Fuel gauge and range shows random values

[curakpico]

Hello,
I already checked topics about this problem but It doesnt help to me so:

Problem:
When I fill up for example 20 liters of petrol to almost empty tank and put ignition on,
fuel gauge shows 0 liters and range goes from 0 to 195 km. While driving, gauge goes to 40 liters... than to 10 liters..
simply said, it shows random values and "reserve light" is also randomly turning on and off (doesnt matter if gauge is showing 40 or 0 liters).
Range is more accurate but also not working correctly.. For example, those 20 liters and 195 km range on display, after 10 kilometers of driving it shows 70... after next 10 kilometers 120... but when tank contains few last liters o petrol, range is going nicely for example from 60 to 0 very accurately.

What I have done:
I cleaned float and filament wires according to this instructions: http://www.fileoffset.com/bmw/e34_sender_unit.php

497468

Rezistivity is correct after measurement.

After this I took out dashboard gauges (I dont know correct word for this piece of car )
And I heated circuits on PBC by heat gun to avoid possible cold-link.

497469

Doesnt help... So I guess, there will be another cold-link in some socket or wires/cables.

Can anyone give me some hint, where could be a problem? Are there any another sockets? Or familiar knows places, where wires, cables or connections could be damaged or interrupted? Or my opinion is wrong and problem is elsewhere?

[cochise325]

I would be tempted to look at the fuel sender in the fuel tank. There is a float on the sender and you might look to see if it is getting hung up on hoses and wires. Was the fuel pump changed recently?

[curakpico]

Did you read, what I wrote and what I have done? :) Pump wasnt changed... And what has pump related with fuel sender unit? Its connected by hoses and wires...

[curakpico]

??

[ndbag]

Interesting. I read those instructions a while back and have been thinking of fiddling with the sender unit on my car. (Just a resolution for now... I haven't done anything about it yet).

You obviously know what you are doing here, and I can see why you are a bit lost as to possible further solutions. If the sender and the fuel gauge are in good shape, perhaps the problem is somewhere in the wiring between the two? I'm not sure what the best way to diagnose that might be. You could try getting a second (used) sender unit and/or gauge panel and see if changing those produces any noticeable differences/results, perhaps? ^__^;;;

[ZenitramNaes]

I've been having a similar problem. Gas gauge just show reliable fuel level once it's below half of a tank, the light goes on and off randomly as well. I've run out of gas twice now. I've replaced the fuel gauge, and sender unit. I've also put in new capacitors in the dash but I'm wondering if I replaced the correct ones relating to the fuel gauge. SOMETIMES when I hit the dash, the gauge will correct itself, which leads me to believe that it's in fact something relating to the dash. I'm going to dig around a bit more. Idk, just my 2 cents.

EDIT:
Writing that made me realize I should go and try to get to the bottom of it. I pulled out the fuel sender and took it apart. As I moved the floater up and down I could see my gauge going up and down. When I placed the floater all the way down against the contacts, the light came on. So I think this prove that my problem is in the dash. Maybe you could try the same to try to pinpoint your problem?

Nvm, I see that you already cleaned the contacts of the fuel sender.

[curakpico]

I pulled out the fuel sender and took it apart. As I moved the floater up and down I could see my gauge going up and down. When I placed the floater all the way down against the contacts, the light came on. So I think this prove that my problem is in the dash. Maybe you could try the same to try to pinpoint your problem?

I tryed this... NDBAG your opinion might be correct.. I will take dashboard out and I will check all wires and plugs between BC and gauges.

[ndbag]

Good luck! I'd be interested to read more about those tests. How you went about it and what the results were. ^__^

[ross1]

Did you read, what I wrote and what I have done? :) Pump wasnt changed... And what has pump related with fuel sender unit? Its connected by hoses and wires...
Maybe this didn't fix a faulty gauge sender. I suspect a new one will cure this.