Changing Fuel Injectors In Lb7 Duramax: Step-By-Step Guide

Replacing the fuel injectors in an LB7 Duramax engine is a complex task that requires a medium level of wrench-turning skills. The process changes slightly from model year to model year, but the fundamentals remain the same. The first step is to disconnect the battery and drain the coolant. Next, remove the A/C condenser, water thermostat, coolant neck, and fuel injection control module (FICM). Then, remove the glow plug harness, fuel lines, and fuel injector keys. Now, you can remove the valve cover and harness, followed by the fuel return lines. Finally, you can remove and replace the fuel injectors, making sure to clean and prep the injector cups and install new o-rings, washers, and seals. Reassemble the engine in the reverse order, top up the coolant and engine oil, and you're good to go!

Parts and tools needed

The parts and tools required to change the fuel injectors in an LB7 Duramax engine vary slightly depending on the source. However, the following list provides a comprehensive overview of what you will need:

Parts:

• 8 LB7 fuel injectors (GM part number: 97729095)
• Install Kit:
• 8 banjo washer pairs for connecting return lines to each injector
• 2 banjo washers for connecting the return line on each side to the head
• 16 external injector o-rings
• 8 copper seat washers
• 2 tubes of "Permatex Ultra Grey" RTV silicone sealant
• New injector cups and o-rings (in case the old ones are damaged during removal)
• New banjo bolts for the fuel return lines
• New valve cover gaskets
• New fuel connector tubes (optional but recommended to prevent rust)
• New fuel feed and return hoses (optional)
• New thermostat and upper radiator hose (optional)

Tools:

• 5mm allen bit, wrench, and ball end bit
• 8mm allen bit or ball end bit
• Torque wrench
• Basic set of metric tools
• 19mm wrench, stubby, crows foot
• Pick set
• Pry bar set
• Floor jack
• Fuel line disconnect tool
• Vise grip
• Star wrench
• Rubber hammer
• Shop vacuum
• New injector nozzles (optional upgrade for improved fuel mileage and driveability)

Disconnecting the battery and draining the coolant

Disconnecting the Battery:

• Locate the battery on the passenger side of the engine.
• Identify the negative and positive terminals of the battery.
• Disconnect the negative terminal first, followed by the positive terminal. This order is important to prevent any short circuits.
• Set the battery aside in a safe place, making sure it doesn't touch any metal parts of the vehicle.

Draining the Coolant:

• Locate the drain valve or plug on the passenger side of the wheel well.
• Place a bucket or container underneath the drain valve to collect the coolant.
• Open the drain valve or remove the drain plug to allow the coolant to flow out.
• Allow the coolant to drain completely. You may need to tilt the vehicle forward or jack up the front end to ensure all the coolant drains out.
• Once drained, close the drain valve or replace the drain plug securely.

It is important to perform these steps in the correct order to ensure your safety and prevent any damage to the vehicle. With the battery disconnected and the coolant drained, you can now proceed with the next steps in changing the fuel injectors in your LB7 Duramax engine.

Removing the A/C condenser, water thermostat, coolant neck, and FICM

To remove the A/C condenser, you will need to use a 1/2 drive ratchet to remove the tensioner pulley nut on the passenger side of the engine. Then, remove the A/C condenser and fold it by placing it on top of the passenger side battery. There is no need to evacuate the A/C.

Next, remove the water thermostat and coolant neck. It is recommended to replace the thermostats at this point with OEM thermostats.

Now, you will need to remove the Fuel Injection Control Module (FICM) from the engine so you can work under the valve covers. To do this, simply slide the plastic tabs outwards.

The following steps are not directly related to removing the A/C condenser, water thermostat, coolant neck, and FICM, but they are the subsequent steps to changing the fuel injectors in an LB7 Duramax:

Remove the glow plug harness using an 8mm ratchet wrench. There will be four nuts on each side of the heads, so be patient as this part is tedious work.

Remove the fuel lines with a fuel line disconnect tool, which can be purchased at any automotive or hardware store for around $10-15.

Remove the fuel injector keys. This key was designed to ensure the fuel injector does not come loose from vibration. Remember to reinstall this key when putting the fuel lines back together.

Remove the fuel lines on the engine with a 3/4 or 19mm wrench. If the lines are difficult to remove, use penetrating fluid or WD-40. Spray the liquid and let it sit for a few minutes to loosen the lines.

The valve cover is glued together with silicone, so use a pry bar to push the valve cover up or hit it with a rubber hammer to loosen it.

Remove the harness of the fuel injectors. Be careful not to lose the four bolts of the harness at the bottom of the oil pan.

Remove the lower valve cover with a 5mm Allen wrench. Take your time with this removal and clean the outside of the valve cover with a shop vacuum to avoid getting dirt in the heads.

Remove the fuel return lines with a 5mm Allen wrench. When reinstalling, make sure to only use 10 lbs of torque. Do not reuse the old banjo bolts; buy new ones.

Remove the fuel return banjo and fuel line. The fuel line will have a 12mm bolt on each side of the head. Remove these bolts and be careful not to lose the banjo washers. Do not reuse them; buy new ones for reinstallation.

Finally, you've reached the fuel injector. The fuel injector will have an injector hold-down, which you will need to remove using an 8mm Allen wrench. When reinstalling the fuel injector, torque to 45 lbs.

Use a small pry bar and a little patience to pry open the injector hold-down where you removed the 8mm bolt. If you have any difficulty removing it, spray WD-40 into the injector hole or bore. This will soften the carbon buildup in the injector tip.

Removing the glow plug harness, fuel lines, and injector keys

To remove the glow plug harness, you will need to use a 8mm ratchet wrench. There are four nuts on each side of the heads. This part of the process is tedious work, so be patient.

Next, you will need to remove the fuel lines with a fuel line disconnect tool. You can purchase this tool at any automotive or hardware store for around $10-15.

Finally, remove the fuel lines on the engine with a 3/4 or 19mm wrench. If you find the lines difficult to remove, use penetrating fluid or WD-40. Spray on the liquid and let it sit for a few minutes to loosen up the lines.

Now, remove the injector keys. This key was designed to ensure the fuel injector does not come loose from vibration. Remember to reinstall this key when you are putting the fuel lines back together.

The valve cover is glued together with silicone. To remove it, use a pry bar to push the valve cover up or hit it with a rubber hammer to loosen it.

Removing the valve cover and fuel return lines

To remove the valve cover and fuel return lines, you will need to start by removing the passenger-side wheel and inner fender (plastic part). Next, drain the coolant from the radiator by removing the drain plug on the bottom passenger side—this is necessary to prevent the combustion chamber from filling with coolant in case an injector cup comes out during this step. While the coolant is draining, disconnect the battery to prevent any damage to your ECM of modules.

Now, remove the A/C condenser and fold it on top of the passenger-side battery—there is no need to evacuate the A/C. Then, remove the water thermostat and coolant neck, replacing the thermostats at this point with OEM thermostats.

The next step is to remove the Fuel Injection Control Module (FICM) from the engine by sliding the plastic tabs outwards. This will give you more room to work under the valve covers. With the FICM removed, you should remove the Glow Plug Harness using an 8mm Ratchet Wrench—there will be four nuts on each side of the heads, so be patient as this part is tedious work.

Now, remove the fuel lines with a fuel line disconnect tool. You can purchase this tool at any automotive or hardware store for around $10-$15.

The valve cover is glued together with silicone, so use a pry bar to push the valve cover up or hit it with a rubber hammer to loosen it. Be careful not to lose the four bolts of the harness at the bottom of the oil pan.

With the lower valve cover removed, you will need to remove the fuel return line using a 5mm Allen Wrench. When reinstalling this item, make sure you only use 10 lb of torque. Also, do not use the old banjo bolts—buy new ones.

The fuel line will have a 12 mm bolt on each side of the head. Remove these bolts and be careful not to lose the banjo washer when you find it—but don't reuse it, buy a new one for the reinstallation.

You've now reached the fuel injector. The fuel injector will have an Injector Hold Down, and you will need to use an 8 mm Allen Wrench to remove the bolt. When reinstalling the fuel injector, torque to 45 lbs.

Use a small pry bar and a little patience to pry open the Injector Hold Down where you removed the 8 mm bolt. If you have any difficulty removing it, spray WD-40 into the injector hole or bore—this will soften the carbon buildup in the injector tip.

Frequently asked questions