correct information and can make the necessary adjustments for optimal performance.

Remember, it is essential to have the correct tools and safety equipment when performing this upgrade. If you are unsure about any part of the process, it is always best to consult a professional mechanic or a specialist in fuel injection conversions.

Install the throttle body

To install the throttle body, you will need to follow these steps:

• Disconnect the negative battery lead.
• Remove the bolts attaching the mechanical fuel pump on the passenger side of the engine using a 1/2" wrench. Clean off any gasket material left behind and seal the hole using the block-off plate and a new gasket (provided in the kit). Reuse the old fuel pump bolts to secure the block-off plate.
• Remove the air cleaner, vacuum lines, and electrical connectors attached to the old carburetor. Only the PCV/Canister and Thermal vacuum switch and distributor advance vacuum line connections will need to be reconnected.
• Plug the Carb Bowl connection port on the charcoal canister.
• Disconnect the throttle return spring, throttle linkage, and fuel line bracket from the engine block, as well as the air cleaner bracket and any other upstream/downstream diverter valves, check valves, or other emissions equipment.
• Remove the old carburetor using a 7/16" socket or wrench. Take two of the old carburetor mounting nuts and attach them (doubled up) onto one of the mounting studs. Remove the stud by turning the lower nut. Continue removing the remaining nuts in this manner.
• Clean up any gasket material left on the throttle intake using a gasket scraper or razor blade, being careful not to let any debris fall into the manifold. Cover the throttle intake with a rag to prevent contamination.
• If your Jeep has an air pump and an air injection manifold (or air tubes), loosen the serpentine belt and rotate the air pump out of the way to access the forward-most bolt. Remove the bolts attaching the air tubes to the exhaust manifold and cap off the holes using the old air tube bolts, ensuring the bolt heads are flush with the metal to prevent exhaust leaks. If your Jeep has an air tube coming from the catalytic converter, this will need to be cut and sealed off.
• Remove the O2 sensor from the exhaust manifold using a 7/8" wrench. If your Jeep does not have an O2 sensor, most kits will provide a threaded bung that can be welded onto the exhaust downpipe.
• Install the new O2 sensor that comes with the kit using a 7/8" wrench.
• Remove the old coolant temperature switch from the intake manifold (typically using a 1" socket) and install the new coolant temperature switch provided in the kit, applying coolant-safe RTV to the outside edge of the switch for a secure seal.
• Place the rectangular gasket on top of the throttle intake, then place the TBI adapter plate on top. Secure the adapter plate using the four 1/4" Allen bolts supplied in the kit in a crisscross pattern to ensure a proper seal.
• Place the larger triangular-shaped gasket on top of the adapter plate, aligning the three holes. Ensure all Allen bolts are covered. Some older kits had gaskets that did not fit properly, requiring the use of RTV to seal off the Allen bolt heads and prevent vacuum leaks.
• Attach the TBI unit onto the adapter plate using the provided bolts and spoke washers.
• Remove the ECM and all the wiring attached directly to it. Cut open the wiring harness and remove the electrical tape and wire ties. This will allow you to trace the wires needed for the next steps. Most of these wires will be discarded.
• Remove the coolant overflow bottle from the driver's side fender well to access the Duraspark ignition module. There are two plugs attached to this module; you want the one with four wires (black, green, purple, and orange). These wires connect to a three-wire plug from the old harness.
• Locate the plug with a purple, orange, and black wire attached to it on the distributor. Splice the purple and orange wires from the Duraspark ignition module to the corresponding purple and orange wires on the distributor. Ground the black wires on both ends.
• The remaining green wire on the Duraspark ignition module plug needs to be routed across the engine bay and connected to the coil's negative terminal.
• Discard any remaining wires.

Now that the throttle body is installed, you can proceed with the rest of the fuel injection conversion, ensuring that all necessary parts are sourced and properly connected.

Install the sensors

To install the sensors for your Jeep's new fuel injection system, you will need to follow these steps:

Firstly, you will need to purchase a fuel injection kit that includes sensors. Some popular options include:

• Edelbrock Pro-Flo 2 EFI System
• Holley Terminator EFI System
• MSD Atomic EFI System
• Quick Fuel EFI System

Once you have purchased your kit, follow the specific instructions provided by the manufacturer. Here are some general steps to guide you through the process:

• Remove the old carburetor and associated components, such as the air cleaner, fuel pump, and lines.
• Install the mounting plate for the new throttle body.
• Remove and replace sections of the fuel supply and return lines as instructed.
• Mount the new electric fuel pump and filter, and reconnect the lines to the new throttle body.
• Apply RTV sealant to the throttle body mounting plate and let it dry for a few hours.
• Install a new coolant temperature sensor.
• Disconnect and mark the wires from the old carburetor that will be reused.
• Remove portions of the dash and glove box to access the factory ECM and wiring harness.
• Remove the factory wiring harness and separate the wires that need to be kept and those that will be permanently removed.
• Feed the new wiring harness through the firewall and separate the plugs for the new ECM and other components.
• Mount the diagnostics port and the new ECM plug for easy access.
• Reassemble the dash and confirm that all gauges and components are functioning before fully closing the dash.
• Mount the fuse block and install the check engine light.
• Wrap up the wire loom and clean up any excess wire.

By following these steps and referring to the specific instructions for your chosen fuel injection kit, you should be able to successfully install the sensors and complete the conversion to fuel injection.

Adjust the distributor

Adjusting the distributor on a Jeep is a complex process that requires careful attention to detail. Here is a step-by-step guide on how to do it:

Step 1: Turn the motor to Top Dead Center (TDC) on cylinder #1

Locate the number one cylinder, usually at the front of the engine, and turn the motor until it is at the start of the firing stroke. You can confirm this by removing the spark plug, placing your finger in the spark plug hole, and bumping the engine until you feel compression pushing your finger out of the hole.

Step 2: Position the distributor rotor

With the engine at TDC on cylinder #1, take off the distributor cap and note the position of the rotor. Make a mark to indicate where the rotor is pointing. If you're installing a new distributor, ensure the rotor on the new one is aligned with this mark.

Step 3: Install the new distributor

Remove the old distributor by unplugging the electrical line and vacuum line, and unbolting the clamp that holds it in place. Pull the distributor straight up and out of the block, being careful not to drop anything into the oil pump slot. Install the new distributor by dropping it into the slot and aligning the rotor with the mark from Step 2. Put the distributor cap back on, ensuring it is positioned correctly with the wires coming out of the distributor body. Tighten the clamp bolt to secure the distributor in place.

Step 4: Adjust the timing

Start the engine and check the timing marks with a timing light. If the timing is way off, turn off the engine and adjust the distributor by turning it clockwise or counterclockwise in small increments until the engine starts. Once the engine starts, fine-tune the timing by turning the distributor gradually while the engine is running, aiming for an idle speed of around 700-800 rpm. Re-check the timing marks with the timing light, aiming for 8-9 degrees of advance.

Step 5: Finalize the installation

Turn off the engine and tighten the distributor clamp bolt to prevent it from rotating. Reconnect the vacuum line to the distributor and the electrical line. Take the Jeep for a test drive to ensure it runs smoothly and accelerates well.

It is important to note that adjusting the distributor can be a tricky process, and it may require some trial and error to get the timing just right. Always exercise caution when working on your vehicle, and refer to a mechanic or a Jeep forum if you have any questions or concerns.

Frequently asked questions