e30 fuel gauge going mental?

[djhanks]

Right; Just brought an e30 the other day so i don't know much about them or problem wise.
The fuel gauge seems to have a mind of its own and i cant tell how much fuel Ive got in her.
Is this a common problem or?...

[Brianmoooore]

There are three common problems, but I've no idea which without a bit more detail, such as a bit more info. on what actually happens, and what age and model of E30 you have.

[Grrrmachine]

http://www.e30zone.net/e30zonewiki/inde ... Fuel_Gauge

[djhanks]

It's a 1988 (E reg) 318i with a 325 engine conversion.
2 door coupé.
It'll give incorrect reading soon as it starts, then occasionally it'll read full and then all of a sudden it'll read empty or just above the red.

[e30topless]

did you change the coding plug or clocks to the 325i one's ? or was it done during the conversion ?

[djhanks]

I have no idea as I brought the car like it.
The rev gauge doesn't work either if that's any use to you?

[Morat]

Doesn't work as in doesn't move, or doesn't work as in totally inaccurate?

[Brianmoooore]

The rev. counter not working, assuming it worked immediately after the conversion, is probably as a result of failed batteries on the SI circuit board inside the instrument cluster. Needs sorting if it is, before they leak and do damage.
Your description of the problem sounds like it all may be caused by a small brass nut on the back of the instrument cluster case, which has a habit of working loose. This will be the problem if the gauge ever gives a reading higher than what is actually tank, bearing in mind what I've written further down this post about matching tank and gauge.
The 'coding' plug on the cluster only affects the accuracy of the rev. counter, although the rev. counter wouldn't work at all if it was missing completely. It doesn't affect the fuel gauge in any way.
If the whole instrument cluster has been changed for a 325 one, then you will have the wrong fuel gauge for your fuel tank. The effect would be that the gauge would read half when the tank is empty, rising to read full when the tank is actually full.

[djhanks]

The rev counter doesn't work at all.
Ooh ok then well I'll ask the previous owner if he knows weather there 325 or 318 clocks in it.
Well I usually get in it in a morning and its a full tank (bear in mind I park overnight on a slope).
Then I'll be driving and it'll decrease rapidly and then shoot back up to over half a tank and then continue to do that and it'll occasionally settle down and then won't move for ages.
I'll have a look at this brass nut but of its not that then it's the senders in the fuel tank that are faulty?

[Brianmoooore]

but of its not that then it's the senders in the fuel tank that are faulty?

Very probably. There's only one on your car, and it's part of the fuel pump assembly.
Lift up the rear seat cushion, unscrew the screws that hold the oval black plate on the RH side in place, and you will be looking at the top of the assembly. The level sensor is the three pin plug, and is held in place by four small nuts and washers. Remove these, including the washers, and lift the sensor straight upwards and out.
It's a good idea to have a container handy, as it will leak fuel from a small hole in the bottom.
These can fail on their own, but often you will find the can is dented , where some previous muppet has tried to remove the fuel pump without removing the sender first.

[djhanks]

Ok thank you for that I'll have a go at this 1st thing in the morning and will be getting back to you with the outcome