DIY: Diagnosing and Replacing E46 Fuel Pump

[JEmric]

Yesterday while driving home from work, my 2002 330i started driving strange, first like it was dragging, as if a brake caliper had gotten stuck, but that wasn't the problem, nor the tires being low, so I drove a little more and then noticed a significant lack in power, enough to cause the transmission to shift very oddly, mainly holding gears when it wasn't necessary. I finally noticed that it felt like a bad misfire that was causing my bad drive, so I made it into my garage before the car died and didn't want to run again. At first, it would start, and run really bad, then die unless I held the accelerator all the way down. Then, it just wouldn't start at all. After scanning for codes, I found P1083 and P1085, which say the Fuel Mixture Level is Low, indicating starvation for fuel.

FEAR NOT!!! If you don't have a fancy scanner, you can still narrow down your problem to the common fuel pump failure with absolute certainty. This instruction list will include how to test your fuel pump and ensure it has indeed failed, and how to replace it.

Tools needed for testing: 1/4" socket driver, 10mm socket(s) (short socket at least, but long is helpful too), small flathead screwdriver (or similar object for pushing down shraeder valve), test light (or volt meter), a good supply of paper towels or disposable rags, a helping hand.

1. Start by going under the hood and removing the fuel rail cover (not the valve cover). This is the long and narrow plastic cover that is top dead center on top of the engine, and is removed by first popping off the 2 plastic bolt covers (front and rear, the small flathead screwdriver is useful here), then removing the (2) 10mm bolts holding the cover down. The rear bolt is a little tight under the cabin air filter housing, but the bolts are short, so it comes out easily. Once loose, grab the passenger side edge, lift and pull.
2. Now you can see the fuel rail. Near the front end, you will see the service port. Unscrew the cap to the service port, and do not lose it. It must go back on. Now, get your paper towels or rags to absorb the fuel that comes out, and using the small flathead screwdriver, push down the pin in the middle of the port until no more fuel comes out, using your rags to absorb the fuel lost along the way. Approximately 1/4 cup of fuel should come out, at most. This will relieve the pressure in the fuel system, ensuring it will need to pressurize later when you go to test.
3. Now go inside and remove the rear seat bottom by giving a gentle upward tug on the front edge of both the driver and passenger side. Once you hear the pops of the clips on both sides disengage, lift and pull forward. Don't worry, it's light. In sedans, the seat bottom can easily be turned up and removed from either side, in coupes, it takes a little more careful maneuvering, and in cabrios...Put the top down before you start.
4. On both sides, you will see wire that comes from the side of the car and disappears into a large rubber grommet about a foot in. You are only concerned about the passenger side. If you have an extra wire that's not connected to anything, don't worry about it, just work around it. Get under the edge of the large rubber grommet with your fingers and pull it out. Once the grommet is out completely, you will see the rest of the wire going to the fuel pump, there's about an extra 10" of wire that can come out.
5. Now, lift up the edge of the carpet slightly where it meets the insulation pad, then you can lift and pull back a flap(about 12" square) that is already cut into the insulation pad. This will expose the body plate that covers the fuel pump, along with the (4) 10mm nuts that attach it. Remove the nuts, then put your finger in the hole and pull up then set the plate back out of the way with the wire running through it. Be careful with the foam gasket around the edge of the plate, it can stay in place, just don't mess it up.
6. You can now see the wiring harness and outlet line at the top of the fuel pump. To remove the harness, take your small flathead and gently pry between the harness and it's clip to slide the clip back about 1/2" (10mm), then grab the sides of the slide clip and pull up. You should now have the wiring harness in your hand.
7. In the harness, you should 2 longitudinal rows of pin connectors, one row has two pins right next to each other, and one row has a gap between the two pins. You're interested in the row with the two pins right next to each other. This is where the buddy comes in (I mean aside from holding your beer). Get a good ground with your test light or meter (I used the stud the nut was on holding the body plate cover on), then stick your probe in one of the two pins right next to each other. Have your buddy turn the key to the run position, but don't crank. Your test light should come on (or show battery voltage if using meter) for 3 to 5 seconds. If no light, turn key off, stick probe in other pin right next to it, and repeat. If you get no light (or voltage) in either pin connection, you have another problem you must fix first as there is no power being sent to the pump. If you do get the light, that's good, turn key off, move to the next step.
8. Now reconnect the wiring harness by pushing straight down onto connection on pump. Once it goes clips on, slide clip closed. Now have your buddy turn the key to the run position again, and you should hear the pump run (a low volume high pitched whine) for 3-5 seconds. I used a stethoscope to ensure I could hear it right. If you don't hear the pump but you got the light in the last step, your pump is dead. If you do hear it, you have another issue.

To replace the pump, you will also need: a good pair of pliers or sidecutters (to remove the crimp-type hose clamp that BMW loves), a large flathead screwdriver or good pry-bar, a hammer, a knife, something to plug the fuel line and something to cap the fuel line connector, some non-chlorinated brake parts or electrical parts cleaner, a bucket (to put old pump in once removed), more paper towels or rags, a new fuel pump, a small hose clamp.

9. Be sure you're working in a well ventilated area, roll down all windows and open sunroof. Ensure key is off and removed, then remove the harness as you did in step 6, and set aside. Next, use cutters to carefully destroy the crimp type hose clamp to remove. To me, this was the hardest part of the job. Be mindful as that connection under that hose is plastic and will break, but I exerted some force in destroying my clamp to get it off, with no problem. Once clamp is off, remove hose ( you get a few drops of fuel out of here, but this is part of the reason for relieving the fuel pressure at the rail in the first 2 steps, so it doesn't spray you like a territorial cat) and plug hose end, then push aside.
10. Next, use brake or electrical parts cleaner sparingly to remove most of the dust/dirt around the edge of the fuel pump, focusing on cleaning up the big metal ring. There's a goopy glue blob adjacent the little finger handle that will get really soft and very sticky with cleaner, so be aware of that as you're working around it. Then, use rags/towels to absorb and wipe down excess fluid. Now use your knife to cut goopy glue blob adjacent the little handle. Be sure to try to separate the blob from the big metal ring around the edges.
11. Now get your hammer and big flathead screwdriver. By now, you should've noticed the big metal retainer ring has little ridges around it. Using your screwdriver set on one of the ridges, whack the butt of the screwdriver with the hammer. It will take some good hard blows, and quite a few of them to get this ring to turn. Be mindful of the fuel line and anything else that might be in the way, and most importantly turn the ring COUNTER-CLOCKWISE! You may have to switch from side to side and work your way around the ring a bit. Once you've gotten about a full turn out of the ring, you should be able to spin it by hand until it comes off, about another 3-5 full turns.
12. Now get bucket ready, then put finger through little handle and give a gentle upward tug. Once pump assy. pops loose, pull up slowly. On the front side, there is a flex hose you have to help out of the hole. After that, just work it up. The float arm for the level sender faces the passenger side, so you will have to tilt the assy. to get this out. The large rubber O-ring may or may not come loose with the pump. If it does, take note of orientation and put it back in place before installing new pump. Once out, place dead pump in bucket and set aside.
13. Now you're ready for the new pump. Remember to tilt towards passenger's side to get sender float arm in first, then gently work into hole. Make sure the O-ring stays in place as you're putting the new pump in. There's a notched edge at the back of the hole for alignment of the top of the pump. The pump should kind of pop into place. Then screw back on large metal ring. You should be able to get a few (clockwise) turns by hand, then use hammer and screwdriver to get ring in about same orientation with goopy blob adjacent the little handle. Again, this will take several good hard blows, but you want this ring tight.
14. Now remove plug from fuel line, place clamp on hose, then reattach hose to connector on pump body and tighten clamp, but don't over-tighten. Now reattach the wiring connector, ensuring it is still going through the hole in the plate. Next, get in the command seat and turn key to run position, And now you should be able to hear the pump run for 3-5 seconds. Cycle the key on then off 2-3 more times, leaving in each of run and off positions for about 5 seconds. This will ensure you've completely primed the fuel system (repressurized it). Now start 'er up and see how it runs. Run for a couple minutes, and check for leaks around the newly clamped hose connection. Once everything is good, shut it off and go back to the hole.
15. Now reattach the body plate with the (4) 10mm nuts, but don't overtighten and strip. Just a little past hand tight will due fine. When the plate is facing up, you can see a little point stamped into it, the point faces the front of the car. The plate will only go on one way. Next, lay the pad back over the plate and ensure front edge goes under carpet. Then, put grommet back in body plate hole. Put one side in grove lip, then push down as you roll around the grommet til it's back in place.
16. Finally, put the seat bottom back in. But before you do, this would be a good opportunity to vacuum underneath the seat since you have it out. Make sure the seatbelts and buckles come up into their respective slots, and that the plastic covers for the child seat anchors go on last. Make sure seat bottom is in correct position and all the way back before pushing down on front edge to engage the clips. Once your hear the two pops, JOB DONE!!!

Clean up, put everything away, and then go enjoy the drive. If you leave the pump in the bucket for a few days, all of the liquid fuel will evaporate. More fuel in the tank when you do this equals more that will have to evaporate. Check your local regulations for disposal of dead pump and any excess fuel. I'm pretty sure in most areas it would be a bad idea to bury your dead pump...so don't.

I got a new OEM Siemens/VDO Fuel pump Assembly I picked up for about $160.

[96Beatz]

This was Exact to the "T" This helped me from start to finish! I even registered to the site just to thank you. So thanks!

[JEmric]

You are quite welcome. While searching for some guidance on how to replace the fuel pump, I ran across alot of incorrect or incomplete information. I found numerous posts on forums where people weren't sure if the failure was due to the fuel pump or the relay. I found a video on youtube where the guy cut the insulation padding over the body plate, even though it's already cut for you. And nowhere did anyone mention the goopy sealant on the big metal ring. So I decided to compile all the information needed in great detail in one place since I'm a mechanic by trade.

[Kawasaki Rider]

I read the post with directions to replace the fuel pump, but my 325i does not have a rubber grommet under rear seat. It has two wires but ha metal that is soldered. Could there be different types of fuel pumps or maybe mine is located in a different location. Thanks for any help

[JEmric]

Kawasaki Rider, What year is your 325i? Can you share a picture of what you're describing? I'd be happy to help, and a picture would really help me understand what you're looking at.

[Kawasaki Rider]

The 325i is a 2003 model. The car has been at a repair shop for over 4 months. He says I have to purchase a fuel tank because the fuel filter is inside and no way to replace it. I can't believe that. I am desperate. Thanks

[JEmric]

I hate to say it bud, but I think the shop your car is at is a bunch of idiots. Yes, there is a fuel pre-filter attached to the pump, but it comes out with the pump. The only reason you should ever have to replace your fuel tank is because it's ruptured or cracked, and it takes ALOT of impact force to cause that. I can't think of any reason why the replacement of the pump in your 325i should differ from the instructions I outline. The only think I can think of is that some sort of repair to your vehicle was done improperly at some point in the past. I'd really like to see a picture of the area underneath the rear seat bottom on the passenger side with the seat bottom removed. I believe if you can get that, we can solve the issue you're having.

[Kawasaki Rider]

Thanks for your help. I will try to get a picture tomorrow. Thanks again. I have felt so helpless.

I made a mistake and typed fuel filter in a previous post, but should have typed fuel pump. Is the fuel pump in the tank? If so can you remove it without replacing the tank?

[Automaticftp]

Thanks for your help. I will try to get a picture tomorrow. Thanks again. I have felt so helpless.

I made a mistake and typed fuel filter in a previous post, but should have typed fuel pump. Is the fuel pump in the tank? If so can you remove it without replacing the tank?

Yes. On an E46, the fuel pump is located in the fuel tank, but is accessed through the top of the fuel tank, which is accessed by removing the rear seat as detailed in JEmric's very fine DIY.

There is NO need to remove the whole fuel tank--if a shop is telling you that, they simply don't know what they're talking about.

[mjbwarrior]

I just diagnosed a bad fuel pump in my 01' 330i. Wouldn't start last night at the grocery store. Had it towed home and was losing sleep over it. Got home from work today and went at it until I narrowed it down to a few things and this was on of the few things. I gotta tell you I thought it would be more difficult. Big time thanks for the DIY write up. Couldn't have been more precise.
Thanks man!

[JEmric]

I thought it would be alot harder, too. The hardest part about of when I had to do this is the fact that it was 98*F in the middle of the summer. Glad I could be of service, unfortunately, I don't know how much more I'll be able to help. I've been out of work for the past 6 months and simply can't afford to keep my E46 anymore. I'm out of money and can't afford the payments, I've fallen behind, so I'm gonna have to give it back. Well, it was a fun ride while it lasted.

[latitude39]

I thought you would be alot harder, too. The hardest part about when I had to do this the fact that it was 98*F in the middle of the summer. Glad I could of service, unfortunately, I don't know how much more I'll be able to help. I've been out of work for the past 6 months and simply can't afford to keep my E46 anymore. I'm out of money and can't afford the payments, I've fallen behind, so I'm gonna have to give it back. Well, it was a fun ride while it lasted.

I'm very sorry to hear about your unfortunate circumstances. I read your DIY with keen interest and will use it when I replace my fuel pump.

Good luck in landing a job. Have you thought about advertising your BMW mechanic'ing skills on craigslist? E46 cars are all out of their warranty and maintenance is expensive at dealerships.

Thanks again for adding to the DIY body of knowledge!

[phase888]

Yes. On an E46, the fuel pump is located in the fuel tank, but is accessed through the top of the fuel tank, which is accessed by removing the rear seat as detailed in JEmric's very fine DIY.

There is NO need to remove the whole fuel tank--if a shop is telling you that, they simply don't know what they're talking about.

If I'm not mistaken, SULEV E46's with the M56B25 do have a contained fuel system which requires a whole fuel system delivery replacement in the event of pump failure or filter clogging, right? Some of the 2003's and on fall under this I think. Again, I'm not entirely sure but this post got bumped and I just read this statement which makes me remember reading something about the low emission vehicles and that they had some special requirement with the fuel system. I honestly have no experience in these but I suppose doing some up front research might be called for if you have an M56B25 prior to starting.

[tue22]

First-off , it was well written. That will definitely help a lot of Bimmer owner out there.

Mine is weird.
The fuel pump did not start when I switch the key ON, given my car was running the day before without any symptom like you posted originally.
The weather was very cold (11F, no kidding)
I went to trouble shoot starting with fuse#54 (fuel pump) and ECM fuses (OK)

Then I remove fuel pump connector and checked for Voltage. Wrongly, I measured 2 pins on the row with a gap and got 5V.

So I removed Relay and tested (OK). I can hear actuator kick-in whenever apply 12V on pin 85 and 86

Next I measured pin 30 from Relay board and got 12V (I started spin my head )

So I put back the Relay,give another try to measure Voltage at Fuelpump connector, this time I noticed a flash of 12V when measured 2 pins next to each other, while witching the Key ON

I re-installed the connector and can hear the pump running when switching the key ON. The car started at the first shot. At that time, weather was getting warmer (30F).

Here the questions:
(from you note.7), the Voltage of 2 pins next to each other on the connector should be 12V and last 3 to 5 seconds, then return to zero? (I believe the White -Blue stripe is (+) and Brown is (-))

What is problem of my car at first?
Is it faulty Fuel pump at first?
Is it faulty Relay at cold temp.?
Is it bad connector at the fuel pump? ( given I checked continuity of ground (-))

Thank you all for your comments

Hi JEmric,
In step 14, when re-attach the hose to the new pump. Do I need new clamp? If Yes. What type of clamp you 'd use?
Thanks.

Shoot!. The car did not start this morning , and I could not hear the fuel pump sound either when switch the Key to RUN
I need to find out why exactly before replacing part.

[beamer34]

My 2003 325i was chugging a few days back. I suspected fuel pump or ignition coils. Well then the car drove fine and the next morning it would turn over but not start. My engine is a SULEV M56. I was told my fuel pump is directly attached to the fuel tank. If that's the problem, any suggestions other than a new 7000 dollar fuel tank?

[techedude]

My 2003 325i was chugging a few days back. I suspected fuel pump or ignition coils. Well then the car drove fine and the next morning it would turn over but not start. My engine is a SULEV M56. I was told my fuel pump is directly attached to the fuel tank. If that's the problem, any suggestions other than a new 7000 dollar fuel tank?

You're in luck. SULEV cars have a special warranty that covers emission components for 15 years and 150k miles. Take it to the BMW dealership and find someone there who knows what they are talking about. This will be a free repair for you.

[djmotor]

Pictures pls

[kakalas]

Hello,
I think that my m54b22 pulls off the way it should, especially at high revs. So I decided to make the fuel pressure test. Here are the results:
Injectors pressure Test:
http://www.youtube.com/watch?v=HHyqG5ItAxc

Fuel pump pressure test:
http://www.youtube.com/watch?v=kkynKDTKtXI
Checked vacuum line to the pressure regulator, everything is ok
Does this mean that the fuel pump is coming to an end? or so and should be?

[Nemesiss]

Hi,

On the same topic as this, today my wife got in her car and tried to start it, it wouldn't start. Loads of battery power, just doesn't seem to catch and go. She has been driving it, and had that same day already with no complaints. She was on a road trip with the car a few days ago and said she thought it was using to much gas which has me questioning if the pump is the problem or not.

So, following the many, many, ssooo many threads and advice I figured it could be the fuel pump. The car has 100k on it now and it's starting to show it's age.

I checked the #54 fuse, which was fine. I was going to check the relay and although everyone says it's behind the glove box, I have no clue how to get to it. I also seen some posts saying those rarely fail. I figured I would just do the ometer test on the pump itself. I followed the instructions on this thread, just so happens my ometer is broke and in the morning I will get another. So, as a test just to see if I'm on the right track I had my wife come out and turn the key to the on position while I put my ear to the top of the location of the pump (she thought I was insane) and there was no sound at all. Nothing, not a peep.

Now my question is, if the pump is pressured up would there be any sound of the pump kicking in? Would I be able to hear it like that or is it very quiet?

I've read it could be the relay, it could be the pump, it could be fuses, it could be the fuel filter. I figured for $150 I would replace the pump since the tow truck bill would be a $100 anyone before any work.

Am I on the right track at least? The ometer test would be the definite test I'm assuming. I just thought I should be able to hear it.

thanks.

[EPK910]

appreciate this was a while back.
Did you find out what the problem was with your BMW fuel pump not priming ?
Thanks

[323i jlviii]

Ebay
$43.65
Brand new, complete, works great! Very easy removal and install was just as easy.

Great detailed description above! After it all, Lift out the back seat, close the doors,
LISTEN and turn the key - you'll be able to hear the pump operating, if not, it's probably dead.

Get a high pressure hose clamp before starting it's going to be needed if the pump hasn't been changed,
do the fuel filter too! The pressure will be off ! Gas will still be in the lines! So prepare for it.

New Electric Fuel Pump Gas With Sending Unit 325 323 328 330 E46 3 Series E90

[daughters330i]

Thanks for this excellent DIY. Especially the testing of whether the pump is getting power. As another poster said, this was right on the money!

[OnTheFence]

This was one of the more confusing DIY's I've encountered on this car.
Took me about 3 hours to get this done.
If I did it again, I could do it in 15 minutes.


I will document some of the issues I ran into, to make this quicker for the next guy.
I would set aside 1-2 hours, in case you get stuck on any step.


I pulled fuse 54 and ran the car until it stalled (1-2 seconds max)



I sliced the mat to be able to peel away the mat away from the blocking wire.
You could try to get the four 10mm bolts undone with the mat flopping in the way, and then peel both back together.
However, this was not obvious to me, since I had no idea what I was looking at, since the existing write ups have no photos.



I was unable to lift up the black circle plate
But, since I had no idea what was under there, I got stuck here.
I then noticed the cable was kinked and getting snagged on the rim.
The black plate should pull freely off once the cable harness is clear.



Removing the wire harness clip is simple.
Stick a screwdriver into the clip, and slide it open, and the plug comes up.


Removing the Oeticker clamp is simple. Just peel it back with flush cutters.
Have various hose clamps ready before starting this job, or you will be driving around to various auto stores.


Detaching the fuel hose was simple, especially if you have hose pliers or spark plug pliers.
Way better than using a flat screwdriver.


Removing the sealing ring was a hassle.
I had to hammer the crap out of the notched ring.
A few "taps"? My ass. 4lb mini-sledge and full sized chisel and about 20-30 very hard whacks.
Thought the neighbors were going to complain.
I thought I was going to crack the old fuel pump, but the ring finally started moving.


Removing the fuel pump is easy. Just peek inside and make sure the CRAZY STRAW thing isn't getting blocked.
Also, you'll need to angle the thing unit to clear the fuel level sender and base webbing thing.


Reinstalling the pump took me at least 30 minutes. I couldn't get it to seat. Tried both pumps and neither would fit.
The metal sealing ring would not catch, so I knew the pump was not seated correctly.
I was installing the sealing gasket on the pump and then trying to seat that into the hole.
The "wall of text" write up was not clear on this.
As JMO69 said above, you need to REINSTALL THE GASKET INTO THE HOLE, NOT THE PUMP.
It will seat perfectly into the rim hole and then the fuel pump will fit perfectly flush with a tight seal, all tucked in.
If you try to put the gasket on the pump, your connection will be loose and wobbly.



Took a while to get the rear seat installed.
I finally reached under the seat and tried to feel where the hole was not meeting the prong and tried to line them up.
Anyone know what this thing is for?

[workasusual]

I just want to say Thank you!! You walked me through replacing the fuel pump on my 01 330CI your directions were spot on! Thanks Again!

[OnTheFence]

Glad it worked out for you.
How did you know it needed replacing?