e53 Fuel Supply Detailed (fuel pump / siphon pump diagnostic help)
 

I definitely approve of the minor change to the reading of the pump side. 1.1 much better. Key element: engine should be running because there is a constant circulation of gas out of the right side back to the left side and back to the right. So that the right side is also constantly spilling over into the left.

I'm not aware of any form of calibration but I'm curious about the low numbers when full even in my case about 10L shy of actual volume.

I filled mine today, right to the brim. The BC readings were:

55.0L/27.0L/82.0L

Which, as you say, seems about 10L short on the actual stated capacity.

@wpoll : with thise readings, where was the needle on the gauge?

The previous time I filled up and insisted after the pump clicked, I got it up to about 80L and and the needle was stil 2 or 3 milimeters below the full mark.

I'm going to browse the various software to see if I can find something regarding the gauge calibration or sender calibration since the math from XXX Ohms to XXX Liters has to come from somewhere and I'm quite sure my cluster is the same as an M5 (4.6is) that probably doesn't have the same tank size (quick google say 70L and 78L). I'll have to check in the software if my cluster is original.
If my gauge is set up for 82 ou 93L (this still is a mystery) but the sender interpretation is set up for 70 ou 78L, it would explain the slight discrepancy. I'm not going to enjoy this considering the cold but I'll try and look into which module reads the sender units.

If it keeps bugging me, I'm going to change the pump and sender assembly but considering the left one is new (3 month old) and straight from BMW and it doesn't register completely full either, I'm perplexed.

I did however notice that while driving with test No6 opened, I see fuel going from left to right more "actively" now the tubes are in the correct place.

After I fill up, the fuel guage needle is buried right to the top - slightly past full. My gauge is marked in litres, with 20 at 1/4, 40 at 1/2, 60 at 3/5 and MAX at full.

I usually drive about 100kms before the needle starts to move downwards at all.

Thanks for that, I'm not sure what to make of it but I'm going to investigate a little more to see what I can figure out but right now its part raining and part snowing so I'm going to wait a little. After all my gauge is false but the right way.

I only went back a few pages...and I didn't see where you did TEST #21 after replacing any components. I'm not even sure if I got the gist of what was replaced...but if your fuel gauge is not reading correctly or your TEST #6 numbers are way off...if you replace a fuel sender...you need to perform TEST #21. This will help with the "damping function" of data. Without a reset it may take multiple fill-ups for the data to correct itself after replacing components that deal with sending fuel consumption data to the IKE.

Also, when you go to the 2nd screen of TEST 6...what are your "PHASE" numbers? Is it PHASE 1, PHASE 2, OR PHASE 3? The "phase" number reveals if one of the fuel senders is not working properly.

Great call on 21. I don't think I get phase info I have the basic dash but for those with the fancy dash that's helpful.


Sent from my iPhone using Tapatalk Pro

Very good call on test 21, didn't do it. When I replaced the left side sender, the resistance plate was broken in half so it went form dead to alive. Second screen of test No6 says PHASE 1.

I'll run it in an hour and report back on the result.

Doing a little research, there is quite a bit of coding values taht can be changed with NCS Expert, including tank capacity and reserve size and when the light comes on. This will be my second test after test 21 if no success.

So after a little bit more testing, still failling...

Test 21 did nothing...

I plugged in my computer and looked into INPA > body > cluster/Kombi.
There is a screen that shows fuel sender values even though they don't show ohmmeter values but its an analog to digital conversion value. Using this I can see that the right side sender is low. The most annoying part (and this is new since I re-seated the pump), is that this and test 06 show that it sometimes go higher (left turn) and almost to full on the INPA scale before settling back down.

Picture was taken parked flat engine running.

http://img.flat4find.com/images/2017...-14_222047.jpg

I also fired up NCS Expert and looked into the coding of the Kombi (KMBI) and there are quite a few values that can be modified including tank capacity, gauge curve (linear or progressive), reserve size (8 or 10L), ... There are also dampening values for the gauge but I didn't want to play with those so as to not panick the needle and risk damaging it.
Mine was correctly coded, using 92L linear and switching to progressive made no change.

I can only find 2 plausible explanations since the gauge is able to go higher than its "resting" limit of around 22L.
1: The float is not floating great and has troubles lifting the arm high enough (like foating below the surface)
2: Something else I haven't thought of but that's why I'm here...

e53 Fuel Supply Detailed (fuel pump / siphon pump diagnostic help)
 

My bet is a bent float arm. It's too bent it needs to be straighter. I'm betting during one of the install operations, the arm got a little more bent than it should be and when the tank is full the base of the arm is angled down too much. Straighten the arm so the arm will push the wiper higher and it will read higher value.

Your test of a hard left turn goes well with my theory. The gas will never be higher than maybe 1" from the top of the tank when level but a hard right will fill the tank to the roof.

How much to straighten that's a tough call. I'm betting the float needs to come down at least 3-5 cm.