Gas Gauge Acting Funky....

[lespaul]

I've been noticing that my gas gauge will read 3/4 tank, then 1/2 tank, then 3/4 of a tank..etc.. Is this a typical finicky issue with e30's, or specifically m42's? Is there a fix?

[bimmer_E30]

mine does that....

[lespaul]

So what do you give the benefit of the doubt to, the higher reading or the lower? :?

mine does that....

[Nicademus]

Mine does it too but if I just poke at it a bit it goes back to normal..........or gets stuck on full which is helpful..

[dkbmxer002]

mine does it all the time usually only at lower levels, i just tap it or sometimes punch the shit out of it.

[e34john]

Mine is stuck on full about 98% of the time. Then sometimes on startup it will go to the right or what I think is the right place and then bounce back to full after I start driving.
Haven't bothered fixing it but I did run out of gas once in the year and a half of daily driving. Someone took the car without me knowing and it threw off my refueling schedule

[lespaul]

Well, what's scary is my odometer isn't working.. So I'm basically driving in the dark. Any known solution to this? Maybe fix my odometer. Also the one of the fun things about the m42 is to see what kind of mileage I'm getting..

[e34john]

hahah me too, but I have a pretty routine route that I drive. It could be the SI board but that strange because all my other gauges work. I checked to see if the cluster was grounded properly and it looks to me, I didn't have my dad's test light to check. Other thing I thought about was the fuel sender unit but due to price and that theres two of them I decided against replacements for now.

[Ruffian]

Problem can sometimes be a faulty sender in the tank. Unfortunately for these, the technology is fragile. There is a small thread wire inside the sender(about 50 guage wire) and when this breaks, all kinds of readings are sent to the dash. I tried to repair mine with some different bare wire, but I think I used too thick of wire and the resistance reading was off, so I got a full tank all the time.

To check the sender, remove it from the tank, then undo the small nut on the bottom. The cannister will slide off and reveal the thin wire inside the unit.

[Das Boots]

The M Technic II would fluctuate once in a while when the needle is just below 1/2 and would be really be sick on 1/4 tank. I figure it is the sending usnit or level indicator. But I just let it go. It tells me it is time to fill up......

[george graves]

There is a small brass nut on the back of the cluster - it has a way of backing off a bit and loosing ground to the gauge. Tighten it back up.

[lespaul]

Stupid question, but I just got the car. How do I get to the back of the cluster? Is it a big job? I'm not too mechanically inclined.

There is a small brass nut on the back of the cluster - it has a way of backing off a bit and loosing ground to the gauge. Tighten it back up.

[george graves]

You'll need a 22mm socket on an extention to remove the wheel. A Phillips to remove trim. It's not fun, and you'll drop/loose screws all over the place. Do you have an e30 friend that can help?

[lespaul]

hmmmmmmm.. I think so actually, or the mechanic down the road, he's pretty quick. thanks so much for the info.

You'll need a 22mm socket on an extention to remove the wheel. A Phillips to remove trim. It's not fun, and you'll drop/loose screws all over the place. Do you have an e30 friend that can help?

[Rogan]

takes about 5 minutes to take it out, the first time.

1. drop the knee-trim cover from the lower dash
2. reach up behind the black trim (just below the cluster, that goes across, above the steering column).
2a. there are two round finger-nuts, about the diameter of a dime, about 1/4" thick.. the black trim in #2 has a stud on each side of the column, pointing toward the firewall. remove these aluminum nuts, then pop the black trim out.
3. 4 black screws, two silvers.. remove them to take out the cluster surround. two black screws above cluster recess area, two black ones/two silvers on the lower face of the cluster, behind the trim panel removed in 2a.
4. Once that is out, there are two screws that hold the top of the cluster in.. almost vertical. located at about 11-1 positions, on A-shaped brackets. take them out.
5. Tricky part - but dont be scared.. get ahold of those top a-shaped brackets, and rotate the cluster downward.. kinda like you're taking the top of the cluster, and folding it down to the top of the steering column..it'll be tight, but it will plop down.. 6.3-4 connectors on the back of the cluster: Yellow, Blue, White, and maybe one or two smaller ones. If there's one in the green plastic housing ont he back of the speedo, notate where it plugs in; it's for the O2S.
6a. the three colored plugs have a black 'lock' on each. just pupp the black piece straight up, about 1/2 inch, then the plug will come out.. start right to left (blue, then yellow, then white) and rotate the temp gauge side out, first, bringing it through the steering wheel (have steering wheel with largest opening at the top, like put the wheels straight.)..
7. Once it's out, you'll see a small M3 or M4 size brass stud sticking out of the back of the cluster, on each side (one behind fuel gauge, one behind temp gauge).. ensure they are tight.

I just fixed my gauge last night. Mine would show 1/2 tank, and reserve light on.. so i swapped the sender; no change. So I swapped the gas gauge from another cluster, and now I'm good to go..

If you need to try and swap the actual gauge in the cluster, remove that brass nut mentioned earlier, and about 8 hex-headed phillips screws from the back of the cluster's perimeter.. the two halves will pop apart. then firmly grap the fuel gauge assembly piece, and work it off the board. It's only two slip-fit prongs and the threaded stud..

Assemble in reverse order.


EDIT:

the sender is held in by 4 8mm nuts, under the rear seat. unplug the sender plug from it (largest of the two), remove the 4-8mm nuts and washers.. then GENTLY lift the float assembly straight up and out. have a rag or small bucket handy in the floor, so you can use it to get the float out of the car w/o getting fuel everywhere..

you can test the float with a DVOM if you dont want to pull it apart, but you'll still need it out of the car, at least..

(the above float removal is for early E30 with transfer pump. non-xfer pump cars are a little different.)