Sounds like the gauge cluster is the culprit. Google "BMW E46 hidden obc functions." One of the tests is a test of the gauge cluster. It will "exercise" the gauges and flash all the indicators. If the fuel level gauge works you may have a wiring problem. I've owned BMWs since 1974 and I've noticed that the quality of the wiring has gone downhill with each model I've owned. If it is the gauge there are companies that'll repair the gauge cluster.

 

Just tried it. I was hoping it didnt move but it did. I guess I'll have to chase the wiring and see where that leads me. Sucks to need to do this when I have no garage.

You have 2 sensors,one left and one right under the rear seat.

Damn. You're right. and I just looked on ebay, right fuel pump only $40? Looks like I'll be buying 1 of those. Thought it would be way more money. Left fuel sensor cost me twice as much.

 

You have 2 sensors,one left and one right under the rear seat.

 

Wait...doublecheck that. The fuel pump is more expensive than the level sensor. The FB should cost more than $40...not sure of price of the fuel sensor on left side of tank, but know some have removed the level sending unit and cleaned it up so it worked.

Anyway, FB should be more than the leveling unit on the left side...I'm pretty sure.

D

 

The left one I bought was genuine BMW. Cost me about $83

The right one im looking at, is not. Actually they're $40-$55. Im kinda hesitating now. They're from brands I've never heard of, Global automotive, Keylife, Eurasia parts? One of them has a lifetime warranty but its probably BS.

 

I forget who the OE maker is, but not any of those names. Get the OE maker, though. Someone will know. If not, I'll check the old one I removed from my car at 185,000 miles (it was still working then!). Sounds like your issue is only on the left side...and you might try cleaning your old one to see if you can get it going. I run Techron a few times a year to keep things clean...one guy, I recall, cleaned that level sender with straight techron...I think. Anyway, unit is probably not returnable, but it might be...if so...try cleaning it.

 

I ran techron once but probably didnt do it right. I believe im supposed to put it in the tank when its almost empty, its kinda hard to tell when its almost empty when fuel gauge doesnt tell me lol. I think I had like half tank at the time. I will try it again though.

Why do you think the left side is the problem? I connected the new sensor to the left without putting it in the tank, moved the floater and nothing happened.

The OEM supplier of fuel pumps is Siemens/VDO. I bet they made the sensors, too.

OP, don't buy aftermarket parts for the fuel system. They will die and leave you stranded a zillion miles from nowhere! Go to bmaparts to buy a new fuel pump.

Thanx. Found a siemens for $120. Gonna try a couple other things before I buy it.

You can check your level sensor outside of the fuel tank.

Use your Digital multi meter and measure the fuel level sensor resistance. Measure the full and empty resistance.

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Did you do a cluster reset?
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Thats a great idea!

Cluster reset? Do you mean, when all the lights come on, and all the needles move? If so, I did that and the whole cluster works fine.

 

The OEM supplier of fuel pumps is Siemens/VDO. I bet they made the sensors, too.

OP, don't buy aftermarket parts for the fuel system. They will die and leave you stranded a zillion miles from nowhere! Go to bmaparts to buy a new fuel pump.

 

You can check your level sensor outside of the fuel tank.

Use your Digital multi meter and measure the fuel level sensor resistance. Measure the full and empty resistance.

.

Did you do a cluster reset?
.

 

BMA Parts always has good fuel pump pricing

It's probably the issue.

 

The wiring to routed to the fuel sensors under the rear seat can be easily damaged. Check both sensors with a multi meter. If the readings change on the sensors when they are moved then look elsewhere.

One of my cars needed a section replaced after a heavy load was placed on the back seat. The sensor wire had broken internally, but the fuel pump power wire was ok.

 

Related question:

Does anyone know why, in the hidden OBC menu, it specifically stats "left half sensor input" and in this thread, it is drastically different from the "right sensor input"? Shouldn't both readings be identical if everything is working properly? Thanks!

Example:

6 Fuel Level sensor inputs in liters
6.0 109330+ Fuel level averaged; Left half sensor input=10.9 liters; Right sensor input=33.0 liters
6.1 0439+ Total tank level averaged; vlgs 6.0: 10.9+33.0=43.9 liters

 

There are 2 sides to the fuel tank with the hump inbetween. The jet pump flows fuel from the left side into the right side.

 

There are 3 functions to the fuel level test.

6.0. Fuel level averaged
6.1 Total tank level.
6.2. Indicated value and tank phase; 1,2 or 3.

 

Why do you say the levels should be equal? There are 2 sides to the tank.

 

why wouldn't they if the car was level?

based on what you said about the 3 values, how am I supposed to be able to determine which side might be faulty?

I know my right side is good because I replaced the fuel pump not long ago, suspect it is driver side fuel sender, wanted to confirm with OBC function..

is it that if the average is lower than the total tank volume, you know something is wrong, but cannot pinpoint it to one side or the other? what are the indicated values phase 1, 2 and 3?

 

You missed my comments above.

There is a hump in between the 2 sides keeping fuel from moving from one side to the other. That is why you need the jet pump to take it from the left side to the right for pickup by the fuel pump.
X_6.2 where x= 1,2 or 3.
1=both sides OK
2= one sensor faulty
3= Implausible input

 

OK, you are being very helpful here, I am still trying to understand though. This is the fuel level sender (left side). How on earth is there any sort of pump on this piece that would move fuel from the left side of the car to the right? It appears to only be a level sensor.

https://www.fcpeuro.com/products/bmw-fuel-tank-sending-unit-level-sensor-e46-16116768788

 

Here is an example of the suckling jet pump attached to the level sender unit.

 

#3 here is the jet pump (16146755880)

 

ahh ok, I fully understand this now. Appreciate all the help with diagrams and pics... so sending pump is inside tank, and hose from that sending jet pump attaches to underside of the sending unit. And since this rarely malfunctions, it is not included in the replacement sending unit from what I can see, correct?

edit: just checked and the sucking jet pump is a $105 part so def does not come with new sending unit.

 

I think you've got it now. See there is no way.for both sides to be the same except when your tank is greater than about 2/3 of the tank when the level is above the hump.

Now you can figure out any fuel level issue you may have.