How reliable are fuel level senders?

Had our van for a few weeks. Before we got it, the fuel gauge wasn't working and to fix the problem, it had the fuel level sender replaced with a new one.
Last weekend, on the way to Alive &V-Dubbin, it stopped working again. When the tank is full, the gauge reads 3/4, after about 20 miles it drops to empty ( off the scale). Each time I fill up, it does the same. To me, these symptoms suggest a problem with the resistive tracks on the sender unit. However, the sender is new. Today, I took the signal line off the sender and connected it to ground, the gauge moved to full as it should. I'm thinking the gauge is OK. That only leaves the sender and the voltage stabiliser.
Are fuel level senders reliable? I don't want to spend £50+ on a new sender unless I'm certain it's the problem. Is there a way of easily testing the sender in situ?

 

Hi - I had this problem when I first came home with my T2 Pickup. I fitted a new one and found that it did almost the same.
After some searching online I did find this to be a common fault. Interestingly the fault lies with the arm in the tank where it connects to the sender. Your best bet is to empty the tank, drop the float to the bottom and see if it reads red on the dash. then raise it with some string up to the top and check for full in the cab.

If it works which I suspect it will, you have to put a gentle set into the linkage connection between the sender and the float arm so that it reads in the middle of the two.

Now when my one is full it reads at 3/4 full. When its just off the red its time to find a pit stop quick.

Finally, if when testing you find your dash dial doesn't move at all, its most likely that its filament wire has burnt out which is why it has stopped reading.

Due to the time doing the above, most garages plug a new unit in and charge you as job done.

Good luck. It will take 20/30 mins but well worth it in the long run.

 

Fitted a new sender a few months ago cos ours was at best intermittent and read empty most of the time.

The new one reads about 7/8 when full and has about 2 gallons left when empty.

 

I think it's behaviour has tested itself for you and I agree the wire winding has broken.

 

Neither of my vans has had an accurate gauge - this one is slightly more vague I think but it's one of those things you get used to I guess.

 

These things drive me friggin mental... I've given up on them now. .. they always lie no matter what...

 

I tend to use an app on my phone, keeps track of fuel fills and distance covered, so you get a nice average mpg....
My fuel gage reads full when full... Then at about half full, drops too empty....
With the app I know the mpgs and distance covered.. About 200 miles and I am running on fumes.... Well that was with the progressive... Dunno what the dells are going to be giving as far as mpgs go... Found I am driving with much more enthusiasm since I fitted them

 

I work my MPG out the old fashioned way and log it in a book - but that app sounds good NatchoNatchoMan is it for iphone? My current calculations tell me I am getting 23mpg on a 'combined' journey type. Hopefully a bit more on a motorway run at between 60 & 65mph. So far I've been filling up around / before 200 miles.

 

I have it on android..
https://play.google.com/store/apps/details?id=com.aguirre.android.mycar.activity.beta

Its good cos you have multiple profiles for different cars, works out running costs servicing etc.....
Even makes pretty graphs!

 

I have similar problem with my bug. Put a little petrol in and it shows full and then will suddenly come down. When I'm going up and down hills the gauge moves up and down.

The last owner put a new sender in it so that shouldn't be the problem. I've also looked through some of the work its had done before the last owner and it looks like this might be an ongoing problem.

It drives me nuts but at least the gauge on the bus works

 

Mine says full on left handers and empty on rights.

 

Wiggie has developed an interesting feature where once the fuel gets below the half-full mark it often shows, say, an eighth less than it did when you stopped the night before, and once you've been going for about ten minutes (of which at least 5 are usually on dual carriageways or motorways due to where I live) the level slowly starts to rise! It soon drops again, though, when you come off the faster roads and your speed goes below 30.

I had to give myself a stern talking to the other day when I found my mood cheering up as the needle rose - I'm short on cash atm and didn't want to fill up, but false optimism is not something I should be lulled into when I know I haven't caused the needle to rise by filling him up!

 

So the faster you go, the more petrol you have - brilliant! I wouldn't mend that.

 

Mine used to work OK and then the tank was removed by my then VW specialist, after it was put back it has always read 3/4 full when full and seems to still have fuel in when reading below the big R

 

Filled the van up tonight to full, ready for a weekend camping trip to Norfolk. Gauge is showing 3/4 at the moment but expect it to drop rapidly once we set off on Friday. I'll watch the mileage, is 180 miles a reasonable estimate of the tank range or should I fill up sooner?

 

It's a 79 van so has a 2 litre fuel injected engine.

 

Small update on this from my corner of the world... I spent a chunk of this afternoon walking over 3 miles to get petrol after believing the gauge when it said there was over a quarter of a tank left. I guess it's even more unreliable than I realised! D'oh!

Stevie, sorry mate I don't know tbh, but my best advice would be "less than you think and keep a full petrol can on board in case it's even less than that!"

 

You should easily get 180 miles from a full tank, but as Surfgir1 says, carry a spare gallon with you.
You can quite easily cut a small hatch above the tank to get at the sender unit. I did mine a few months ago. Still hasn't fully fixed my gauge problem but has improved it a bit.
An easier thing you can try is to clean up all the connectors on the back of the fuel gauge and those that connect to it. In fact clean up all the connectors on the dash while you're at it.

 

My engine was out yesterday. I asked the engine builder to fit me a new fuel sender as well as changing all the fuel and breather pipes. He told me not to bother changing the fuel sender unless my current one was completely knackered. He told me the new ones are far more likely to fail. If it ain't broke, don't try to fix it!