Z3 Fuel Gauge Fixes: Stuck Low Fuel & Wacky Gauge

[Monolith]

I’ve encountered two different types of fuel gauge issues that required different fixes.


Problem #1 (aka "Stuck Low Fuel"):

Cause – Gas station attendant “topped off” the tank (NJ issue).

Symptom - Gauge was stuck on low fuel level with low fuel light ON.

Fix 1 – Unhook battery to reset (turns off light and fuel registers correct level)



Problem #2 (aka “Wacky Gauge”):

Cause – Unknown.

Symptom – Gauge erratically swings from full to empty at random times. Seems to mostly occur when tank is full. Tapping on dash near the fuel gauge sometimes makes the gauge correct itself.

Fix 2 – Make a better electrical connection between the front of the gauge cluster and the rear of the gauge cluster for the fuel gauge.



Some background info – my car was taken to the dealer by the previous owner who had a technician chase down the problem. He started from the fuel sending unit and traced it to the gauge cluster. I believe at this point the previous owner was told that there was some type of short in the cluster and it would require a new cluster ($700). The previous owner declined. I bought a second cluster to practice on and then implemented the following repairs on the car’s cluster.

In addition to the following, I also used contact cleaner (CRC QD Contact Cleaner – available at Home Depot in the electrical department) on all of the back connectors and worked them on and off to ensure everything up to that point was getting a good electrical connection.

I’ve not had a problem for over a week now after the following fix, but I cannot guarantee it will fix your particular gauge issue.

Note: I also use Techron in my fuel in addition to the fixes.



Cluster must be removed. Here are a few cluster removal links:

http://www.unitedbimmer.com/forums/e...done-pics.html
http://rides.webshots.com/album/219881572pOuUKG
http://www.brazeauracing.com/instrcluster.htm
http://forums.bimmerforums.com/forum...d.php?t=337504




The fuel sender wires connect to the back of the cluster at the black connector on the left side.





The following picture shows the fuel sender wires that plug into the black connector. Only 3 pins are used (pins 1, 3 and 4) of the black connector.





Separate the front and back of the cluster by removing the screws. You’ll find three pins on the left side of the front part of the cluster that go to the fuel gauge as circled in the picture.





Below is an enlarged picture of the three fuel gauge pins. These pins are not making a tight connection with the rear part of the cluster causing the electrical connection to be faulty. I cleaned the pins with Caig DeOxit (available at Radio Shack).





For those that don’t wish to pursue the mechanical approach that follows, you can probably obtain good fix results by just coating the three pins with conductive grease (not dielectric grease). This should give a sufficient electrical contact improvement to fix the faulty contacts. To be doubly sure, use the conductive grease and the mechanical fix. I only implemented the mechanical fix because I did not have the conductive grease available at the time.

http://www.mouser.com/Search/Refine....tt=590-846-80G





On the back part of the cluster, locate the receiving section for the fuel gauge pins as circled in the picture.





Inside each of the pin holes, there is a portion that makes contact with the left and right side of a pin. Each contact can be bent slightly by inserting a thin edged device under the contact at the point shown by the red line and the yellow arrows.





In the picture below, a thin blade of a knife is used to slightly bend (influence) a contact towards the center of the hole. This should be done gently for both the right and left contacts for each of the three pins. If you don’t feel comfortable in doing this step, just using the conductive grease on the pins will most likely fix the gauge. If the contacts are broken during this process, it will require removing the circuit board from the back of the cluster which requires plastic melting and soldering. I highly recommend not getting too carried away with bending the contacts. You just need enough pressure on the pins to eliminate car and road vibrations from breaking electrical contact.





The final result is a rock steady fuel gauge.

Good luck!

[JoshS]

Funny. There was a TSB back in '99 (if memory serves) for the 2nd issue ... it required a new fuel gauge sender (in the fuel tank).

The first issue sounds like one, about the same time, that was fixed with a software reflash.

[IslandS62]

Interesting! Good thread. I had the same problems in my 99 and I repaired it by replacing the fuel pump and sender in the tank. Its about a 90 minute job removing the seat and such but it cured my problem and it never recurred. If your method also works then I guess it a bit of "pick your poison" on which to use.

However if the problem is indeed a loose gauge connection, then I can't see how the accepted fix of sender replacement works as a permanent fix, and in my case, it was.

*edit* Nevermind I see the problem in your case was already traced to the cluster.

[Jeremy]

Great thread and very thorough. Thanks for posting!

[organic///M]

You should post a link to this in the "Z3 FAQ + Write-ups, how-to's and DIY links" thread: http://forums.bimmerforums.com/forum...t=56864&page=7

[Monolith]

Funny. There was a TSB back in '99 (if memory serves) for the 2nd issue ... it required a new fuel gauge sender (in the fuel tank).

The first issue sounds like one, about the same time, that was fixed with a software reflash.

I've not ran across the software reflash fix yet. I'll do some more research on that. Sounds like a good fix only if the car is still under warranty.

You should post a link to this in the "Z3 FAQ + Write-ups, how-to's and DIY links" thread: http://forums.bimmerforums.com/forum...t=56864&page=7

Done!

[cngizbleevng]

Thanks for that info! This is the kind of helpful info that makes this board so great!

Question about the Carbon Conductive Grease... I have an ipod connection that occasionally gets static and the sound quality suffers. If I unplug and replug that connection, the sound improves. Would this grease be good to use at that connection?

[Monolith]

Thanks for that info! This is the kind of helpful info that makes this board so great!

Question about the Carbon Conductive Grease... I have an ipod connection that occasionally gets static and the sound quality suffers. If I unplug and replug that connection, the sound improves. Would this grease be good to use at that connection?

The conductive grease is rather heavy for that type of use.

I'm assuming you're referring to the bottom of the iPod connector? For that, I would try the CRC electrical cleaner first (leaves no residue) - spray both connections and then plug and unplug it a few times. If that doesn't help, try cleaning the contacts with DeOxit (and other Caig products - DeOxit and then ProGold, etc.).

If you're referring to a microphone style connector for the front of the radio, I wouldn't use the grease on that because it could possibly cause a short between the plug (stereo) contacts.

[doddi1]

this may be a dumb question, but if i unplug the battery, will it reset something i wouldn´t want reseting ?

[Monolith]

this may be a dumb question, but if i unplug the battery, will it reset something i wouldn´t want reseting ?

You'll lose your trip info and clock at a minimum.

[doddi1]

You'll lose your trip info and clock at a minimum.

thanks, i´ll go try this tomorrow

[JoeZ]

[B]I've not ran across the software reflash fix yet. I'll do some more research on that.

I don't think its a sw issue as my car shows same symptoms from time to time.

[knievil]

OK, I have been living with this problem for a while.
I have read about the wacky guage and was contemplating replacing the fuel sender.
My problem is not a jumpy or wacky gauge but rather the fuel is always low and fuel light is on. I have pulled all the fuses as outlined in IslandS62 thread
http://forums.bimmerforums.com/forum...l+guage&page=2

But if recurs immediately.
I just came across this thread.

A few questions:
1) Does anyone else have the low fuel problem?
2) Does the battery disconnect work?
3) Is there a software reflash fix?
4) Is there another fix someone knows of?
5) Does replacing the fuel sender work?

I would have thought that pulling the right fuses would be equivalent to a battery disonnect.
I appreciate anyone's experience on this. Thanks in advance....


****EDIT****
I just found and have attached a pdf version of the TIS regarding connectors and indicator malfunction. Page 3 is interesting in that it may not relate to a faulty sender but rather a connector / conductance issue as outlined by the OP.This may also explain why replacing the sender may result in failure once again down the track. Stabilant 22A is recommended (quick search showed it at $100 for a 15ml bottle)!
Still wondering whether a battery disconnect will work to save me the hassle....

[Robstah]

I am pretty sure it's still the fuel sender that's the problem. I have had both symptoms happen to me, and that's when I forced in the extra 15 cents worth to complete a dollar on the pump. I quit doing that and I have yet to have that issue since.

Doesn't our fuel pump/level sender sit kinda sideways anyway? I'd say that would be part of the problem. I've never had this issue on my 325 mainly because the the level senders and pump sit straight down into the tank. Even though I have yet to check it out, the flotation device at the end of the sender might be getting stuck on something causing the no read symptom and then when the tank goes down and the car feels jolts from the road, it breaks free and can read properly again.

We do appreciate your write up and if that solves the issue, then by all means, it should be mentioned as a possible fix. I just don't see that many people dealing with the connectors to the cluster outside of their factory install or why they would become loose.

[knievil]

I am pretty sure it's still the fuel sender that's the problem..... I just don't see that many people dealing with the connectors to the cluster outside of their factory install or why they would become loose.

I think you're right. More research revealed this bulletin. Seems I need to order one.

Can anyone confirm that the M and non-M version are different?
It seems they have a different part number.

M = p/n 16 14 2 228 037
Non M = p/n: 16 14 6 756 323

[CiscoKidZ3]

I just topped off this past Friday and now my fuel gage does not register full. I have a 98 Z3 Roadie with 23,500 mi on it. Never had this problem before. So the question is:

1. Do I disconnect the battery and see if that fixes it?

Thanks,

[fmcfad01]

Best way to fix the problem is drive some miles, use some fuel, and then the gauge starts working again with zero time, money or effort spent on your own behalf.

[PbFut]

If it is the sender, it is often just dirty. Techron often fixes the issue.

[wazzuFreddo]

Funny thing about my car, I put Technon in and got the funny fuel gague. It went away after a couple fillups.

[Z-Thrizzle]

Looks like I have a similar problem. Though it may be tied to my cluster since my speedometer is acting up too.
Note:
fuel injectors are new
fuel filter replaced 15k ago
use techron like 3 times a year
diff cover was recently removed to replace bushing, maybe speed sensor was damaged.

(click to see video of issues)

[PbFut]

Looks like I have a similar problem. Though it may be tied to my cluster since my speedometer is acting up too.
Note:
fuel injectors are new
fuel filter replaced 15k ago
use techron like 3 times a year
diff cover was recently removed to replace bushing, maybe speed sensor was damaged.

(click to see video of issues)

What brand fuel do you use?

[rboehl]

I had this problem with a 97 Z3 2.8 and it was the sending unit but I can see it being the connections on the cluster for some.

[Z-Thrizzle]

What brand fuel do you use?

For the past year I've mainly been getting gas at BJ's 93octane. I don't believe I had a problem with the gauge until after the SC install 2 months ago.
The car sat at a 45 deg angle with jack stands in the front about 2 months. This was for doing maintenance and the SC install. Could this have affected the sender?

How difficult is it to replace the sender unit?

[gmushial]

If it is the sender, it is often just dirty. Techron often fixes the issue.

I ran into similar a year ago: fuel gauge would read as always for the top 3/4 of the tank, but then wouldn't drop below that. At first I thought I was getting incredible mileage, until after 80 miles it dawned on me that it wasn't possible if the fuel gauge was working correctly... did a quick trip into the next gas station, and ended up putting in 12+ gallons, ie, it was getting down to nothing. To me since the gauge worked in the top 3/4s of the range, it was a sender problem. And given the cost of replacing the pump/sender, decided to first chemically treat it, and then if that didn't work, mechanically attack it, ie, pull and try to fix anything that was obviously mechanically damaged/wrong/broken... and finally, if neither worked, then replace. Turns out that the first approach did it.... someone in another thread, related, but not the same problem had had good luck with SeaFoam - something that I looked down my nose at... but given the costs involved, gave it a try: filled the tank and dumped a can in. The test was what was going to happen 200 miles later - and the $64k question was answered: the gauge went down through the old sticking point. My guess is that there was some buildup that had interfered with the sender. After the fact threw in a 2nd can just to make sure whatever was gumming up the works was potentially fully gone. Bottom line: haven't had the problem since. After posting the experience, RandyW suggested that one could make their own SeaFoam much more cheaply - and given his track record, I'm sure he is right... but even short of that, a low-buck solution to a potentially otherwise high-buck problem. Don't know if it'll work for anyone else... but might be worth a try.

[Muzz258]

Hi

Had a fuel gauge that went to 1/2 then dropped to empty. The computer's l/100km was telling the truth, tip meter and gas up receipts confirmed that it was accurate and that I was only using 1/2 a tank. So it was not the gauge cluster.

Looked up the operation of the sender unit and it was resistance based. Zero ohms for empty and higher resistance for part tanks to full tank.

Rather than cut the carpet and replace the sender I decided to use almost all of the tank a couple of times to see if there was some gunk shorting out the bottom of the sender resistance track. 6 tanks later and the sender is working correctly for 45 of the 52 litre tank. Now to put a reserve tank of fuel in the trunk and run the tank out a few time to complete the resistance track clean up.

hope this helps others with similar problems.

Cheers

Muzz