fuel gauge misinformation

[steve in reno]

My fuel gauge will read empty and refill will only accept 10-11 gallons to top off. Gauge reads well until fuel level goes below approx 1/2 when it becomes jerky and fluctuates.
Car sat for several years during money depression and as school times required.
"T" light worked but hasn't been seen for a long time. I don't trust waiting that long. Would like to use on longer trips but need to remedy this problem first.
There was a discussion about new ""O" rings availaility thru non-bmw sources for opening up tank to remedy problem. Would like to source parts BEFORE I attempt repair.
I am also going to have my radiator increased to a 3 row, and at the same time would like to add a 7 blade fan to the clutch. Need part number or does anyone have one available?
thanks
steve in reno

 

[andrey]

the level sender is a float with a wire, in a tube. it works by varying the resistance (ie: the level of the float correlates to a resistance). When they sit for a long time, they tend to get stuck. sometimes stuff builds up on them and the float won't go past a point. you should very carefully remove and inspect the sender and make sure that the float travels all they way and that the wires and still there.

to take the thing out, get two flat head screwdrivers and make an X pattern, use them on the lip of the sender body to turn it counter clockwise a little. then carefully turn it a little by hand and gently lift it straight out. undo the nut on the very bottom of the tube (in the filter) to take the sleeve off.

there's an O-ring for the sender and BMW has them for probably next to nothing. you can just measure the diameter and buy a generic one too. It's not a big deal, you can always take it out again and put a new O ring on as it's not at all hard to get to.

the fan and fan clutch are from the E28 and E23, you can get them at the junkyard. there are some issues, like you may or may not need some spacers, etc. overall it's not a big deal.

 

[Honolulu]

fuel sender o-rings

are just o-rings; take the sender with you to the bearing shop (look in the yellow pages) and say "give me something to fit this please". They will most likely respond with something like "here you go sir, that's three bucks and change"

 

[Jellobmw]

Only 10-11 gal to refill? Are you sure you're on empty? Could you have a 2002 gas tank in there?

 

[blumax]

Faulty gas gauge readout

Total gas tank capacity in our Coupes including an approximate 2 Gal reserve is 18.5 US Gals--give or take 1/10--so when the white light starts to flicker on level ground and when sitting still you have about 2 gal to go. Lack of use of the car and having some fuel in the tank for a long dormant period will allow gum to form on the fine wires in the sender unit as mentioned and the float will tend to stick at that point vs its normal range of travel.

Recently I experienced a similar situation with a Bav that was dormant for a long period--IMHO it's questionable that removing the sender unit will correct the condition--maybe try submerging and soaking it in a gallon container of gas with fuel injector cleaner added and in time it may dissolve the "gunk".

My unit was no good as it had been mis-treated at some time in its existence so replacement with new was necessary and they are pricey.

A word to the wise--whether your Coupe is dormant or being driven--keep your gas tank full at all times to prevent 1) internal condensation of the tank--that leads to rusting from the inside out 2) prevents repeat of what you are now experiencing 3) there are other good reasons but my short term memory is impaired--not azsheimers--maybe just halfheimers

Good luck