Petrol guage or sender?

[Brian28]

The petrol guage on 318i has stopped working, it was about 3/4 full on the guage (and in the tank!) but stopped. I've swapped the clocks for another set (320 if that makes a difference) but no change. I've earthed the wires at the sender unit, fuel level light comes on but guage doesn't budge. With the sender wires reconnected, I've taken the sender from the tank, turned it upside down a few times and right way up again, this triggers the fuel level light but the guage still registers zero. Anything else to try before I buy a sender unit? (Bit miffed as I've sent two breakers to the scrappie recently)

Cheers
Brian

[Brian28]

Ok, update is I've swapped the sender with the one on the race car and it works fine. I've tried a third set of clocks in the car just in case, but still no signs of life from the petrol guage. Does anybody know if there is a fuse in the line between the sender and guage, or the route of this wiring, as the most likely problem is a break in the wire somewhere. I haven't done or moved anything to disturb the wiring and create a break, but a bit lost for other ideas.

Cheers
Brian

[Brianmoooore]

No fuse, and only one plug and socket - under the right hand side of the seat squab. Brown green wire all the way. Earthing it at any point should send the gauge to full.
Note - Some tanks use two senders, one each side, and the wire from the cluster goes to the left hand one first.

[Brian28]

Thanks Brian. I've done a bit more fiddling this morning and now I'm baffled. I've earthed the wire at various points, from the clocks through to the back seat. Get a reaction from the guage as far as under the glove compartment, but nothing under the back seat passenger side so there's possibly a break in the wire somewhere in the loom along the passenger sill. (Not sure this is actally possible but lost for any other explanation).

The second thing that I'm lost with is the guage itself. When tested directly on a battery does exactly as it should, ie registers full. When in situ, earthing only moves the needle to about quarter full. I've tried this with a couple of guages and still the same, about 30/45 degrees movement. On one I tried moving the needle clockwise on the stalk so the rest position was about half full on the dial, earthing it only moved the guage to three quarters full. Everything else electric/electronic on the car seems to be working fine, the guage was fine until yesterday when it suddenly stopped working. Wasn't doing anything at the time DIY that may have caused it, just moving the car on the driveway. Any ideas?

Cheers
Brian

[Brianmoooore]

. I've earthed the wire at various points, from the clocks through to the back seat. Get a reaction from the guage as far as under the glove compartment, but nothing under the back seat passenger side so there's possibly a break in the wire somewhere in the loom along the passenger sill.
Brian

That sounds very likely. Where exacly is anyones guess.
Wire goes along LH cill and across back seat.

[smithy318i]

Anyone know the resistance of an empty tank? Thats the value on a meter across the terminals when there isnt any fuel in the tank.

And are 1 sender tank senders different from two sender ones ??? (if you understand that)

Im still having trouble with connecting two in series

[Brianmoooore]

Anyone know the resistance of an empty tank? Thats the value on a meter across the terminals when there isnt any fuel in the tank.

And are 1 sender tank senders different from two sender ones ??? (if you understand that)

Im still having trouble with connecting two in series

Just measured one. 4 ohms full, 60 ohms empty.

[smithy318i]

Cheers Brian. My cluster appears to be designed for one sender. connecting both in series doubles the resistance. 60Ω to 120Ω = needle on zero = half full = zero

[Brianmoooore]

Not sure, but I think it's the senders that are different with the two sender type, not the gauge. Twin senders are definitely connected in series.

[smithy318i]

thanks for the help

[Brian28]

Thanks from me too. Sorted now, I spliced another wire into the loom. Still don't know why it wasn't reading full when earthed, the only car I've come across that doesn't. Mebbe just another BM quirk