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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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  #1  
Old 04-13-2016, 08:40 PM
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Rocky_Charles4 Rocky_Charles4 is offline
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Fuel Gauge not reading right?

Hey folks, long time no talk. How's everyone?

I recently had an issue with my fuel pump, which in turned caused my car to stall out after starting it. I changed it out for another one. However once I replaced it, I noticed my fuel gauge kept rising as I drove.

I was wondering what might be the cause of this. I added fuel just today as I got off work. And the level never changed. Just stayed the same, a quarter after the middle. I was thinking of changing out my fuel filter as well. I also heard resetting the gauges could work.

Any ideas?
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  #2  
Old 04-14-2016, 09:44 AM
DEADF15H DEADF15H is offline
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Quote:
Originally Posted by Rocky_Charles4 View Post
Hey folks, long time no talk. How's everyone?

I recently had an issue with my fuel pump, which in turned caused my car to stall out after starting it. I changed it out for another one. However once I replaced it, I noticed my fuel gauge kept rising as I drove.

I was wondering what might be the cause of this. I added fuel just today as I got off work. And the level never changed. Just stayed the same, a quarter after the middle. I was thinking of changing out my fuel filter as well. I also heard resetting the gauges could work.

Any ideas?
Did you put in a new Siemens/VDO or genuine BMW pump?
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  #3  
Old 04-14-2016, 02:28 PM
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Rocky_Charles4 Rocky_Charles4 is offline
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Originally Posted by DEADF15H View Post
Did you put in a new Siemens/VDO or genuine BMW pump?
I believe it was the Siemens.

Strangely enough, the meter started to go back down. The sensor might have finally caught up to the actual fuel level. I'll keep looking at it though.

Also, it would be wise to change my fuel filter also eh?
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Old 04-14-2016, 02:54 PM
marcozandrini marcozandrini is offline
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Yes, the filter needs to be change when the pump is changed.
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Old 04-14-2016, 08:53 PM
DEADF15H DEADF15H is offline
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Go to E46Fanatics.com, search poster "jfoj Electronic Fuel Pump PM" for everything you need to know about fuel pumps. He suggests pump, filter, and relay. If doing the filter, replace the hoses while there, they're cheap and you already have them apart.

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Old 04-15-2016, 10:36 AM
tristero tristero is offline
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Another common issue with fuel level is if the float is jammed when you installed the pump.

Also, I've read a lot of instances where people install the seal on the tank, then install the pump. You must install the seal on the PUMP , then install the seal+pump into the tank. Otherwise, the seal won't seat properly, the pump won't be all the way down, and the float won't read properly. You'll probably also get an evap monitor reset problem, if you let it ride in the wrong position.
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Old 04-17-2016, 06:49 PM
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Rocky_Charles4 Rocky_Charles4 is offline
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Yeah okay..I decided to put in about 27 dollars worth of gas. I believe the e46's have a total of 16.6 gallons of fuel. Maybe 17 gallons. So My meter was a tad over a quarter of gas on the meter (4.25 Gallons). Did some math and to fill my tank up would be 12.6 gallons. I put in about 9.7 gallons. I get back into my car started it up and the meter moved up about a tad over half on the meter 1/2.

..Something is off and wrong about my fuel meter. I was thinking perhaps its my fuel sending unit that needs changing as well? I ONLY switched out the fuel pump for a new one.


Also, I put in some Chevron Techron fuel cleaner mixing the gas with it while at the pump.

Correct me if I'm wrong, but the e46 has a Fuel PUMP unit on the passenger side. And a Fuel SENDER Unit on the Driver side?

P.S. Fuel Filter and Fuel lines are bought and on its way.
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Old 04-17-2016, 07:35 PM
Starless Starless is offline
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I believe what you describe is the problem with the fuel sender on the drivers side.
Neither Fuel filter not new fuel pump should have nothing to do with this. That sender unit equalizes the gas between the right and left compartments of the fuel tank. If it does not work correctly you get abnormal fuel readings...
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Old 04-17-2016, 08:49 PM
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Rocky_Charles4 Rocky_Charles4 is offline
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Ah. I see. Makes sense. But I'm still not understanding how the sender is so far off in reading the actual Fuel level. What could possible make it be far off? New pump different size floaters?
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Old 04-18-2016, 08:15 AM
tristero tristero is offline
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It is complicated. no doubt about that.

There is a sender in the right side, and a sender in the left side. Each sender has a float, an arm, and a wiper, which sends a signal as a resistance reading (ohms) depending on how much fuel is in each side.

The gauge gets BOTH signals, (ohm readings), then averages them.

Things that can interfere:
1. Float isn't floating (cracked, filled with fuel).
2. Arm jammed (can't travel up and down with the fuel).
3. Wiper dirty, misadjusted, broken (does not produce the correct ohm level when the arm is at a given level).
4. Connector not plugged in right (no signal).
5. (least common, but happened to me: fuel gauge averaging code is written-over in the DME; if you do the temperature gauge de-buffereing coding in pasoft, but you use the normal 3-series map on a zhp, (or any other incorrect map) all kinds of weirdness ensues).
6. actually very common: Seal on new fuel pump improperly installed, pump is sitting about 1/2" higher than it should, tank not sealed, not sure how this affects reading, but probably will read less fuel than is actually in the tank.

It sounds to me that if both tanks are full, one sender is either jammed, or the float isn't floating, or the connector is unplugged. It stands to reason that this is the sender you just replaced; attached to the main fuel pump.


(here is another complication. There are a ton of variations on this: the car has two tanks, and a transfer pump. Fuel is drawn from the right tank, to the motor, and excess fuel is RETURNED to the left tank. So the right tank is always getting drained. The left tank is always getting filled. That's where the transfer pump comes into play. As you're running the motor, the transfer ppump will try to pump fuel from the left tank to the right. The pump from the right tank to engine is always working, you need to assume that. (or the engine won't run). The pump from the engine to the left tank is also going to always work. The pump in question is the transfer pump. If it fails, you'll run out of gas when fuel is only in the left tank (remaining half tank ful won't transfer). So your motor should die when you're only about 1/2 full. I've never read about this happening, but some people do replace their transfer pump.)
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Last edited by tristero; 04-18-2016 at 08:23 AM.
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  #11  
Old 04-18-2016, 09:43 AM
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Rocky_Charles4 Rocky_Charles4 is offline
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Quote:
Originally Posted by tristero View Post
It is complicated. no doubt about that.

There is a sender in the right side, and a sender in the left side. Each sender has a float, an arm, and a wiper, which sends a signal as a resistance reading (ohms) depending on how much fuel is in each side.

The gauge gets BOTH signals, (ohm readings), then averages them.

Things that can interfere:
1. Float isn't floating (cracked, filled with fuel).
2. Arm jammed (can't travel up and down with the fuel).
3. Wiper dirty, misadjusted, broken (does not produce the correct ohm level when the arm is at a given level).
4. Connector not plugged in right (no signal).
5. (least common, but happened to me: fuel gauge averaging code is written-over in the DME; if you do the temperature gauge de-buffereing coding in pasoft, but you use the normal 3-series map on a zhp, (or any other incorrect map) all kinds of weirdness ensues).
6. actually very common: Seal on new fuel pump improperly installed, pump is sitting about 1/2" higher than it should, tank not sealed, not sure how this affects reading, but probably will read less fuel than is actually in the tank.

It sounds to me that if both tanks are full, one sender is either jammed, or the float isn't floating, or the connector is unplugged. It stands to reason that this is the sender you just replaced; attached to the main fuel pump.


(here is another complication. There are a ton of variations on this: the car has two tanks, and a transfer pump. Fuel is drawn from the right tank, to the motor, and excess fuel is RETURNED to the left tank. So the right tank is always getting drained. The left tank is always getting filled. That's where the transfer pump comes into play. As you're running the motor, the transfer ppump will try to pump fuel from the left tank to the right. The pump from the right tank to engine is always working, you need to assume that. (or the engine won't run). The pump from the engine to the left tank is also going to always work. The pump in question is the transfer pump. If it fails, you'll run out of gas when fuel is only in the left tank (remaining half tank ful won't transfer). So your motor should die when you're only about 1/2 full. I've never read about this happening, but some people do replace their transfer pump.)
Ahhh, I had a theory this was how the e46 was set to be. Right side Fuel side to transfer to the engine to make a circle Back to the left side (Sensor) Side for left over fuel.

I get it now. Looked at a Fuel System Diagram to get more of an insight. I suppose I might as well change out the sender and call it a night. hopefully that solves the bad readings.


I just figured the floaters would be the cause issue of this. Hearing some stories in e46fanatics page about floaters aftermarket ones coming in different sizes or density than the original oem. Which would cause slight or more off readings. So they would detach the floater off the aftermarket unit, and reattach the oem floater with the aftermarket, and presto....New calculated readings. But this kinda changes the game for me. lol
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Last edited by Rocky_Charles4; 04-18-2016 at 09:45 AM.
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  #12  
Old 07-22-2016, 11:04 AM
markab markab is offline
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i'm experiencing the same issues sometimes it reads a half of tank, then goes all the way back to empty and the light comes on me and my buddy replaced the pump and the sending unit, i've also read somewhere that it needs to be reset is this correct and how do you reset it?
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