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Pelican Technical Article:

Cleaning Fuel Injectors On The BMW E30 3Series
Jared Fenton
Wayne R. Dempsey

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 325is 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.

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     That said, let’s begin. 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. This picture shows the fuel pressure 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. This picture shows the location near the front of the engine. This picture shows the bolts near the rear.

     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 coffee can 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 (Pelican Parts carries these seals for $0.61 each. 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 it’s 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 out 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 online 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.

Comments and Suggestions:
salteedogComments: I was able to remove the fuel injectors of my '87 325 2.7L without too much issue. After bleeding fuel pressure, I disconnected the 6 injector electrical connectors by pushing the connector clips toward the connector body then pulled the connectors apart from the fuel injector. The fuel supply and return hoses from the fuel rail were disconnected. I unbolted the fuel rail from the intake manifold. There are two or three bolts there. I had a hard time unseating the injectors from the fuel rail and the intake manifold. So, I used a little leverage and was able to gentle pry the fuel rail with the injectors as a unit from the intake manifold. Once the fuel rail with the injectors was in hand, I removed the 6 retaining clips which secure each injector to the fuel rail. I replaced the rebuilt injectors with new o-rings and a little gear oil for coating the o-rings per the Bentley manual and installed everything in reverse order. It seems almost impossible to me to swap out an injector one at a time. All must come out with the fuel rail at the same least with this car.
December 7, 2012
 Followup from the Pelican Staff: Sometimes a tech may just want to lift the rail to remove one injector and change it's position to check the cause of a misfire. This is a pretty easy rail to remove. - Nick at Pelican Parts  
salteedogComments: This is for Kris, those type square u-pins of which you speak are not intended to be removed from the connector like your picture shows. If you push at the middle of it toward the connector body with your finger or a tool, it unlocks the connector and the connector can be pulled apart while retaining the u-pin as you call it. There are many connectors on the bmw that are of this design.
December 7, 2012
 Followup from the Pelican Staff: The older Bosch style connectors have a small thin wire securing the connector to the plug and those should be removed first. The later design has the middle of the wire exposed and you can push on it. It flexes the wire and releases the tabs so the connector can be removed. - Nick at Pelican Parts  
KrisComments: If you're struggling to lift the injectors all at once with the fuel rail likely, as suggested here, then unclip the injectors-it's easy-remove the fuel rail, and pull the injectors out individually. Some will come out easy, others will be amazingly stubborn. Use penetrant. Expect lacerated knuckles.

BTW, it may be best to remove the valve cover first for this job. I did.
October 1, 2012
 Followup from the Pelican Staff: Thanks for the advice and don't forget the lubricate the injector O rings because they can tear and leak if you force them out. It's a good idea to replace the O rings if you are removing the injectors. - Nick at Pelican Parts  
KrisComments: "Simply push the metal bar in and pull up on the connectors to remove them."

Wish it was always so. But it isn't. My '90 325iC did not have the push pin connector but square U-pins that are "impossible" to get out. Here is a photo of the pins and the tool I used to "fish" them out blindly. It will take a while but it is possible.
October 1, 2012
 Followup from the Pelican Staff: These use the older style Bosch connectors, the new one have a spring to release the tabs - Nick at Pelican Parts  
ratfink77Comments: Detailed diagrams of every BMW you can imagine are on If you can't find pictures, check it out.

If your injectors are stuck in the intake, spray some penetrating oil around the base of the injectors, then wiggle the whole rail and pull. Mine still wouldn't loosen, so I rigged a couple of pry bars with valve cover removed to pry up on the front end of the rail and it popped loose.
May 17, 2012
 Followup from the Pelican Staff: Thanks for the tips for our readers - Kerry at Pelican Parts  
Magoo 325iComments: Follow up, thanks to another great article by Wayne, I found an answer to my question. Its amazing what a little further research will do. Over half the comments on here make no sense or just complain.. do a little work yourself, or take it to a mechanic
May 14, 2012
 Followup from the Pelican Staff: We're here to help - Kerry at Pelican Parts  
Magoo 325IComments: I have a problem with my injectors.. I am blind, pictures wont help lol.. I have r and r'd my injectors and fuel reail many times for other reasons, like getting to water hoses to replace them. There is, however a kind of clip on the injector at the nozzle. It feels like it would perhaps hold the nozzle in place. Mine are rusted and 2 of them are broken off. Are these replaceable and if so, what the hell are they called and do you guys carry them?

Any Quick help would be appreciated... Keep up the amazing work guys, you are helping a blind dude work on these beasts, picture that! If anyone wants to mail me about this It would be great too
May 13, 2012
 Followup from the Pelican Staff: Contact one of our parts specialist at 888 280 7799 and they'll help you get the parts you need - Kerry at Pelican Parts  
e30 hobby carComments: I have followed this exactly, i have used as much force as I can muster and I can not get the injectors and fuel rail out! those injectors are stuck in there!!!
any suggestions?
May 12, 2012
 Followup from the Pelican Staff: Try spraying the base of the injector with carb spray. It will libricate the o-rings until the spray evaporates. You can lever up on the rail a little, it is made of metal. Be sure to have spare replacement 0-rings around it case some of them break. - Kerry at Pelican Parts  
AtlantisVIpComments: Would carb/throttle body cleaner be effective for this?
February 28, 2012
 Followup from the Pelican Staff: Yes carb cleaner will work
- Nick at Pelican Parts
chikir1@GPComments: brilliant!!!this tech site rocks,keep up the great work.THANKS
July 11, 2011
 Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
colbyComments: Hi,

I thought brake cleaner was bad for rubber & plastic. I just wanted to confirm that brakes parts clears should be used vs say white gas, for example? Thanks!
February 24, 2011
 Followup from the Pelican Staff: Some cleaners are worse than others - it really depends upon what you use. I agree - you should check the bottle label prior to using it for cleaning anything with rubber & plastic. I've used a whole bunch of stuff in the past with no ill effects, but formulations and products are changing all the time. - Wayne at Pelican Parts  
ethComments: i just replaced mine and this was really helpful. great supplement to the bentley service guide!
August 16, 2010
 Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
bquinn702Comments: #1 disconnect the fuse to the fuel pump, locate that in your manual, #2 start the car and run it till it stalls, #3 open fuel tank.... fuel system is depressurized!!!

your fuel pressure will be the same with a full tank or quarter tank, if it is not then you have a leak somewere.
February 26, 2010
 Followup from the Pelican Staff: Thanks for the additional Info. We appreciate it.
- Nick at Pelican Parts
sunshineComments: How much does it cost to get a fuel injection done on a 2007 328i BMW with 30,000 miles on it?
February 15, 2010
 Followup from the Pelican Staff: The price of the service will depend on where you are getting it done, it could be as low as 75 dollars and as high as 300 dollars.
- Nick at Pelican Parts
MN525iComments: Are they ever going to include pictures in any of their Tech Articles?? People who normally do not do this stuff would have no idea on what they are talking about. Its good info but many need some sort of visual reference...
December 7, 2009
 Followup from the Pelican Staff: Yes, we may be adding some to these articles in the future. In the meantime, there are more on this with photos in our tech articles section. - Wayne at Pelican Parts 
jwade944Comments: Removing the valve cover makes this job a lot easier.
August 31, 2009
 Followup from the Pelican Staff: Thanks for the additional Info. We appreciate it.
- Nick at Pelican Parts
memoriterComments: Just pull the fuel pump fuse, then crank the car until the residual fuel in the lines is used up.

That will de-pressurize the fuel line.
August 6, 2009
 Followup from the Pelican Staff: Thanks for the additional Info. We appreciate it.
- Nick at Pelican Parts
mkstpp989Comments: hey thanks i,ve 100 different sites and yours is the 1st that gives detailed instructions and if they need a pic they shoud,nt be trying this project thanks again
July 31, 2009
 Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
polskaComments: fyi: pics are located on other fuel injector replacement article.
June 30, 2009
 Followup from the Pelican Staff: Thanks for the input on this one. We appreciate the help.
- Nick at Pelican Parts
AjanComments: Hey Pictures worth thousand words ...
April 22, 2009
 Followup from the Pelican Staff: Thanks for the input on this one. We appreciate the help.
- Nick at Pelican Parts

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