I ran into a rough start/misfire issue last year and ended up replacing my fuel injectors. I started a thread when I was troubleshooting it because I could not find any complete instructions, write-ups, how-to's, etc. on how to replace the injectors in our DI engines. In the thread I mentioned that I would post a how-to in this forum, appreciate everyone who chimed in to help. I try to give back because I have saved countless time and money learning from a lot of you. This took longer to post than I wanted thanks to having my firstborn (poor guy gets blamed for a lot of stuff - mainly farts), but here's the how-to on replacing injectors! Below is a step by step guide on how to replace the fuel injectors on a 6.2L (L86) direct injection engine for the K2XX platform. If you have a different engine/platform you'll want to do your own research to ensure the replacement is done properly.
DISCLAIMER: I consider myself handy and have the right tools to do a lot of jobs on my vehicles - but I am not a certified technician. I spend a LOT of time researching and asking questions before I do any repairs. This is the result of online research, talking to people in this forum, and talking to technicians that I personally know. I also grew up fixing cars with my family - who are engineers with GM. If you do not have confidence in replacing fuel lines and/or opening up the intake portion of your engine then you should let a professional do this work.
You will need the following tools:
- Torque wrench for both ft/lb and in/lb specs.
- Socket set with extensions and a swivel adapter if you have one. There are some tight spots that you have to get to for bolts and a swivel adapter made it much easier.
- Trim removal kit, not critical but makes it much easier. This really helped with a set of push on clips for a wiring harness that's behind the intake manifold.
- MAF and throttle body cleaner if you want to clean your intake while it's apart, not critical though.
- Blue loctite for high pressure fuel pipe fittings.
- C-shaped fuel line removal tool, not required but greatly helps in quick removal of low pressure fuel pipe (can borrow a kit from an auto parts store).
You will need the following parts (again this is for the 6.2L L86 engine - yours could be different if you have a different engine/platform). GM says you must replace the fuel pipes after removing them, they may leak fuel if reinstalling old fuel pipes:
- Fuels injectors part # 12668393
- Intermediate #1 Fuel Pipe (crossrail that connects both fuel rails) part # 12677002
- Intermediate #2 Fuel Pipe (from crossrail fuel pipe to high pressure fuel pump) part # 12677004
- Fuel feed pipe w/check valve (from high pressure fuel pump to low pressure fuel line) part # 12618338
Steps to replace fuel injectors (pics/diagrams attached to provide visual aid). Carefully remove everything in these steps as they are tied to the intake of your engine - don't rush it. Clean off top of engine before starting removal as debris can seriously damage your engine if it falls into the intake:
1. With truck off, pull fuel pump fuse from main fuse box in engine bay (fuse #21).
2. Start the truck and let it run until it stalls out (can happen within a few seconds or take as much as 30 seconds). This ensures fuel is run out of the fuel lines and the fuel pumps/lines have no pressure. If you do not do this step the high pressure lines you will be removing can spray fuel everywhere and cause damage/injury.
3. After truck stalls out, shut it off and unhook the battery so the truck has no power.
4. Remove resonator box/intake tube going into throttle body. 2 clamps are loosened - 1 at the throttle bottle and 1 at air box. Disconnect MAF sensor electrical connection on intake tube by air box. Disconnect both driver and passenger clean-side fittings (removed by pressing on the light gray plastic strip and squeezing it together and pulling the fitting off the barb). Resonator box is now free to pull out of engine bay. Lots of videos on Youtube show how to do this is you're still unsure.
5. Disconnect PCV hose fitting next to throttle body (same style fitting as clean-side fittings on resonator box).
6. Remove throttle body (1 electrical connection and 4 bolts).
7. Unclip electrical wiring harnesses that run along both sides of the intake manifold (3 plastic push clips on each side). Trim removal tool can be helpful here, but mine pulled out fairly easily by hand.
8. Remove 5 intake manifold bolts on each side (10 total). They are finicky to get completely out as they have a little catch ring on them to not easily fall out of the intake manifold. If you can't wiggle it completely out, just make sure it's not fastened to the engine block any more and leave them in the manifold - you can still remove the manifold with them loosely in it.
9. This part was a pain - but slightly lift up intake manifold and pull toward you as much as you can. This will give you *some* room, not much, to reach behind the intake manifold and pull out 4 more of the push style clips holding the electrical wiring harness to the back of the intake manifold. It's tight because the manifold is right up against the firewall. I used a trim removal tool to get leverage on the clips and pull them out. It'll be a pain to remove some of them, don't be afraid to give it some muscle. (See pic below showing where clips are located)
10. With the bolts and clips all removed you can now lift the manifold off the top of the engine. Remove the black foam pad under the manifold to expose the fuel lines/rails. Be careful and try not to drop debris in the intake openings.
11. Tape off or put clean rags in your intake openings to prevent anything from falling in while you remove the fuel lines, rails, and injectors.
12. Unplug the electrical connections to the fuel rails (on the ends by the firewall).
13. Remove the 3 fuel lines from the high pressure fuel pump and 2 fuel rails (see pic below for fuel line/rail set up on the 6.2L L86). The 2 high pressure fuel pipes should have loctite on them, but they break loose fairly easily. I borrowed a fuel line removal kit from Autozone for the low pressure fuel line, it clicks into barb fittings. The low pressure fuel line (rests just above the driver side fuel rail and clips into the high pressure fuel pump) has a special fitting on each side of the pipe that is a pain to release without a special tool. The tool itself is a plastic 'c' shaped clip that goes around the fuel line and pushes into the pipe end, releasing it.
14. Slowly pull out each fuel rail, I had to firmly wiggle them but they came out by hand.
15. Look in each injector port and make sure there's no debris/crap in there. If you see anything try using a vacuum hose to suck it out or use something to swab out any debris. You want the injector ports clean so the teflon gaskets on the injectors seat properly in the port.
16. Swap your old injectors with the new injectors on the fuel rails. There's a metal clip on each injector holding it against the rail that can be a pain to take off and put back on, but you need them so don't damage them. I used a flathead screwdriver to pry them off, they clipped back on easily.
17. Reverse these steps to put it all back together. Make sure you torque all bolts and pipe fittings to spec or else you risk damage and/or leaks. Below is a pic of the torque specs, I highlighted the ones you need.
18. Start truck up and pray you did everything correctly.
19. If you drink, crack open a cold beer and take pride in your work and saving big bucks. If you don't drink, crack open a cold apple juice and take pride in your work and saving big bucks.