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7.3L Injector Swap/Glow Plug Change

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This article is a step by step process to changing out 7.3L Powerstroke injectors, it also has information on how to change your glow plugs.

This article needs to be as helpful and informative as possible for the shade tree mechanic, so to make that happen we installed these injectors in the driveway using basic hand tools, not much different than how a backyard mechanic will be doing it if you decide to tackle the job. These instructions apply to the 1999-2003 Super Duty 7.3L Powerstroke, but the principle is the same for the older body style 1994-97 Powerstrokes.

  • Before doing anything, disconnect both batteries, this will ensure that you don’t short out any connections while swapping the injectors. Our cables were 9mm nuts, but may be different depending on application.
  • Remove the high-pressure oil pump plastic cover atop the motor and set it aside. It is held on with two 13mm plastic cap nuts. It doesn’t really need to be removed but leaning on it will break it, so just get it out of the way.
  • Remove the intake tube that runs from the air box to the turbo or aftermarket intake if installed. Getting the intake duct out of there gives you access to the valve cover. The more of the intake you remove the more room you’ll have to work with when swapping the driver’s side injectors out. We chose to remove the entire intake. A screwdriver is all that’s needed to loosen the clamps that hold it.
  • Loosen and remove the intercooler boots that connect to the intake spyder and the intercooler. Both intercooler boost tubes need to be removed from the engine bay to gain access to the valve covers. The driver’s side will come out pretty easily, but the passenger side requires some finagling to get it up and out. Just take your time and remember how you routed it so you can get it back in the same way when it goes back together.
  • Now it’s time to remove the valve covers. Using your 3/8-inch drive ratchet, extensions, wobble and sockets, remove the bolts that hold the covers down. Some of these are a little tougher to get to, especially the lower back bolts on the passenger side. This is where the wobble adapter comes in handy. Make sure to take note which bolts have the studs on them that are used to hold brackets, etc. There were five on our application. One holds the dipstick, two support the heater hoses and two on the driver’s side hold a wiring harness bracket down. After all the bolts have been removed you can slowly separate the valve cover from the head. The passenger side valve cover is a little tougher to remove, but just take your time and it will come up out of there. We found it easier to maneuver it after we removed the oil fill tube.
  • Next, unplug all the wire connections under the valve cover; there is one connection to each glow plug and one at each injector. Then disconnect the harness on the valve cover gasket itself. You can now remove the gasket and set it aside. Take care with this gasket, as they aren’t cheap to replace.
  • Now it’s time to pull the factory injectors. Start with the No. 8 injector (this is the driver’s side rear injector). To remove the injector, use a 1/4-inch drive ratchet and deep socket and remove the bolt on the bottom side of the injector retainer. When this bolt is removed, the retainer ring can be slid towards the topside of the injector, which allows the ring to clear the top-mounting bolt, which won’t need to be removed. Using a pry bar, you can pop the injector up out of the head. Be very careful what you pry on though. Place the pry bar under the retainer ring and pry against a sturdy spot on the head. Keep some rags handy because this is where it gets messy. Once the injector is removed, take a break. This gives time for the oil and fuel in the head to drain into the cylinder. Next remove the No. 7 injector (the passenger side rear) and again allow time for the fuel and oil to drain into the cylinder. Once those two injectors have been removed and the heads have drained, you can now remove the remaining six injectors in any order. As you remove each injector, check to make sure that each has the copper washer on the end near the nozzle. If not, you will need to remove the copper washer from the head. This is essential to ensure that the new injectors seat properly; the old copper washers must not be left in the head.
  • Now with all eight injectors out and sitting on the bench you need to remove the oil spout on each injector and put them on the new injectors. The oil spout is held onto the retainer ring with a single Allen head bolt. Make sure you get the bolt good and tight when installing it on the new injector. When installing the injectors back into the motor, make sure the copper washer remains on the nozzle; that washer prevents the oil and fuel from leaking into the motor. Also, in some applications the No. 8 injector will have a different colored connection and will be stamped with “LL,†which stands for long lead. The long lead injector was used in the No. 8 position to help cure some of the engine cackle. So if your new injectors come with a LL-stamped injector, its best to put this back into the No. 8 cylinder. You can take a very small amount of grease and apply it to the side of the copper washer which mates to the injector. This will help hold the copper washer in place, ensuring it doesn’t fall off and get crushed or improperly seated when you lower the injector into its bore.
  • The injectors don’t need to go back in any specific order, we just started at the back and worked forward. Before installing the injector, oil up the body of the injector and the o-rings, this will help lube them for installation. Place the injector in the head and tap the injector with a rubber mallet until it’s seated completely. Be gentle while doing this, these injectors aren’t cheap, so you don’t want to use a lot of force. We found that most of our injectors could be pushed down and seated just using the palm of our hands. You can usually hear a difference in sound when tapping the injector when it becomes fully seated. Also make sure that the retainer ring clears the topside bolt that wasn’t removed. When the injector is fully seated the retainer should slide back under the topside bolt and the bottom bolt can be reinstalled. Repeat this step for each injector. Once you have every injector installed, take a straight edge and place it across the top of the four injectors in each head. This will tell you if each injector is seated properly. We used a framing square to check ours. This step is essential to ensure that the injectors are set and will not leak.
  • Now the glow plugs need to be removed so that the oil and fuel can be pumped up out of the cylinders. The glow plugs just thread into the head, so again using the 1/4-inch ratchet and deep socket you can pull these up out of the heads. Now place the valve cover on the heads and hold them down with two or three bolts. They don’t need to be tightened down; you’re just placing the valve covers on so when you pump the oil out of the cylinders it doesn’t spray everywhere. To pump the oil out you will need a big ratchet and a 15/16-inch socket. From beneath the truck you want to crank the motor over manually using the ratchet on the end of the crankshaft. Three to four full revolutions of the crankshaft should be enough to clear the majority of the oil from the motor. Next, reconnect the batteries and turn the motor over a few times using the ignition. It doesn’t take much, just two or three two-second blurps on the key. Now you can disconnect the batteries again and remove the valve covers.
  • Reinstall the glow plugs, taking care to ensure that the glow plug goes into the correct hole and not one of the valleys of the head. With the glow plugs in you can now put the valve cover gaskets back on and reconnect all the wiring connections. The glow plug wires just push into place, so make sure they snug down. Make the connection on the injector itself and make sure the wire keeper is placed over the connection to keep it connected firmly. Reconnect the valve cover connection as well. Now you can place the valve cover back on and reinstall the bolts. When putting the valve cover on, especially the passenger cover, take care as not to disconnect any of the injector wires. We suggest before installing the valve cover bolts that you tip the cover forward and check to make sure everything is still connected properly.
  • At this point the truck just needs to go back together. Reinstall the intercooler boost tubes, air intake system and reconnect the batteries. Now, to start the truck, a battery charger may be needed depending on the strength of your batteries. Crank the truck over in 20 to 25 second cranks. The heads need to be re-filled with fuel and oil so the truck will just crank for what seems like forever. Take care as to not overheat the starter and burn it up. Once the air is out of the heads the truck will finally crank over and start. Let the truck idle for a while, then go out and drive it. It will take some miles before it really starts running right. After about 10 to 20 miles the air should get worked out of the system and you’ll notice the truck will start cleaning up and running right.

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