Fuel Level not correct

[elrichmeister]

Currently having issues with my fuel level sensors, its reporting unusually high. Indicating above 1/2 the tank at 177 miles since my last fill up. It used sit well below 1/2 around that mileage.
There are 2 fuel level sensors and 2 sides to the fuel tank.
- When the key is on pos 1 fuel level sensors were Left-120 and right-310
- When key position 2 i think the fuel pump primes? The sensors then indicated Left 108 and Right 330. Right side stayed solid 330 i think thats max reading.
- When starting the engine the sensors then indicated Left 045 and right 280

My dumb question is:
Does the right side always have more fuel than the left? Also, is my right side fuel level sender failing?
Here is a video i took of the process

https://photos.app.goo.gl/j5osJSbrVZ6rQS4M8

[jet_dogg]

Are you having an actual problem or just neurotic about the readings?

There's only one sender and that's on the driver side, fuel pump is on the passenger side.

[bmwfnatic]

Definitely not supposed to move around like that.

[elrichmeister]

Are you having an actual problem or just neurotic about the readings?

There's only one sender and that's on the driver side, fuel pump is on the passenger side.

On cold start the fuel level is a bit erratic it eventually settles but fuel level stays pretty high i've seen it stay above 1/2 mark at 200 miles on my trip meter.
I typically always fill up the car when it reaches 1/4 mark which is usually at 220-240 miles or so.
So currently im tracking fuel by mileage rather than fuel level which is kind of annoying. Currently the car is around 210 miles and is starting to go below 1/2 way mark on fuel gauge. Going to see how low the fuel level gets, but worried about running out of gas lol.
The car gets about 18 mpg so theoretically i should 298.8 miles since the tank is 16.6 gallons. Ill drive it to about 250 or so and see where the fuel level is at.

Isn't there 2 level senders? or maybe i'm calling them the wrong thing. There is a Level sender on the left side that's by itself and another one on the right that connected to whole fuel pump assembly right?

[eacmen]

There are fuel level senders on both sides of the vehicle. The passenger side is a pump and a sender, the drivers side is just a sender and “sucking jet pump”.

[Slideways]

On cold start the fuel level is a bit erratic it eventually settles but fuel level stays pretty high i've seen it stay above 1/2 mark at 200 miles on my trip meter.
I typically always fill up the car when it reaches 1/4 mark which is usually at 220-240 miles or so.
So currently im tracking fuel by mileage rather than fuel level which is kind of annoying. Currently the car is around 210 miles and is starting to go below 1/2 way mark on fuel gauge. Going to see how low the fuel level gets, but worried about running out of gas lol.
The car gets about 18 mpg so theoretically i should 298.8 miles since the tank is 16.6 gallons. Ill drive it to about 250 or so and see where the fuel level is at.

Isn't there 2 level senders? or maybe i'm calling them the wrong thing. There is a Level sender on the left side that's by itself and another one on the right that connected to whole fuel pump assembly right?

Yes, there are two. The passenger side has the fuel pump built into the unit. Fuel should always be transferred to the passenger side of the tank. The level sender contacts can go bad and give an incorrect reading. They are getting to 20+ years old at this point.

[Fresh1179]

I apologize, but I am going by memory from a "recent" (couple years ago) secondary pump installation. As I recall, there is only one sender that is located on the driver's side. The driver's side also contains the "sucking jet pump" which can cause issues for people. During the installation of my secondary pump, there was a lot of information on how to correctly index that pump such that the readings are correct and the float is not impeded causing incorrect readings. My recollection is that the pump primes when the vehicle is unlocked and the user opens the door. I am not around my car, so I can't confirm that, but I know there is an audible sound at a certain point from the regulator which is located next to the filter on left side of vehicle.

I think you may be chasing a dragon here, which I have done with this car many a time. It sounds like you have the correct equipment to test fuel pressure during operation. I would simply check that reference value against the expected value to rule out any fuel pressure issues. As to the fuel level, I would first check to see if my sender is oriented in the original direction, such that the level readings are not impeded by any potential snagging issues within the fuel tank. Top it off as much as I can, then make certain my gauge reading is full (with a top off the fuel level will be slightly above the full mark). At that point I know that my pump is putting out proper pressure, and my sender is oriented correctly, and giving me a a correct reading. Then I would simply drive the vehicle. If the level is jumping around, I have a sensor issue, or by some unfortunate chance, a wiring issue and so on. At that time I would purchase a new sender, and try again. Still issues.... then you continue down the rabbit hole. Given the fact that you are competent enough to take a number of fuel pressure readings, my supposition is that you already know everything that I have written out, but I think it is a sensible way to approach the issue. After that, I would make sure I had a new filter. Check again. Still failed? New fuel pressure regulator (Radium actually makes a great one where you can actually view the dial at the regulator) and check the connections at the regulator. Vacuum lines. Flush fuel lines. New injectors. On and on and on.

Good luck, I know this is a frustrating issue. If you google Bimmerworld E46 secondary fuel pump you will get access to lots of threads that contain information on indexing their secondary pump, but they also include a lot of pictures of the OE pump in it's normal position. My concern is that our senders index based off a plastic tab around the "top ring" area, but I would certainly check.

I hope this is helpful in some way.

[elrichmeister]

I apologize, but I am going by memory from a "recent" (couple years ago) secondary pump installation. As I recall, there is only one sender that is located on the driver's side. The driver's side also contains the "sucking jet pump" which can cause issues for people. During the installation of my secondary pump, there was a lot of information on how to correctly index that pump such that the readings are correct and the float is not impeded causing incorrect readings. My recollection is that the pump primes when the vehicle is unlocked and the user opens the door. I am not around my car, so I can't confirm that, but I know there is an audible sound at a certain point from the regulator which is located next to the filter on left side of vehicle.

I think you may be chasing a dragon here, which I have done with this car many a time. It sounds like you have the correct equipment to test fuel pressure during operation. I would simply check that reference value against the expected value to rule out any fuel pressure issues. As to the fuel level, I would first check to see if my sender is oriented in the original direction, such that the level readings are not impeded by any potential snagging issues within the fuel tank. Top it off as much as I can, then make certain my gauge reading is full (with a top off the fuel level will be slightly above the full mark). At that point I know that my pump is putting out proper pressure, and my sender is oriented correctly, and giving me a a correct reading. Then I would simply drive the vehicle. If the level is jumping around, I have a sensor issue, or by some unfortunate chance, a wiring issue and so on. At that time I would purchase a new sender, and try again. Still issues.... then you continue down the rabbit hole. Given the fact that you are competent enough to take a number of fuel pressure readings, my supposition is that you already know everything that I have written out, but I think it is a sensible way to approach the issue. After that, I would make sure I had a new filter. Check again. Still failed? New fuel pressure regulator (Radium actually makes a great one where you can actually view the dial at the regulator) and check the connections at the regulator. Vacuum lines. Flush fuel lines. New injectors. On and on and on.

Good luck, I know this is a frustrating issue. If you google Bimmerworld E46 secondary fuel pump you will get access to lots of threads that contain information on indexing their secondary pump, but they also include a lot of pictures of the OE pump in it's normal position. My concern is that our senders index based off a plastic tab around the "top ring" area, but I would certainly check.

I hope this is helpful in some way.

Thanks for the response, I wasn't actually testing fuel pressure yet, i don't think i have any issues with fuel pump pressure, but great data to have though. Readings are from the OBC test for the fuel level sender that measure the liters of fuel.


So i also have Non-M e46 coupe and checked the fuel level sender test. So the level on that car seem more stable, and when you run the engine more fuel does end up on right side im assuming the jet sucking pump pulls most of the fuel into the right side when running.

I think i just have some finicky level senders, ill look into replacing them eventually.

Another question, should i bite the bullet and get the Genuine BMW right side fuel pump\level sender assembly? its about 2x the price of other models.

[sapote]

1. I apologize, but I am going by memory from a "recent" (couple years ago) secondary pump installation. As I recall, there is only one sender that is located on the driver's side. The driver's side also contains the "sucking jet pump" which can cause issues for people. During the installation of my secondary pump, there was a lot of information on how to correctly index that pump such that the readings are correct and the float is not impeded causing incorrect readings.
2. My recollection is that the pump primes when the vehicle is unlocked and the user opens the door. I am not around my car, so I can't confirm that, but I know there is an audible sound at a certain point from the regulator which is located next to the filter on left side of vehicle.

1. Definitely it has two level senders -- left and right volume. If it has only one sender then how the computer displays the total volume on the gauge?
2. You are thinking the SMG pump. Fuel pump only prime when key turned ON.

[sapote]

Does the right side always have more fuel than the left?

Yes right side always more than left unless the pump is weak and dying.

[Fresh1179]

1. Definitely it has two level senders -- left and right volume. If it has only one sender then how the computer displays the total volume on the gauge?
2. You are thinking the SMG pump. Fuel pump only prime when key turned ON.

I stand corrected. My bad.


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[ATB88]

This weirdness with inflated fuel level vs mileage has actually been happening to me too in the last 6 months. Nearly got stranded once because of it. The driver's side sender/sucking jet pump thing is pretty much the only thing in my fuel system that hasn't been refreshed. My actual fuel pump assembly is pretty new, so I'd assume that the driver's side unit is the issue.

[Fresh1179]

Thanks for the response, I wasn't actually testing fuel pressure yet, i don't think i have any issues with fuel pump pressure, but great data to have though. Readings are from the OBC test for the fuel level sender that measure the liters of fuel.


So i also have Non-M e46 coupe and checked the fuel level sender test. So the level on that car seem more stable, and when you run the engine more fuel does end up on right side im assuming the jet sucking pump pulls most of the fuel into the right side when running.

I think i just have some finicky level senders, ill look into replacing them eventually.

Another question, should i bite the bullet and get the Genuine BMW right side fuel pump\level sender assembly? its about 2x the price of other models.

A lot of people will crucify me for suggesting anything other than Genuine BMW parts, however, the VDO sending unit is OE for our cars according to FCP Euro. Half the price for an OE part. I tend to go that path.


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[dukeofchen]

I've also been going off of mileage because of unreliable readings below 1/4 tank for a while, but haven't dug into it yet.

I'm fairly sure it's the measuring lever arm or contacts on the passenger's side tank, as the issue did arise after I installed a Radium kit retaining the original pump housing. Hopefully I didn't completely bungle the housing when maneuvering the pump back in, but it's a pretty simple mechanism so I don't expect it to be terminal for the housing.

Interestingly I recently ran a bottle of Techron fuel system cleaner for maintenance reasons, and noticed that the inaccurate readings are now happening even at 1/2 tank+, which would again seem to point to the lever arm or contacts.