Cleaning injectors

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Cleaning Fuel Injectors On The BMW E30 3Series

Penguin Technical Article, written by Jared Fenton

Difficulty Level: 3

Difficulty scale: Adding air to your tires is level one

Rebuilding a BMW Motor is level ten


     Is your car running sluggishly? Are you noticing a slight stumble as you drive? Chances are, your fuel injectors need to be cleaned. In this tech article, I will go over the easy steps in removing the fuel injectors and cleaning them out. This article applies to my E30 325i 6 cylinder, however the principles behind this apply to nearly every car in general. Usually, most people just run a can of fuel injector cleaner in a full tank of gas. I would also recommend this, but in cases of cars that have been poorly maintained or have been sitting for a while, the only way to get those injectors truly clean is to pull them out.


     The first step is to disconnect the battery, as we will be working around fuel injection components and raw fuel. You don’t want a spike going through the system. This could fry your fuel injection computer. Also, you don’t want t a random spark igniting raw fuel. This is VERY bad. You will have to sit back and watch as your car goes up in flames. Disconnect the battery and be safe.

     Run the car until you have less than a quarter tank of fuel in there. This will reduce the overall amount of fuel pressure in the system and help prevent raw fuel from gushing out when you remove the injectors. Now, start out by removing the hose clamp holding the fuel line to the [[fuel pressure regulator and plug the fuel line using a bolt. Also disconnect the vacuum hose at the top of the regulator. Now look at the rear of the engine on the passenger side right above the valve cover. You will see the connection for the rear fuel line. Loosen the hose clamp that holds it to the [[fuel rail and remove the fuel line. Plug the end of the fuel line with a bolt. Be prepared for some raw fuel to spill out of the lines. Just have a rag nearby to clean the fuel up.

     Now, Remove the four 10mm bolts that hold the bracket between the valve cover and the intake manifold. Now take the bracket off and set it aside. We will need to remove this bracket in order to remove the fuel rail. Now loosen the hose clamp holding the breather hose to the valve cover and pull the breather hose off and move it out of the way.      We now must remove the six electrical connectors for the fuel injectors. Simply push the metal bar in and pull up on the connectors to remove them. Now, locate the four 10mm bolts that hold the fuel rail in place.

     Now, pull up on the fuel rail evenly from each end. You may have to use a little force to get the injectors out of the intake manifold. Once out, maneuver the whole fuel rail from out between the cylinder head and the intake manifold. Be sure to have a container or some other sort of tray around to catch the extra fuel inside the fuel rail. Now take the whole fuel rail over to a workbench or other suitable work area.

     We will now need to separate the fuel injectors from the fuel rail. Use a small flathead screwdriver to remove the retaining clips holding the injectors on and store them in a safe place. Now pull the injectors out of the fuel rails. You may have to use a little force to get them out. Keep in mind that you will most likely have a little bit of gas spill out when you remove them. Once out, remove the old seals on the top and bottom of the injectors and throw them away. You never want to re-use injector seals. If you do, there is a chance they may crack. This could cause an air leak or worse, cause raw fuel to leak out.

     With the injectors out, you might see a build-up of crud on the tips. This is usually a mixture of carbon deposits, fuel additives and gas. Use a rag to wipe off as much as you can. Now, get a can of brake cleaner and spray the outside of the injectors and the tips. Use a soft brush to remove any grime on the tips. Now spray a bit of brake cleaner down the inside of each injector and blow them out with some compressed air. You may be surprised at what comes out of there. Each fuel injector has a small filter that collects any debris or crud in the fuel system. Spraying the brake cleaner in there will dissolve any deposits in there.

     A good way to clean the inside is to spray cleaner in there, then hit it with compressed air. Keep doing this until the brake cleaner coming out is clear. This is an indication that they are clean. CAUTION: be sure to use goggles when you do this, as the compressed air will spray the cleaner everywhere. You don’t want this stuff to get into your eyes.

     Once you have all the injectors clean, get some new fuel injector seals and place them on each end of each injector. You will need 12 of them. Now to re-install them, put a little engine oil on the outside of the seals and press them back into the fuel rail. The engine oil will help you push them into the fuel rail as well as help seal them. Now re-install the retaining clips the secure the injectors into the fuel rail.

     Now, go back to the car and plug each injector port with a small piece of paper towel. Now take some brake cleaner and a small brush and clean the area around the injector ports. This will clean the area and prevent any loose dirt or debris from entering the injector ports. Take the paper towels out and look inside each port to make sure there is no dirt in there. If there is, use a small vacuum to suck it out.

     Coat each lower injector seal with a small bit of engine oil and position the fuel rail/ fuel injectors back in place in the intake manifold. Now, using equal pressure on both ends of the fuel rail, push down until each injector seats in the manifold. Now re-install the four 10mm bolts that hold the fuel rail in place.

     Once installed, re-attach the fuel line on the rear of the fuel rail and tighten the hose clamp that holds it in place. Now move to the front of the rail and re-attach the fuel line to the fuel pressure regulator and tighten the hose clamp that holds it in place. Also re-connect the vacuum hose at the top of the regulator. Now push the electrical connectors for the fuel injectors back on. Just push them down until they click.

     Now take the valve cover breather hose and push it back onto its fitting on the valve cover and tighten the hose clamp that holds it on. Next, re-attach the bracket that holds the intake manifold to the valve cover and install the four 10mm bolts that hold it in place. Now would be a good time to change the fuel filter on the car if you have not already done so. 

     Now re-connect the battery and fill the tank up. When you restart the car, it may take a few times to get it to run. This is normal. Keep in mind that the fuel system is under constant pressure and we just opened it up, introducing air into the fuel lines. It will take a little time for the fuel pump to deliver fuel to the injectors and pump all the air out of the system.

     Well, there you have it - it's really not too difficult at all.  If you would like to see more technical articles like this one, please continue to support Pelican Parts with all your parts needs.  If you like what you see here, then please visit our on-line BMW catalog and help support the collection and creating of new and informative technical articles like this one.  Your continued support directly affects the expansion and existence of this site and technical articles like this one.  As always, if you have any questions or comments about this helpful article, please drop us a line.