Replacing Fuel Injectors: 2003 Duramax Edition

Changing the fuel injectors on a 2003 Duramax is not an easy task and requires a lot of steps and specific tools. First, it is necessary to remove the passenger-side wheel and inside fender and drain the coolant from the radiator. Then, the tubing, intake, fuel filter bracket, and Fuel Injector Control Module (FICM) need to be removed. The connectors on the FICM need to be disconnected by sliding the tabs up and down. After that, the glow plug wire should be disconnected and moved out of the way. The next step is to remove the keepers on the high-pressure fuel lines and the injector lines using an 8mm socket and a 19mm wrench, respectively. The upper valve cover can then be removed using a pry bar and a socket as a fulcrum. To get to the lower valve cover, the injector wire harness must be disconnected and removed. A 5mm ball end Allen bit and extensions can help reach the bolts near the firewall. The injector return line can then be removed, being careful not to strip the bolts. All the injectors have a bracket holding them in place, which needs to be unscrewed with an 8mm Allen bit. Once the injector is loose, it can be popped out using a small pry bar. It is important to remove the copper washer from the bottom of the cup and ensure that the steel button under the bracket is not lost. If the injector comes out with the cup, the coolant will drain into the cylinder, so it is crucial to drain the coolant beforehand. The injector bore should be cleaned, and the cup should be reinstalled with new O-rings and red locktite. The mating surface in the head where the cup contacts should also be cleaned. The injector can then be reinstalled with a new copper washer and torqued down. The return lines, lower valve cover, injector harness, and upper valve cover can be reinstalled, ensuring proper torque and sequence. Finally, the injector lines and keepers can be installed, and the fuel filter and FICM can be put back in place. The driver's side process is similar, but with more components in the way, requiring additional steps for removal.

Drain coolant to prevent it from draining into the cylinders

To drain coolant to prevent it from draining into the cylinders when changing the fuel injectors on a 2003 Duramax, follow these steps:

First, prepare to remove the injector pump by draining the coolant. Here's how to do it:

• Locate the petcock in the radiator and open it to drain the coolant into an empty bucket.
• Once the draining is done, refill the radiator with distilled water and restart the vehicle.
• Allow the fluid to circulate and top it off as necessary.
• Repeat the drain process and refill until you see clear fluid coming out of the petcock.
• With the coolant capacity at hand, drain off half of the capacity and then refill with your choice of antifreeze.
• Allow the fluid to circulate and top off as necessary.
• Leaving the radiator cap off, raise the RPMs to burp off any air pockets.
• Test the antifreeze for proper temperature protection.

This process will help ensure that the coolant is drained and prevent it from draining into the cylinders when you remove the fuel injectors.

Remove the passenger-side wheel and inner fender

To remove the passenger-side wheel and inner fender, first, remove the passenger-side wheel. Then, remove the inner fender (black plastic). This will give you access to the coolant drain plug, which is located on the bottom passenger side. Removing the inner fender and draining the coolant are necessary in case an injector cup comes out with an injector, which would cause coolant to drain into the cylinder.

To remove the coolant drain plug, you will need to place a bucket underneath it, as the coolant will shoot straight towards the rear of the truck when you take the plug out.

Next, unhook the big blue turbo intake hose from the intercooler by loosening the 10mm nut on the clamp and pulling the hose off. Then, unhook the turbo intake hose from the top of the engine and wiggle it off.

Now you can start removing the tubing, intake, fuel filter bracket, and Fuel Injector Control Module (FICM) from the passenger side. The FICM has connectors with tabs that slide up and down to disconnect them. For the top one, pull up and towards the driver's side on the tab, and it will slide the connector out of the FICM. Pull down on the bottom connector, and it will come off the same way. After disconnecting the engine wire harness, you can remove the FF and FICM.

Disconnect the glow plug wire and move it out of the way. Some LB7s have a wire that goes to each individual glow plug, which will all need to be removed.

Remove the keepers on the high-pressure fuel lines with an 8mm socket or Phillips-head screwdriver. Then, remove the injector lines with a 19mm wrench.

Disconnect the fuel injector control module (FICM)

Disconnecting the Fuel Injector Control Module (FICM) is a crucial step in changing the fuel injectors on a 2003 Duramax. Here is a detailed guide on how to do it:

Step 1: Remove the Passenger-Side Wheel and Fender

Start by removing the passenger-side wheel and the inner fender (black plastic). This will give you better access to the engine and make the process easier.

Step 2: Drain the Coolant

Drain the coolant from the radiator by removing the drain plug on the bottom passenger side. This is important to do before proceeding, as it prevents coolant from spilling into the cylinders if an injector cup comes out with the injector.

Step 3: Disconnect Turbo Intake Hose

Locate the big blue turbo intake hose connected to the intercooler. Loosen the 10mm nut on the clamp and pull the hose off. Then, disconnect the turbo intake hose from the top of the engine and set it aside.

Step 4: Disconnect Fuel Lines and FICM

On the passenger side, remove all the tubing, intake, and the fuel filter bracket. There are typically three bolts holding the bracket, and a fourth one securing a coolant line.

Now, focus on the FICM. Its connectors have tabs that slide up and down for detachment. For the top connector, pull up and towards the driver's side on the tab to slide it out. The bottom connector is similar; pull down to disconnect.

Once the connectors are detached, you can pull the engine wire harness out of the way and then remove the FICM.

Step 5: Disconnect Glow Plug Wire

Disconnect the glow plug wire and move it out of the way. On some LB7 models, there may be a wire going to each individual glow plug, which will also need to be removed.

By following these steps, you will successfully disconnect the FICM, which is an essential step in changing the fuel injectors on your 2003 Duramax. Remember to refer to the detailed guides and seek professional advice if needed during the process.

Remove the upper and lower valve covers

To remove the upper and lower valve covers, you will need to first remove all the tubing, the intake, the FF bracket, and the FICM. Disconnect the connectors on the FICM by sliding the tabs up and down. After disconnecting the engine wire harness, you can pull it out of the way and start removing the FF and FICM.

Next, disconnect the glow plug wire and remove the metal bracket connecting them. Remove the keepers on the injector lines with an 8mm socket, and then remove the injector lines with a 19mm wrench.

To remove the upper valve cover, use the tabs sticking out as pry points. You can also remove the alternator and use its bracket as a fulcrum for more leverage against the valve cover.

For the lower valve cover, disconnect and remove the injector wire harness. It is held down to two injectors with four 7mm nuts and two 10mm gold bolts. After removing these, you can pull off the lower valve cover. Use a 5mm ball end allen bit and a variety of extensions to help when you get close to the firewall. Pulling the fender liner will make it easier to access the bolts at the back of the driver's side.

With the lower valve cover off, you can now remove the injector return line. Use a regular 5mm allen bit and tap it gently to avoid stripping the bolts.

Remove the injector lines and return lines

To remove the injector lines and return lines, first, remove the keepers on the injector lines with an 8mm socket. Then, remove the injector lines with a 19mm wrench.

Next, remove the upper valve cover. There are tabs sticking out of the upper valve cover that you can use as pry points. The factory sealant is very strong, so you may need to use a lot of force to remove it. You can try using a floor jack, or you can remove the alternator and use its bracket as a fulcrum for more leverage against the valve cover.

Now, you can remove the lower valve cover. First, disconnect and remove the injector wire harness. It is held down to two injectors with four 7mm nuts and two 10mm gold bolts. You only need to hold on to the 10mm bolts as the 7mm nuts are permanently fixed to the harness.

With the lower valve cover removed, you can now remove the injector return line. Be careful with these bolts as they strip easily. Try using a regular 5mm allen bit and tap it into place.

Finally, you can now remove the injectors. All the injectors have a bracket holding them in place, so unscrew them with an 8mm allen bit. Make sure not to strip them. To pop them out, first, give them a little twist to ensure they aren't stuck to the cup. Then, use a small pry bar to pop them out from the top, using the bottom of the high-pressure supply line on the injector as a pry point and the head bolt as your fulcrum. Make sure to remove the copper washer from the bottom of the cup if it doesn't come out with the injector.

Frequently asked questions