Fuel Gauge

[sadham]

Hi Guys,

I replaced my Fuel gauge nut but the gauge isn't working.

I purchased some M4 brass nuts. They seem much thinner than the one on the Temp gauge. Could the nut size be the reason it doesn't work.

first image is New nut, second image is old nut on Temp gauge.

[Brianmoooore]

Could the nut size be the reason it doesn't work.

No. Find the brown/green wire on the plug and socket under the rear seat cushion on the RH side, and use a short piece of wire to short it to one of the brown wires or to a good body earth, and see what the gauge does with the ignition on.

[sadham]

Firstly, thank you for your patience with me. I am a Noob with pretty much anything car related. Learning as I go along Just so I don't damage anything am I right in thinking from your reply that I just get a piece of wire (expose each end of it only) and put it in with the brown/green wire on the right side of the image below, and put the other end in with the brown wire on the left side?... I will be attempting this tomorrow after work and will update of any changes etc.

[Brianmoooore]

That's basically it. Leave the plug and socket together, and push the wire in by the wires until you make contact with the metal of the pins. Doesn't matter which end you push the wire in.
While you're at it, short a brown to the brown/grey as well, which should light the low fuel lamp.

[sadham]

Will this method fix the fuel gauge always showing as empty or will this be a way of troubleshooting to find out what may be causing the problem? You know oddly enough, it 'seemed' to work before I removed the cluster... only it had no nut on it when I removed it.

[Brianmoooore]

This is a diagnostic test. Depending on the result, it may be followed by another one.

[sadham]

Hi Brian, after inserting the wires and turning the ignition to position 2 the fuel tank shows as full.

[Brianmoooore]

In that case, the problem is with the fuel level sender.
Just inboard of the plug and socket, there is a black inspection cover on the seat pan, held in place by cross head self tapping screws. Remove this and you will see the fuel level sender with a plug connected to it with the other end of the brown/green and brown wires. Pull the plug off and use the piece of wire to short the two wires together here, and confirm that the gauge moves.
Exactly what is under the inspection cover depends on what model and age of E30 you have, although I can see from your last pics. that it has rear drum brakes, so is presumably a small engined saloon.

[sadham]

(see image attached) is this what you meant? The fuel gauge showed an empty tank. wasn't quite sure what you meant so even tried shorting it from the brown/green and brown wires from the white plug on previous image above (both sides one side at a time)

[Brianmoooore]

Three of the wires that pass through the plug and socket under the seat end up at the plug in the pic., so you should be shorting together the brown/green and brown in this three pin plug to confirm that you get the same result as you did at the seat plug. This indicates whether there is a fault in this last section of loom under the car.
Assuming the gauge still goes to full, the sender in the tank is faulty. I see that yours in an early car, using an external fuel pump (in front of the LH rear wheel), rather than in the tank like most E30s, which may make it harder to find a replacement, if this one can't be fixed.
Remove the fuel pipes and twist the assembly anticlockwise, and it will lift out. There is an O ring seal which is usually reusable.
As far as repairing the sender goes, I can't help you, as I can't remember the last time I even saw one of these.

[sadham]

Thank you Brian! Managed to sort it out, it was the sender unit which I took apart and sort of fixed (well it's working for now). Will upload some pics later on to show what I did so it can hopefully benefit others too.

[sadham]

From underneath the back seat on the drivers side I removed the fuel sender unit:

I then opened this up by pushing the clips shown in the following pic and lifting the top part up:


Which revealed this: (I then just straightened out one of the thin wires which was seriously curvy.


Reassembled and put back in the car. Filled the tank gradually just to check it does work accordingly and it does . Credit to Brian for getting me this far.