Fuel tank Sender unit

[Bonymaenjack]

I replaced my wiring loom from a donor car, the age of the donor is not known (mine is a 32i 1988 facelift with a 63 litre tank) . I've connected everything up with the exception of the separate sender unit ( 2x brown and yellow trace wires ) the fuel gauge is showing fuel in the tank as half full but now the low fuel warning light has now coming even though it is showing half fuel .I've tried following the wiring diagrams but with little success as to how to reconnect these last two connections. Any advice or help please

[Brianmoooore]

Not quite sure what you've done here, since if any of the level sender wires are left disconnected, the gauge shouldn't move from 'empty'. For what you describe to happen, the left over wires would have to be shorted together, or you've fitted the loom from a 55 litre tank car, which wouldn't have any left over wires in the first place.
Also, the tank sender wires are brown/green, not brown/yellow.
Assuming you've fitted the wrong 55 litre tank loom, the simplest solution is to fit a plug to the LH tank sensor and run the wires from it along the top of the tank, to the fuel pump/RH level sender. Cut the brown/green to the three pin plug on the RH level sender a couple of inches from the plug, solder one of the cut ends to either of the wires from the LH sender, and the other wire from the LH sender to the other cut wire at the RH side. Insulate properly, preferably with heat shrink sleeving, and the job's done.

[Bonymaenjack]

Not quite sure what you've done here, since if any of the level sender wires are left disconnected, the gauge shouldn't move from 'empty'. For what you describe to happen, the left over wires would have to be shorted together, or you've fitted the loom from a 55 litre tank car, which wouldn't have any left over wires in the first place.
Also, the tank sender wires are brown/green, not brown/yellow.
Assuming you've fitted the wrong 55 litre tank loom, the simplest solution is to fit a plug to the LH tank sensor and run the wires from it along the top of the tank, to the fuel pump/RH level sender. Cut the brown/green to the three pin plug on the RH level sender a couple of inches from the plug, solder one of the cut ends to either of the wires from the LH sender, and the other wire from the LH sender to the other cut wire at the RH side. Insulate properly, preferably with heat shrink sleeving, and the job's done.

As per my other post on regarding the Rev and ecometer , I suspect the loom is for a 55 litre tank , the sender unit (located in the nearside of the tank ) is definitely not connected just the two wires which are now just tails. You were correct the colour codes are brown with a green trace , I didn't realise that there were two sender units so hopefully thats one more problem solved

[Brianmoooore]

Check that pin 6 of your ECU plug is a plain black wire and pin 32 is a white/black wire.
There should be continuity between these pins and a plain black wire on pin 7 of the blue instrument cluster plug and a yellow/white wire on pin 11 of the blue plug respectively.

[Bonymaenjack]

Brian , your advice has worked but instead of running an additional wire across the tank I broke into the loom adjacent to the sender unit and joined the wires there . Cheers Keith

[Bonymaenjack]

I've established that the both gauges work by spiking the black signal wire into the blue connector e for the instrument panel , the revs at idle appear to be correct and rise as the accelerator is depressed . The ecometer goes over to the right of the gauge at idle . Is it possible as a worse car case scenario to connect to the - side of the coil and connect straight into the blue connector by passing the ECU ? preferably I would like it wired as original but if theres no issue regarding over loading the signal wire which is a 0.5 gauge as opposed the coil which is significantly bigger .

[Brianmoooore]

Don't connect the tacho to the coil - it (probably) won't like it.
Have a look at the wiring behind the instrument cluster area and below, and see if there's a three pin plug hanging down with the black and white/black wire, and nothing plugged into it.

[Bonymaenjack]

Brian . I've located a 3 pin plug adjacent to the ECU but the colours are as follows :
Red/Blue, Black/white or it could be grey
Purple /grey all 1.0 gauge

Coming out of the Ecu loom is a flat female connector with the following colours
Black . Green & Yellow / White all 1.0 gauge but I can't find an appropriate male connector .The 3 x looms was replaced feeding the instrument cluster but not the ECU loom .I'm also not getting all the readings out of the 13 button OBC which I suspect is connected with this issue.

[Brianmoooore]

Plug you're looking for is connected to the body looms, not the engine loom. The ones you've found are for aircon and auto. transmission.
It was used on early E30s with a rectangular engine loom plug and socket, when increasing engine management sophistication required more pins that the rectangular plug had.
This arrangement seems to have overlapped the introduction of the 20 pin round engine loom plug and socket for a short while.
You could check out the body loom side of your C101 engine loom socket, and see what wires, if any, are connected to pins 8 and 9.