MPG meter on 320i

[daveyboy20]

Mine just doesnt work at all anyone know what it could be or what to look for? cheers

[e30bmlover]

check your fuses.

[bazza93]

is it just the mpg meter not working ??

[Brianmoooore]

It's unusual for the needle to do absolutely nothing. Which side does it sit?

[daveyboy20]

sits to the left of the guage, all my fuses are ok, the service lights do nothing either dont know if its related?

[Brianmoooore]

If the gauge and the SI lights have never worked while you've had the car, it's time to remove and open up the cluster to see if all the bits are present.
Some of the electronics for the econometer are on the SI printed circuit board.

[daveyboy20]

Hmmm, that sounds very compicated... I assumed the MPG thing worked on some sort of vacuum? i wsa hoping there was a pipe somewhere i could check?

[Brianmoooore]

This isn't some kind of crude vacuum gauge - it's an accurate gauge. It computes the instantaneous fuel consumption by comparing road speed information from the speedo with injector pulse width and engine speed information from the ECU.
The usual failure mode is to lose the road speed information. Needle will swing fully to the left on over run, when the injectors are cut off. (zero fuel being used = infinite MPG). Needle will swing fully to the right at all other times, since fuel is being used, and, since the speed information is missing, the gauge thinks the car isn't moving. (fuel being used and no movement = 0 MPG)

[jcjdavis1]

Hmmm, that sounds very compicated... I assumed the MPG thing worked on some sort of vacuum? i wsa hoping there was a pipe somewhere i could check?

Removing Clocks

Hi It is quite simple I did it!

Cover above drivers pedals off
Take steering wheel off (makes life easier)
Plastic trim below clocks off (two thumb screws either end behind trim)
Remove plastic trim around clocks(screws)
Manoeuvre clocks out (after taking screws out)
Take off plugs at either end
Once clocks out remove all screws (on the back) holding on the front plus coding plug
After you have done that you will see the small screws holding on the different clocks.
When you have it all in bits check your batteries on your SI Board for leakage. HTH Jim

PS Someone might have an easier way,thats how I got my clocks out.

Try a breakers for replacement.

[daveyboy20]

Cheers mate! Strangely enough none of our local breakers ahve any e30's in fact the only beemer i saw was an e36! I thought there'd be a few e30's, ah well, ill have to find some time to check the clocks i think

[MrAsp]

This isn't some kind of crude vacuum gauge - it's an accurate gauge. It computes the instantaneous fuel consumption by comparing road speed information from the speedo with injector pulse width and engine speed information from the ECU.
The usual failure mode is to lose the road speed information. Needle will swing fully to the left on over run, when the injectors are cut off. (zero fuel being used = infinite MPG). Needle will swing fully to the right at all other times, since fuel is being used, and, since the speed information is missing, the gauge thinks the car isn't moving. (fuel being used and no movement = 0 MPG)

Useful informations!

Let me ask you a question: my speedo often doesn't work (I was thinking about a wiring problem, I will check), but my MPG doesn't work even when the speedo does!
Have you any suggestion?

If this can help, my SI board batteries were faulty: I have replaced them and now the Service intervall lights are working properly, but speedo and MPG are still in previous conditions.

The car is a '84 320i


Thanks, and sorry for my English!

[Brianmoooore]

The most common speedo problem on E30s is an internal break in the wiring to the diff sensor, within a few inches of the sensor. The vibrations from the diff 'work harden' the copper wire over time and make it brittle.
The last 300mm or so of cable to the diff should be replaced, complete with plug, for a permanent cure.
Second most common speedo fault is 'dry' solder joints on the PCB of the speedo unit itself.

[MrAsp]

The most common speedo problem on E30s is an internal break in the wiring to the diff sensor, within a few inches of the sensor. The vibrations from the diff 'work harden' the copper wire over time and make it brittle.
The last 300mm or so of cable to the diff should be replaced, complete with plug, for a permanent cure.
Second most common speedo fault is 'dry' solder joints on the PCB of the speedo unit itself.

Thanks!
I've already check the solder joints on the PCB: they seems to be ok.
Next step is to check and replace the wiring!:)

What about the MPG gauge? It doesn't work even when the speedo does...