Fuel gauge inop - Solved

[snaponbob]

Working on a friend's rather "compromised" M3. Among the laundry list of issues is a completely dead fuel gauge. The needle does not move and the red light is NOT on. Just dead.

Thoughts?

[samy01]

i don't know exactly how the gauge bahaves when one or both of the sensors is broken, but when i disconnected one of them, the needle went towards empty, i don't remember if the light came on. maybe it helps to visually check the connections or maybe do a resistance measurement of the fuel level sensors to see if they're good or not.

[JDStrickland]

My car would show E, then remain there after the fill up. After some random period, the needle would jump to the then-current level, and then fall as expected until it got to E, and repeat. I always filled the tank, so I was observing E at a time when I should have seen F. The problem that I fixed was dirty sweeps on the fuel level sending units. I pulled the sending units out -- the right side of the car includes the fuel pump and sending unit together -- and cleaned the contact sweeps. I used a course business card for texture and some contact cleaner for the chemical component.

- - - Updated - - -

I do not recall the condition of the Low Fuel Indicator light. The needle stayed on E with a full tank of gas, then it would eventually jump to the current fuel load and fall correctly to E. I set the odometer to zero on the fill up, and the needle got back to E after 300-ish miles at 80-ish MPH.

[shogun]

apparently it is unfortunately often that the wire(s) of the fuel gauge sender unit inside the fuel tank get's lose. Resolder or replace the old wire and the problem should be solved. https://www.bimmerforums.com/forum/s...stays-at-empty
In post # 13 there is a SI with a data on resistance to measure https://www.bimmerforums.com/forum/s...mp-Wacky-Gauge

[snaponbob]

Again, the gauge is dead and the RED LIGHT DOES NOT COME ON.

I will rephase this and say that the gas gauge is inactive -- in every aspect.

That said, I have not had the cluster out to see if the low fuel light is burned out.

[shogun]

Here is the E36 cluster plug pinout from a German forum with my translation

weißer Stecker/white plug:

1 - Kontrolleuchte Fernlicht/control light high beam
2 - Instrumentenbeleuchtung (Klemme 58g) / cluster ilumination, terminal 58g
3 - Kontrolleuchte Blinker rechts /control light turn signal right
4 - Kontrolleuchte Blinker links / control signal turn signal left
5 - Warnleuchte elektr. Getriebesteuerung /warning light electric gear/transmission control
6 - nicht belegt/ not used
7 - nicht belegt/ not used
8 - Warnleuchte DDE / warning light DDE
9 - Vorglühkontrolle/preglowing control light (diesel)
10 - Warnlampe Überrollschutz/warning light roll over protection cabrio
11 - Diagnose RxD
12 - Diagnose TxD
13 - Öltemperatur/oil temperature
14 - Warnleuchte Airbag/warning light airbag
15 - Klemme R, z.T. nicht belegt/terminal R, partly not used
16 - Motorkontrolleuchte (Check Engine)/ check engine light
17 - Warnleuchte Handbremse/warning light parking brake
18 - Warnleuchte Bremsflüssigkeit/warning light brake fluid
19 - Warnleuchte Bremsbelagverschleiß/warning light brake pads
20 - Drehzahlsignal/ROM signal
21 - Kraftstoffverbrauchssignal/fuel consumption signal
22 - Klemme 30/terminal 30
23 - Klemme 15 (Spannung für Kontrolleuchten)/terminal 15, power for control lights
24 - Klemme 31 (Masse für Kombi-Elektronik)/terminal 31, ground for cluster electronics
25 - nicht belegt/ not used
26 - Warnleuchte Katalysator-Übertemperatur/warning light cat overheated

blauer Stecker/blue plug:

1 - Kontrolleuchte Anhängerblinker/control light turn light for trailer
2 - Tacho A-Signal/speed meter A-signal
3 - Klemme 31 (Masse für Kontrolleuchten)/terminal 31, ground for control lights
4 - Klemme 15 (Spannungsversorgung der Kombi-Elektronik)/terminal 15, power supply of cluster electronics
5 - Klemme 15 (Spannungsversorgung Ladekontrolleuchte)/terminal 15, power supply alternator/battery control light
6 - Klemme 61 (Masse Ladekontrolleuchte)/terminal 61, ground battery control light
7 - nicht belegt/ not used
8 - Kontrolleuchte Nebelscheinwerfer/control light foglights
9 - Akustikausgang Warnsignal (zum Gong)/accustics out signal to gong
10 - Ausgang Informationssignal Tankinhalt für Bordcomputer/output signal information tank volume for board computer
11 - Warnleuchte ABS/warning light ABS
12 - Warnleuchte ASC/warning light ASC
13 - nicht belegt/ not used
14 - Warnleuchte Gurtwarner/warning light seat belt
15 - Restet für Serviceintervallanzeige/reset for service interval indicator
16 - Klemme R/terminal R
17 - Kühlmitteltemperatursensor/coolant temperature sensor
18 - Kühlmitteltemperatursensor/coolant temperature sensor
19 - Warnleuchte Öldruck/warning light oil pressure
20 - Fehlerlampe SMG (M3 SMG)/fault light SMG M3
21 - bis 9/96 nicht belegt, ab 9/96 Masse/ up to 9/96 not used, from 9/96 ground
22 - nicht belegt/ not used
23 - nicht belegt/ not used
24 - Ausgang Dimmsignal/Helligkeitssignal/output dimmer signal
25 - nicht belegt/ not used
26 - Warnleuchte Check-Control/warning light check control


schwarzer Stecker/black plug:

1 - Tankgeber/Kraftstoffniveaugeberfuel /tank level sender
2 - nicht belegt/ not used
3 - Tankgeber/Wegsignalgeber (Reedkontakt) Masse Klemme 31b/fuel tank sender/mileage sender reed contact
4 - Eingang Wegsignal TW (Reedkontakt Wegsignalgeber)/in signal mileage TW (reed contact, mileage sender)
5 - Kontrolleuchte Nebelschlußlicht/control light rear fog light
6 - nicht belegt/not used
7 - nicht belegt/not used
8 - nicht belegt/not used
9 - nicht belegt/not used
10 - nicht belegt/not used
11 - nicht belegt/not used
12 - nicht belegt/not used

[jc43089]

The fuel senders are in series so an open circuit at either one and the gauge will read empty. I think they are about 350 ohms each so around 700 ohms total when full because they are in series (those are not exact numbers). Just pop up the rear seat and take the access covers off. Unplug the electrical connector on each sending unit and check the resistance with a multimeter. They will likely not read the same unless the tank is full FYI, the non pump side will be lower if the overall level is closer to empty because of the siphon transfer system. The right side is a combo of the pump and sending unit but the plug I think is different so you will be able to tell which connecter is the pump and which is the sending unit.

[shogun]

Fuel sender ohms left and right and full and empty accdg to SI 16 04 98 are here https://www.bimmerforums.com/forum/s...6#post17792986

[E36328Coupe]

If you have an OBC check range. If range is --- car thinks it is out of fuel, if range is high it may be just the instrument cluster.

[snaponbob]

I appreciate all the input. Assuming the red light is good, the either the meter movement is broken or the gauge is dead. If the sender plugs are unplugged, the gauge will show empty AND the light will be on.

[snaponbob]

Took the cluster out after tapping on the glass and the needle moved to half, then shivered and headed to the E. Pulled the cluster apart, put it back together, and the gauge works. Wonders never end.

[shogun]

That sometimes helps, so some things happened like you unplugged for example the plugs in the back, that could - just as example - have fixed the contact problem of the pins.
I had a similar problem 2 years ago on my 1988 E32 750, used contact enhancer spray and the problem was gone.
I can only recommend to use contact spray and enhancer in all electrical connections on our old cars, work sometimes wonder. BMW has a service info on that:
BMW recommends to use Stabilant 22A Electrical Contact Enhancer,
Features
- Electrical contact enhancer
- Leaves a thin polymer film that is conductive between mating surfaces, but is non-conductive between adjacent pins

- BMW bulletin # SI 610500 Stabilant 22A Electrical Contact Enhancer Model: All BMW
Complaint:
Connectors which carry low current are more likely to form deposits which affect the resistance of the circuit through the plug connector. Depending upon the particular circuit these deposits can cause malfunctions and consequently activate warning lamps and check control indicators.
Remedy:
Part replacement can temporarily stop the problem.If the connector is the problem then without disconnecting the connector measure the resistance of the circuit running through the connector to make sure the connector has a high resistance. A good resistor will have close to 0 ohms resistance. Visually examine the male and female terminals in the connector housing by removing them. Look at the integrity of the wire crimps, and in some male terminals the integrity of the weld of the male pin to the terminal. Then reinstall.With a zero residue electrical contact cleaner liberally spray the male and female connectors, and allow the air to dry. Apply Stabilant 22A to both male and female terminals so they are saturated, and reconnect the connectors while they are still wet. When the Stabilant 22A dries it will leave a thin coating of polymer film which is conductive between mating surfaces, and is non-conductive between adjacent pins. It can also prevent the formation of more harmful deposits.

- When applied to contacts, it provides the connection reliability of a soldered joint without bonding the contacting surfaces together

Areas of use: - Electric ignition system,- Instrument clusters
- Blade fuses, - Bulbs, - Heater and AC controls,- Car stereos and speaker connections,- Sensor connectors,- Electric rear-view mirrors,- Solenoid door and trunk locks and power windows,- Horn circuits,- Tail lights, parking lights and headlights,- Trailer connections,- Door activated switches,- Battery terminals and starter lugs and terminals,- Voltage regulators, alternators and generators,- Diagnostic equipment,

Is available from BMW, Wurth, other makers like De-OxiT, I use a product from Philips, because easiest to get here where I live.

[snaponbob]

ALWAYS good input from Shogun.

May need your input on another gas gauge issue on a 95 M3 clone I am building for a friend. The gauge reads empty and the red light is on. I KNOW there is 5 gallons of gas in it. I have installed a dual pump system to avoid fuel starvation in hard/long right turns on track. I will be rechecking my wiring work. I pulled both pumps (new VDOs) and used a multimeter to confirm that both are working properly. Also, (and maybe unrelated) the temp guage reads straight up when the engine is cold. I unplugged the sensor and the gauge reads cold. May be a bad sensor, or the cluster may be screwed up.

More later. The temp sensor will be replaced, and the fuel pump wiring will be checked.

[shogun]

Besides other things, this wire you have to check, that is for fuel pump sender and often breaks http://s71.photobucket.com/user/shog...ml?sort=4&o=13
There is a DIY on a German forum in case of probs with level sensor, to check this first on the E36

[snaponbob]

I have "swept" the level sensors with an ohm meter. Bothe read correctly. As a matter of fact, I used those same two pieces in M3 for a week with ZERO issues. The problem is apparently NOT the fuel pumps. The installation requires some rewiring, so I will check that. What I would REALLY like to know is the input voltage values at the level sensors should be.

[snaponbob]

Well, seems the C plug was not in place. Done!!!

[E36328Coupe]

C plug?

[snaponbob]

C plug?

There are three plugs in the back of the instrument cluster. A, B, and C. The C is the small, black plug.

[E36328Coupe]

Ah I know them as X16,X17 and whatever

Did the car have an OBC?

[snaponbob]

Ah I know them as X16,X17 and whatever

Did the car have an OBC?

Yup. But currently not functional. Borrowing a known good one to check out the connections.