E34 economy/instant MPG gauge problem

[General984]

My economy gauge bounces up all the way to +30 liters the moment I start the car.
When I start moving it drops to 0 and stays there,no metter how much I depress the gas pedal.
Can someone tell me how this gauge works? What connections do I need to check?
I already tried replacing the cluster,but the problem remained.
644885

[shogun]

when you start the car and do not move, then it will be on your EURO model maximum reading, because it should show liters/100km, but as you do not move, it shows max. reading. Copied from the E36 owners manual:
The energy control indicates the current fuel consumption in mpg (in liters per 100 km on Canadian + EURO vehicles). When the vehicle is stationary, the needle returns to zero (maximum reading on Canadian + EURO models).

But when you start moving, it should start showing the consumption. I would check the speed sensor on the final drive/differential, maybe that does not send a clear signal to the cluster, where the signal is processed http://www.bmwe34.net/E34main/Maintenance/Electrical/speed_sensor.htm

[General984]

Speed gauge works completely fine,so I assume sensor is working..Anything else?

[shogun]

check on the cluster if the the connector X271 grey has good contact, pin 8 and 10 are the speed signal http://www.e32-schrauber.de/bmw/daten/schaltplaene/kombi/steckerbelegung-x271.pdf

[General984]

Can I test that with test light?

[shogun]

Maybe a electr. expert can tell you, what kind of signal you receive there respect. can measure.

[Honolulu]

Rotate the wheel slowly and use a multimeter set to volts on one wire at a time and ground. The sensor sends a pulse that the multimeter will detect. An analog meter is more useful in this situation (shows pulses better) than a digital multimeter.

[IvakaG]

Hello, I have been having absolutely the same problem since I bought my car. Were you able to resolve somehow it or you gave up? ��

[Nowar0060]

İ have the same problem and i can't figure it Out
Did you fix it by any chance

[shogun]

did you check the speed sensor on the diff? http://www.bmwe34.net/E34main/Maintenance/Electrical/speed_sensor.htm
the economy control display is actuated by a microprocessor. The road speed signal from the rear axle reed contact and the injection signal TI serve as basic information for this purpose. The TI signal comes from the DME control unit, is processed in the instrument cluster and delivered to the EC. In addition, at idle speed (car stopped) the indicator will dis-appear under a mask and no longer point to maximum fuel consumption as in the past.
Excerpt from instrument cluster/check control training reference book, information status 01/1989