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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 07-26-2010, 05:52 AM   #1
Registered User
Join Date: May 2009
Location: Netherlands
Posts: 208
My Ride: BMW E91 335i
DIY HOWTO: Change fuel injectors on a E46 325

Hi guys,

Yesterday i was able to change the fuel injectors (FI) on my E46 325ti Compact; under the hood the same as a 325.

I have no mechanics background; i know a little bit on how the engine works, what some of the parts are and i can do an oil change. I've helped with changing the spark plugs once, so i knew roughly what was required for the injectors.

Sorry that i didn't take any pictures of the process, but all in all, it took us about 2.5 hours. It was me , my father and brother, who both have some mechanical skills, but they had never seen the FI change done either.

I performed this outdoors, with a chance of rain ! Not the best circumstances, but just to show you it can be done pretty much anywhere. thank god it didn't rain on us though. I waited a little bit to let the engine cool down. You're leaning on and touching the engine itself. It it's too hot, you're bound to get burnt. I waited about 45 minutes after arriving at the scene.

My car has an ESS tuning supercharger and it comes with a custom intake manifold. That is and looks different than the OEM manifold. Not sure if it affects how the fuel rim is secured on the intake manifold. ESS has spacer rings.

Okay. Here are the steps.

(1) Open the hood. If this comes as a surprise to you, maybe you shouldn't try to change the fuel injectors yourself on your BMW.

(2) Remove the cabin air filter and cover, so you can easily access the top engine cover. The interior filer can be removed by first removing its own cover, which are 3 "spring" screws, which need to be turned 90 degrees. When that cover has been removed, you can clearly see the filter itself. Take it out as well.

(3) On the front of the bottom housing that is now exposed , you see that a battery cable going from the left to the engine and another ribbed cable going all the way across is inside a casing. The casing comes off by unlockin 4 clip type locks, just use a little flat head screwdriver to pop it loose.

(4) After the filter has been removed, remove the bottom part of the cabin air filter housing. This is done with 4 screws that need a special inbus type screw (size 4 i believe). Although you can completely remove the screws, there's no need; it's designed to actually keep the screws attached and still be able to remove the complete housing.

(5) Okay, now you should have a clear view of the top of the engine cover. There should be two small lids covering up the actual screws. Remove the clips (use a flat head again) and use a socket wrench (10 i believe) to remove the engine cover completely.

Allright now you see the actual work ahead. The iron bar on top is pressing onto the 6 fuel injectors. You can see the power supply to the fuel injectors sort of on a 45 degrees angle. The actual fuel pipe (the square iron/aluminium bar) is pressing down on the injectors.

(6) Remove the two clips that hold the eletrical cables on top. First pop out the electrical wirting ,the remove the clips itself. Squeeze the clips and push it out of its fitting. Just use your hands here to avoid damaging the cables or clips.

(7) TRICKY STEP !!!! Now remove the power sockets of the injectors; all 6 one at a time. If you look closely, you'll see a little iron thread clip around the plastic cover. Look at your new injectors, you can see it has 2 little arms which will sit in the openings. Gently use a small flat head screwdriver to push the iron clip on the left away. Notice that if you were to loose the iron thread clip , it would most likely jump into the engine area below and be lost forever. When i did it, the clip would push away and the other side would stay at its place.

(8) When you have done all 6, you can now use your hans and push the socket out of the fuel injector. It takes a little bit of force, but you don't need to bench 300+ pounds to do so. Remember that screwing up here will be a serious pain. Take your time with step 7 and 8.

Now the only thing left to do is removing the 4 screws that is pressing down the fuel injectors into the engine. the 4 screws on my ESS Tuning intake manifold were sitting on a spacer ring. One of them actually fell down into a gap inside the engine. It took a lot of luck and a spaghetti tong to retrieve the spacer again. Try to avoid this by covering the gap when you go ahead.

WARNING: fuel will leak in the next steps !
I think all in all i lost maybe 50 ml of fuel, not much. Just enough to notice and not enough to make you reach for the fire extinguisher.

(9) TRICKEY STEP !!! I removed all 4 screws and spacer below from the fuel rim. Take your time, don't loose anything !

(10) Once the 4 screws are removed, you can gently pull up the whole fuel rim. The injectors will stay connected to the fuel rim. We'll remove them in step 11.

(11) Remove the fuel injectors from the rim. You can use a flat head again to gently pull back the little metal clip. Notice first how it hold the injector in place. Also notice that you can freely turn the injectors around.

(12) Now you can put in the new injectors. Firmly push them in the little round socket of the fuel pipe. Put back the clips on them. We used finger power to push the clip back, but some needed a pipe wrench. Visually inspect the clip is correctly gripping the injector and also the rim of the socket.

(13) Place the rim with the new injectors back over the wholes. Makes sure they sit perfectly over the hole. Turn the injectors so we can soon reconnect the power.

(14) TRICKY !!! Reconnect the fuel rim to the intake manifold. Don't forget the spacers. And don't drop them

(15) Reconnect the power. Make sure the little iron thread clips are also back in position.

DANGER !! We're about to start the car up again. Make sure the fire extinguisher is handy now. Have another person with you, also to help rev the engine and as an extra pair of eyes to find leaks.

(16) It's now time for a little test. Start up the car and have another person also check. Rev the engine and hold on 3- 4000 rpm to increase fuel pressure , assuring there is no leak

Once all look fine, you can reassemble the other steps. in reverse order. Make absotely sure you don't end up with any "spare parts" at the end.

Make a test drive . I also have an OBDII connector for my laptop, which i used to check for misfires or anything. Mine was clean. Thank god.

Tools used:

- Magnet on a stick to retrieve screws or spacer that may fall.
- Fire extinguisher (just in case)
- pipe wrench (to squeeze the clips onto the injectors to connect to the fuel rim)
- socket wrench
- inbus screwdriver
- flat head screw driver
- spaghetti tong (optional )

legal notice: in no way am i responsible to any damage you'll do to your car. I've tried to write down how i did it, and i found out it wasn't that hard. I hope this can serve as a guideline for other thrillseekers like me, who are too cheap to pay the dealership the $100 to have it done.

Have fun !


BMW E91 335i soon with rb turbos, currently on 360 wHP

Last edited by DubVersion; 07-26-2010 at 08:11 AM.
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Old 08-29-2012, 02:55 PM   #2
Registered User
Join Date: Sep 2011
Location: New York
Posts: 9,474
My Ride: '04 330Ci
I would add one step of caution. When the fuel rail is replaced and all connections are made, you might power up the engine without starting it to engage the fuel pump to pressurize the fuel rail. At this point leave it under pressure for a minute or two while you check for leaks rather than starting directly and checking for leaks then.
No sense in running the engine immediately if you might discover a leak before you get things hot.
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Old 11-24-2012, 02:32 AM   #3
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Join Date: May 2012
Location: Anchorage
Posts: 104
My Ride: 2001 325xi
Should I take off the negative battery terminal when doing this? Do I have to?
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Old 11-24-2012, 09:45 AM   #4
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Join Date: Sep 2011
Location: New York
Posts: 9,474
My Ride: '04 330Ci
I didn't.
If you are certain no one will be trying to start your engine while you are working on it, little downside. Not necessary from a safety standpoint. Worst that will happen is you power up the pump and spray gas around. But who would do that?
Hide your keys away when working.
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