Fuel Gauge/Economy Gauge & Missing wires?

[Sooty]

Just bought an 88' E plate 320 4dr for a daily runner.
It's no show car, but it's not a total rustbucket & it'll do for me.

When I picked it up, I noted that the fuel gauge, service lights and economy meter were'nt working.

Set to it today by looking at the fuel gauge first.
Put £20's worth in; low level warning went out but gauge still sits on zero.
Earthed out the Bn/Gn on the LH sender & the gauge goes to full.
Earthed out the Bn/Gn on the RH sender & the gauge goes to just over half. Reconnect the RH sender & the gauge stays on zero.
I'm assuming it's the RH sender that's at fault? Anyone care to confirm?

Then took the clocks out to check the small bolt on the back of the cluster.
Removed the blue & white plugs, tilted the cluster fwd but no yellow plug connected. WTF
I've had a damned good look, but for the life of me, I can't find a yellow plug anywhere behind the dash & even though there's evidence of the clocks having been out before, there's no sign of any cut wires.
I've had older models than this one & they've had all three plugs so what's going on here?
Anyone come across this before?

Iain S

[Gwynleym10]

I think the yellow plug is for cruise control. Most UK e30's don't have it

Have you checked the grounding nut (the nut on the back of the fuel guage) this often come loose or dissapears!

Common fault, this should fix your fuel guage and eco meter.

What are the service lights doing? Nothing at all?

It might be the Service Indicator batteries.

If this doesn't work try another set of guages.

[bobgil67]

the yellow plug is for the on board computer.

[Sooty]

Cheers for the quick replies fellas

Just checked the grounding nut & it's tight but the gauge is still at empty and the eco gauge is still at 50+.
Still looking like the RH sender then?

Service lights are showing nada, zilch, nothing, bugger all. I've got an SI board from a 318 so I'll swap the coding plug & try that out (had'nt thought of that .

Car is'nt fitted with an OBC, just an overhead check panel but this is my 6th E30 & the first one I've seen without the yellow plug.
I even had the plug on a no frills, B reg, 316 carb model FFS!

[Sooty]

Good call Gwyn

Just changed the board and all the lights are there.
Think I'll have a go at changing the batteries on the one I've just taken out & see if I can get it working again.

Never know when you'll need a spare do you?

Now I've just got to solve the mystery of the missing yellow plug & sort out the fuel gauge

Iain S

[Brianmoooore]

I'm assuming it's the RH sender that's at fault? Anyone care to confirm?

Iain S

Very likely. If the gauge reads (too high) when you link the two wires together, then definitely.

[Brianmoooore]

I've had older models than this one & they've had all three plugs so

Iain S

Only thing that plugs into the yellow socket is an OBC.
No OBC and the socket should be empty.
Green socket only appears on some cars, and is used for speed sensitive radio and, I think, cruise control.

[Sooty]

Cheers Brian

1/ Defo the RH sender.
2/ Surprised not to find a yellow plug in the loom because I had one on my old carb 316 & that did'nt have an OBC. I assumed it was a std loom behind the dash

Just taken the car for a run to the shop & now the economy gauge is working
Obviously (hindsight is such a wonderful thing ) it's run by the SI board & has got cock-all to do with the fuel gauge reading.

[Jos]

Interestingly I always thought the econo gauge was getting its reading from both the ECU (injector duration and revs) and the speed off the diff sensor. Fuel and speed being measured would give mpg.. but the econo arm still does the same behaviour even when the speedo isn't working :p

Go Figure..