Fuel tank leak??

[BBF]

Started the car the other day and quickly noticed the fuel gauge was pegged empty with the computer saying range : 0 miles. 
 

I was convinced someone had somehow siphoned the fuel out, however after filling up with 20L from an unwieldy kerry can, i noticed a small patch of diesel on floor. 
 

I’ve never had an (apparent) fuel leak before, and there have been no incidents, prangs, object collisions or anything like that i’m aware of. I did wonder if it wasn’t a leak but just some side effect of filling with a glugging jerry can…
 

I’m just fishing for pearls of widom before blindly handing this over to a garage to sort out. Like anywhere in particular to look or things to lookout for. Its a 2016 diesel

estate.
 

 

[J.R.]

That is normal if any of the fuel splashes back into the filler neck.

 

MK1 and MK2 Octavias were very slow fillers and the pump would frequently cut out especially if there was not enough defoamer in the fuel.

 

Filling to the brim and then some I always leave an incontinence patch like that on the forecourt.

[J.R.]

If you look at your photograph you can see splashes of diesel all over the lower bodywork, those will have overflowed the filler neck having overcome the capacity of the drain tube so I definitely would expect to see a patch from the drain tube in that exact position.

[ords]

Park it on a dry surface and see if there are any wet patches

 

[cheezemonkhai]

Thieving b stewards and plastic fuel tanks combined with anti siphon devices mean that the preferred method is to drill the tank.

 

It’s possibly splash back, but check the tank for a small drilled hole.

[BBF]

So there is no leak, the fuel on the floor was just a bit of overflow from sloshing fuel coming back into the filler area.

 

So it’s either been syphoned without leaving any marks or i managed to somehow completely ignore multiple low fuel warnings.

 

weird.

[J.R.]

Or the dash display was talking crap, or the fuel sender is sticky, I had the former on my MK1 Octavia and ran out a few times.

 

Set the trip meter next time you fill up, keep an eye on the miles travelled and the indicated fuel level, you should see if there is a discrepancy.

[CookieMonster87]

Something similar happened to my Wife’s Megane. Started it up one day and the digital dash was at empty and the range 0. She was adamant she’d only filled up a couple of days before and hadn’t done many miles. Drove to the local garage and stuck a tenner in, gave the top of the tank a whack under the back seats and sure enough the tank was showing 3/4 when we started up.

 

I doubt you would have missed multiple warning to the point of the tank being empty. The low fuel warning comes on way before you run out.

How big is you tank? You said you’ve already put 20L in, see how much it takes to brim it and then you’ll know how much was in there to begin with.

[BBF]

So i had a 20L jerry can, and as i started to refill the tank with that i was watching the fuel gauge slowly come up from the bottom. After 20L the rank was about 40% full, see pic. This all seems correct as it’s a 50L tank

[cheezemonkhai]

Could have been some crud in the tank. 

If the same happens again with the no warning, then warning, I'd look at having the tank cleaned and the sensor/pump replaced.

 

It's money, but it's a lot cheaper than running out on the way to somewhere important.

[CookieMonster87]

9 hours ago, BBF said:

So i had a 20L jerry can, and as i started to refill the tank with that i was watching the fuel gauge slowly come up from the bottom. After 20L the rank was about 40% full, see pic. This all seems correct as it’s a 50L tank

Ah, in that case I’d go with what @J.R. said and monitor your mileage vs consumption. If you’ve done a fair few miles and haven’t seen the gauge move for a while then it’s a good sign there’s a signalling or indication fault.

 

You never know, it may never happen again.

 

In the case of the my wife’s Megane, that fault never reappeared. We assumed the car was having a moment and that the drop of fuel we put in/thump of the tank made it wake up 😂.

[CookieMonster87]

@BBF any update on this mate?

[BBF]

Hi, thanks for following up. I’ve done nothing since other than fill up, check that everything is an expected and drive. There have been no anomalies since, no leaks, low readings or anything. 
 

Starting to wonder if I somehow missed multiple low readings and ran it completely (but not quite) empty. It’s pretty weird. 

[CookieMonster87]

@BBF or the sender got stuck that one time and tricked you in to thinking you had more fuel than you did.
 

If you’ve ran the car down until the warning light comes on (a bit risky at present) and have covered the appropriate mileage I’d say you’re all good and it was a one off.

[bigjohn]

I once ran out of petrol in my mk I Octavia. The day before I'd been driving like the Pope through endless miles of speed controlled roadworks coming back to Yorkshire from Stanstead Airport - no low fuel light. The next day I tried to drive about 10 miles into town through heavy traffic- orange light came on and I fully ran out about 7 miles later before I had chance to fill up. The fuel gauge was on zero but I hadn't noticed really without the light coming on.  I wondered if it was because the car computer was presuming that I'd still be maintaining the very high mpg from the previous journey.  Another clue was I was driving up a hill when I ran out -there was no spluttering - it just stopped. 

 

I / it didn't do it again in 19 years of ownership!

 

Edited 27 September, 2021 by bigjohn