Fuel gauge.....

Post Wed Sep 18, 2013 5:09 pm

I'm getting the feeling that my fuel gauge is lying to me quite a bit!!!
Although I think there may be a problem developing else where and the car does seem rich, the fuel gauge is now taking the peepee!!!

Since I've realised I'm filling up a lot recently, I've noticed the gauge seems to vary in position by up to 10mm at times!!!
I can be idling with just over quarter of a tank and when I floor it, I've suddenly got nearly half a tank again!!!
It does also seem to fluctuate a bit sometimes when just idling (by 3 or 4mm sometimes!!!)

So I'm guessing some kind of dodgy earth or loose connection somewhere???
Where should I start looking???

I've also changed the clocks on this car in the past, but have only just become aware that there is a difference in them for different tank sizes!!! Could I have used the wrong one??? How can I tell???

The car is a 1990 M20 Touring (was 2.5, now 2.7!)
Think the replacement clocks I used came from a 320 touring, but I wouldn't want to guarantee it!!!

Cheers,
Rob.[/code]

Post Mon Sep 23, 2013 10:24 pm

Have you Checked the brass nut on the back of the dash cluster where the fuel guage sits? Heard it can work loose and cause issues.... Worth a look

Post Tue Sep 24, 2013 11:39 pm

Will check that first when I get a chance!!!

Strangely been behaving ok since I posted that - until this afternoon!!!

Post Wed Sep 25, 2013 12:15 am

Mine does a very similar thing, initial start the gauge will read say, half a tank, after a short drive like a grandad the needle can shift as low as a quarter, if I give it some beans it can return right up to or greater than the previous half full reading!

Post Wed Sep 25, 2013 9:40 pm

my fuel gauge changes as I go round corners goes up one way emptys the other
theres two senders in the tank I think one will not be working properly
I can gauge fuel usage well enough as it is though

Post Thu Sep 26, 2013 8:34 pm

Mine was a nightmare yesterday and then fine again today!!!

Taken from the wiki:

If your fuel gauge is flickering, a broken sender is a common culprit. To check, pull the plug off them, one at a time, and short together the relevant pins in the plug, with less than half a tank of fuel on board. When the faulty one is shorted, the gauge will give an inaccurate but steady reading. Conversely, when you short the good one you will get an inaccurate and still jumpy reading.
If the gauge is still jumping around with both senders shorted out, then the brass nut on the back of the gauge, or the wiring (unlikely), is at fault.

I'm worried I'll test them and not find a problem, as mine seems to be quite intermittent!!!

So on realoem - is that parts 5 & 9 below???
Are they not the same part number and does anyone know if they really are that expensive???
I was hoping they would just be a few quid each so I could just replace them to either sort it, or rule it out!!! (I know this will upset several people who will say test before you replace anything - but I'm very short on time to play with this at the moment!!!)

05 SENDING UNIT ASSY METAL TANK 1 16141152266 $138.71
09 SENDING UNIT ASSY METAL TANK 1 16141179720 $138.71

Post Thu Sep 26, 2013 9:04 pm

Text of that wiki article seems familiar!

miniblob wrote: but I'm very short on time to play with this at the moment!!!)

Tales a few minutes to fit a short on one of the senders, then you just use and drive the car as normal, apart from remembering not to run out of fuel.
Drive it for a week with each sensor shorted in turn if the fault is intermittent. The low fuel light should work as normal.
Two new sensors would be an appreciable percentage of the value of your car, and are totally unnecessary. A second hand one will be perfectly adequate - only a small percentage of sensors ever go wrong. I don't think I've ever seen one.

Post Fri Sep 27, 2013 12:37 am

The low fuel light should work as normal.

Hmmmmm, when should it come on???
Come to think of it, I've never seen mine light up on this E30 and I've had it below the bottom of the gauge (according to this dodgy gauge!!!)

Two new sensors would be an appreciable percentage of the value of your car, and are totally unnecessary. A second hand one will be perfectly adequate - only a small percentage of sensors ever go wrong. I don't think I've ever seen one.

Fair enough - I shall have to do some testing then!!!
Just thought it might be a cheap part to replace, but as usual, I'm very wrong!!!

I'm assuming the fuel sender from a K plate 318i Cabby is of no use to me??? (As I have one sitting on the drive in bits!!!)

Post Fri Sep 27, 2013 8:50 am

RH sensor is identical (remove it with the rest of the pump assembly still in place, or you will damage it). LH sensor is also identical, if it exists.

Post Fri Sep 27, 2013 9:03 pm

Superb - I'll keep hold of that then!!!
Cheers Brian!!!

Post Fri Sep 27, 2013 9:45 pm

Hi guys!

I recently got a problem with my fuel gauge, it ain't the same as TS but I thought that hijacking this thread instead of making a new one would be better..

The problem I got is that the fuel needle just stopped working after I had been running low on gas, fill'd it up with like 19-22L, the needle goes up like normal. I went home and the day after the needle wont move more than just that mm when I turn the ignition on.

So do any of you have any clue what my problem may be ?

The car I am talking about is a e30 320i from 1987, and I'm from Sweden if that would matter.

Thanks in advance // Bertil

Post Sat Sep 28, 2013 9:36 am

Thanks for you answer!

I went out to try that, but my needle didn't go the way you described..

I made a quick vid to show you what I mean:

Post Sat Sep 28, 2013 12:09 pm

Will's instructions on bridging wires aren't too clear on what he meant.
You will have three wires in the plug to the sender - one plain brown, one brown/grey and one brown/green.
If you link the plain brown to the brown/grey, then the low fuel warning light should come on.
If you link the plain brown to the brown/green, then the gauge should go to full with the ignition on.
Your vid. looks like you may have connected the brown/grey to the brown/green.