Fuel Gauge

[Stuarted]

My fuel gauge had been very optimistic - i.e., dropped very slowly to half-full and then stayed there as I used the rest of the fuel.

Now shows full all the time. Either a miracle / my prayers answered, or brilliant economy driving skills be me, or the gauge is buggered.

Sady I suspect the third possibility is most likely.

Does anyone know

- is this likely to be the sender, or the gauge, or a wiring problem?
- how to check, please?
- is this a common problem?
- is it easy to fix?
- how does the system work? Is it a simple rheostat on the sender (12v = full, 0v = empty) or is it more subtle than that? Is it just a 12v signal or is there some voltage stabiliser?

I have a scrap BX at the moment from which I could salvage some bits (like I did for my rev counter), but don't want to waste a lot of time and effort replaceing the wrong bits!

(And unfortunately the trip mileometer is also not working either - at least, can't reset it, which makes it a bit useless.)

Any help / suggestions / advice / comments welcome. Well, except for "Yes, I had that, so I got rid of the car."

[Defender110]

Lift the back seat base and there are 2 access pouches under the felt, one is for the sender unit and a wiggle / clean of the wire connectors often cures any problems, unfortunately not in my case ;-(

[Tinkley]

As mentioned above the access is through the felt. If it has not been 'looked' at before you may have to complete the detachment of the felt ring to access the sender. As far as I am aware it is a rheostat type device. I've had 2 cars that the light went/goes on with at least 50 miles left in the tank and one where it hardly lights up at all until you are out of fuel. Been lucky to run out very close to petrol stations!.

The sender is in an 'aluminium' tube, if I remember correctly the more inboard of the 2 hatches. I've put a Broquet catalyst in mine to supposedly help the valve seats and economy. Hard to tell, but doesn't do any harm and the old Athena could do 50mpg + at a registered 70 on the speedo. Bit of a pig to fish out when I swapped cars though....

The sender does not look like a repairable to me, at least when I looked to try and change the time the warning light would indicate on the dash.

[Stuarted]

Thanks folks.

Located sender OK, under rear seat (it is at the front edge of the seat pan, more-or-less mid-way across the car).

Unplugged and re-connected connector with ignition switched on: gauge slams "full" when sender connected and "empty" when disconnected, with a distinct "clunk" from the gauge in each case.

I presume therefore that the gauge, the wiring and the connector are OK, and that the sender is faulty - either an electrical short circuit, or the float (if there is a float) is jammed at the top position. As I said earlier, the gauge had been playing up for a while, dropping only slowly as the tank emptied and then continuing to show more-or-less "half full" as the tank continued to empty, and this would presumably seem to suggest a jammed float rather than a simple electrical "short".

Either way, I guess the fix is to replace the "sender" with one (one hopes, a working one!) from a scrap car. Does anyone know, please - does the plastic locking collar holding the sender in place just simply unscrew?

[Stuarted]

Hmm - rolling news - gauge has now just started to show very, very slight drop in fuel level after 160 miles driving from a full tank.

It may be just showing about half to a quarter of a tank more than is there - a kind of permanent offset.

Presumably stiil the sender playing up and probably still needs replacing.

Have any other people had problems with odd fuel gauge indication?

Has anyone else removed / replaced the sender unit, please? How do you undo the plastic retaining ring? I presume they're not regarded as reparable but has anyone had one apart? What's inside the unit and how do they work?

[MULLEY]

If you've got the double fuel tank on your BX, & depending upon whether its a petrol or diesel, the fuel guage totally ignores the smaller secondary tank, it only registers the amount of fuel in the main tank. On my TXD it only starts to move from full when i've done 200+miles, a petrol will be less of course

[bx_pallas]

My sender was full of a rusty brown sludge, when I opened it. The litte bore in the bottom was clogged, so the fuel level inside the sender hardly could equilibrate with the outside level. It took about 24 hrs. (depending on the temperature) for the gauge to go from empty to full after refuelling, and when driving long distances on the highway, the fuel consumption was faster than the gauge could follow, so you would run out of fuel with the float still floating in fuel
Electrically and mechanically the sender was fine, I just had to slide the aluminum cylinder off, take the sludge out from it and rinse it with some diesel! It's working normally now.

[mat_fenwick]

/\ I've seen that happen too.

[rutter123]

Fuel gauge on tzd has a similar prob, just tells you wotever it wants regardless of how much fuel is put in, i just rely on each £10 of diesel covering about 60 miles, set the trip counter every fill, wait for fuel warning light (which is still working well) and refill, seems fairly accurate.

[Stuarted]

Yeah, but my trip isn't working (didn't work on my previous BX either. Anyone know how to fix this please? Reads mileage OK but cannot reset it to zero.)

[mat_fenwick]

Drive around until it's back on 0000?

Does the button have undue resistance to pushing it in? Mine does occasionally, but will push in perfectly a few miles down the road. I assume wear means that something doesn't line up properly every so often, and I don't want to force it. I'd be interested to know if you find a solution.

Back to the gauge sender - have you tried cleaning it out at all? I've once done it without a strip down; just by spraying solvent into the bottom hole until what came out was clean.

[barry badger]

I've recently repaired the tripometer on one of my tzds, it was too much friction between two plastic components. As they try and slide against each other they jam. A tiny dab of grease and it works perfectly.

[Stuarted]

I've recently repaired the tripometer on one of my tzds, it was too much friction between two plastic components. As they try and slide against each other they jam. A tiny dab of grease and it works perfectly.

How easy is it to get at and get into, please?

[Stuarted]

Back to the gauge sender - have you tried cleaning it out at all? I've once done it without a strip down; just by spraying solvent into the bottom hole until what came out was clean.

how easy is it to get the sender unit out, please? Does the plastic retaining ring just unscrew? What kind of tool do you need? Don't want to break it and leave the fuel tank un-sealed ...

[mat_fenwick]

The ring just unscrews, yes. Tap it round with a screwdriver, although I'm sure there is a special tool for the job...