Fuel gauge issues

[bubba966]

Friends '95 525iT has a fuel gauge that's erratic. Sometimes it reads right, and sometimes it reads empty.

OBC does still give the correct range when the gauge isn't reading properly.

Nothing else in the cluster is acting weird. Nor is there any other electrical anomalies.

Fuel gauge issues are either the sender, CCM or cluster related if I'm recalling others problems correctly. As the OBC gives the proper range, that leads me to believe that the sender is fine as the OBC would need to get a proper fuel level to give you the right range. And as there's no other electrical problems I'm guessing that the CCM is ok as well.

Is this just a case of need to replace caps in the cluster? Or is there something else that might be an issue?

[Ross]

A corroded connection could do this.

[bubba966]

A corroded connection could do this.

Where?

Though I wouldn't look so much for corrosion as I think it was a southern car for most of it's life. And we don't have much of a rust problem around here. Haven't found any corrosion on the car yet.

But it does seem like the car has seen a lot of heat over it's lifetime based on it's interior condition. I could see a melted connection somewhere...

[632 Regal]

sounds familiar, I fixed the stop light and the fog light fixed itself, next day gas guage worked properly, still does.


Friends '95 525iT has a fuel gauge that's erratic. Sometimes it reads right, and sometimes it reads empty.

OBC does still give the correct range when the gauge isn't reading properly.

Nothing else in the cluster is acting weird. Nor is there any other electrical anomalies.

Fuel gauge issues are either the sender, CCM or cluster related if I'm recalling others problems correctly. As the OBC gives the proper range, that leads me to believe that the sender is fine as the OBC would need to get a proper fuel level to give you the right range. And as there's no other electrical problems I'm guessing that the CCM is ok as well.

Is this just a case of need to replace caps in the cluster? Or is there something else that might be an issue?

[tim eh?]

I have exactly the same problem and I am suspecting the cluster. I don't think the signal even goes to the CCM - according to the schematics it goes straight to a splice where one lead goes to the obc and the other straight to the cluster. So I am assuming since the obc reads ok (*-you can read the actual volume if you unlock the obc) then the problem is somewhere between the splice and the gauge or even the gauge itself.

[Bo525i]

I´ll join the club then, exactly the same is going on with my gauge..

[aston_jag_tech]

go to a salvage yeard, take out a fuel pump sender assembly, check the resistance of the sender yourself and if ok, install that bad boy in your car

[632 Regal]

Krap, mine is wigged out again, lights all work, guage says empty or just above half tank no matter how much gas is in there...full or empty guage is in a world of it's own. Can the sending unit be cleaned or repaired?

[Bo525i]

It can be opened, not that hard.. But if it helps to clean the resistancewires I dunno!

[yaofeng]

My vote is the fuel level sender. Happened on both of my e34's. Fixed by one from ebay.

[tim eh?]

go to a salvage yeard, take out a fuel pump sender assembly, check the resistance of the sender yourself and if ok, install that bad boy in your car


My vote is the fuel level sender. Happened on both of my e34's. Fixed by one from ebay.

I don't understand how you guys conclude this - if the obc gets an accurate reading then how can the sender be faulty?

[632 Regal]

how do I check the OBC for fuel content?


I don't understand how you guys conclude this - if the obc gets an accurate reading then how can the sender be faulty?

[bubba966]

how do I check the OBC for fuel content?

My friend is using the range function along with the knowledge that she averages 20mpg.

Which is why I don't see how it could be the sender if the OBC is getting a signal saying it's not empty when the gauge says it's empty.

Although I'm kind of recalling that she says it's either saying it's got a half tank or is empty. Maybe the sender is going wonky and is giving enough of a signal to the OBC for it to think it's half full while the cluster is getting a worse signal that says it's empty?

Should try to just pull my sender out of my M-Sport and slap it in her Touring...

[tim eh?]

I know there are 2 types of pumps, is the level sender the same?




how do I check the OBC for fuel content?

test #6 and #7 with unlocked OBC (#6 is immediate, the other is approximated... i think)

edit *- mine reads in litres (i think)

[632 Regal]

my range option says almost exactly what the OBC says according to my calculations and the guage that no longer works. Sounds like the sending unit is fubared in some way now.


My friend is using the range function along with the knowledge that she averages 20mpg.

Which is why I don't see how it could be the sender if the OBC is getting a signal saying it's not empty when the gauge says it's empty.

Although I'm kind of recalling that she says it's either saying it's got a half tank or is empty. Maybe the sender is going wonky and is giving enough of a signal to the OBC for it to think it's half full while the cluster is getting a worse signal that says it's empty?

Should try to just pull my sender out of my M-Sport and slap it in her Touring...

[Bo525i]

Well I swapped mine for one from the salvage yard, seems slightly less erratic but still drops to empty about 50% of the time compared to the old where it was 85%..

My next move is to try the fully working sender from my 525 and to see whether I still get erratic behavior.

I´ll keep you posted (½ tank so I gotta use most of that first! :D)

[Kibokojoe]

yes it helps to clean the wires. I use a cotton ball and contact cleaner

[632 Regal]

pumps on top, fuel level shouldnt matter?


Well I swapped mine for one from the salvage yard, seems slightly less erratic but still drops to empty about 50% of the time compared to the old where it was 85%..

My next move is to try the fully working sender from my 525 and to see whether I still get erratic behavior.

I´ll keep you posted (½ tank so I gotta use most of that first! :D)

[Bo525i]

You still have to stick your hands into the gas to release the pump/sender unit from the base.. So I´ll wait! ;)

[Bo525i]

So, finally got around to changing fuel pump and the sender units, not from my 525 as the pump differs but from a 95 540 @ the salvage yard.. Now the gauge works like it should and as a bonus the obc now reads below 8 liters on obc code 7, got a reading of 4.4 liters after installing the new units (not on code 6 tho, that still reads 8 liters) Never had it do that before! :)

Another thing that I found was that my old pump wasn´t seated properly lacking about ½ inch on the right side looking into the tank, so be thorough and seat it really well by pushing a bit hard when you have to reinstall the pump! ;)

[Kibokojoe]

Yes the sending unit can be removed, opened and cleaned. I did this a month ago to my sons 735i. There is a posting on this sight. On thing I will add is If you let the car set overnight less fuel will be lost when you disconnect the fuel hoses at the sender.

Here is the post
http://www.bimmernut.com/forum/showthread.php?t=41680

[bubba966]

Yes the sending unit can be removed, opened and cleaned. I did this a month ago to my sons 735i. There is a posting on this sight. On thing I will add is If you let the car set overnight less fuel will be lost when you disconnect the fuel hoses at the sender.

Here is the post
http://www.bimmernut.com/forum/showthread.php?t=41680

Did cleaning it solve any funny readings? What'd you clean it with?

[bubba966]

So, finally got around to changing fuel pump and the sender units, not from my 525 as the pump differs but from a 95 540 @ the salvage yard.. Now the gauge works like it should and as a bonus the obc now reads below 8 liters on obc code 7, got a reading of 4.4 liters after installing the new units (not on code 6 tho, that still reads 8 liters) Never had it do that before! :)

Another thing that I found was that my old pump wasn´t seated properly lacking about ½ inch on the right side looking into the tank, so be thorough and seat it really well by pushing a bit hard when you have to reinstall the pump! ;)

Changing the sender fixed the goofy gauge readings then. That's good to know.

Was going to swap senders from my good working one in my M-Sport to her questionable one from her 525iT. But after we pulled off the access hatch to her sender it looked like we should wait and get new gaskets before we pulled the senders out and swapped them.

[Kibokojoe]

Yes it got rid of some of the erratic readings but it still has problems once you get down to 1/4 tank. I think I need to replace the capacitors. Where can I find information on capacitor replacement.

I used cotton balls and electronic contact cleaner

[Bo525i]

Capacitor fixes: http://www.bmwe34.net/Wiki/tiki-index.php?page=Dashboard+capacitors

[tim eh?]

Changing the sender fixed the goofy gauge readings then. That's good to know.


+1 - thanks for posting this.