Is it possible to get an air lock in the fuel tank (diesel) filler pipe?

 

I wouldn't have thought so but I'm still trying to figure out what is going on with my fuel consumption.

I filled it full to standing liquid then did an 80 mile there-and-back run which read 51mpg on the display.

When I went to fill up  I put it in slowly to standing liquid but could only get in 4.1l (0.9 gallons).

 

Something similar happened a while ago after a much longer trip.

I suspect you have the same issue/observation that I’ve experienced.   I’ve been guilty of not stopping to fill after the 3rd click off.

I’ve found I could get almost 5 more litres in by v slow filling but then found the gauge did odd things.

I don’t think it’s a brand thing.

Edited 13 August, 20187 yr by Ryeman

Anything like a normal test suggests I get about 43mpg rather than the 50mpg the display tells me.

 

Still the issue of the far too frequent silly low display figures.

The display is notoriously optimistic, typically about 4 to 5 mpg better than actual,

You really need to do several tanks full and check against the other display in the maxidot with long term average. Zero this when you fill the first time. Compare with actual distance and fuel use.

 

Although the speedo is also very optimistic, the trip meter is spot on to within 0.1 miles over 100 miles. (Hence they could give you a true speed reading and exact fuel consumtion if they tried)

1 minute ago, kenfowler3966 said:

The display is notoriously optimistic, typically about 4 to 5 mpg better than actual,

You really need to do several tanks full and check against the other display in the maxidot with long term average. Zero this when you fill the first time. Compare with actual distance and fuel use.

 

Although the speedo is also very optimistic, the trip meter is spot on to within 0.1 miles over 100 miles. (Hence they could give you a true speed reading and exact fuel consumtion if they tried)

Yes, and still trying to work out why the readings for doing the same trip in identical conditions will read 51.2, 50.9, 51.1 and then 39.8.

21 minutes ago, Ashaz said:

Yes, and still trying to work out why the readings for doing the same trip in identical conditions will read 51.2, 50.9, 51.1 and then 39.8.

 

That could mean that one of the trips included a DPF regen.

The problem is that it happens every 3 or 4 days, too frequent for an auto-re-gen I would have thought.

I  had a similar "fuel gauge doing odd things" when I first had my 1.4 petrol, but it seems to have settled down now.

 

Tank to tank I am averaging an actual 44 mpg, the computer is a very consistent 8%  optimistic showing 47 mpg.

My best guess at the moment is that, on a good day, my 150 diesel (4WD) gets 43-44mpg.

6 hours ago, Ashaz said:

The problem is that it happens every 3 or 4 days, too frequent for an auto-re-gen I would have thought.

 

Depends on myriad factors; how far you travel, what speeds, what loads, the condition of the DPF, fuel quality, oil type and consumption....

 

It’s not out of the question.

There aren't many miles involved, it can even be 2 days running.

 

The car has only done 8000 miles in 15 months and I do what I can to keep the filter clean with my driving.

11 hours ago, Ashaz said:

The car has only done 8000 miles in 15 months

 

This could be your problem.

???

I regularly get the engine very hot for 20 mins.

Edited 14 August, 20187 yr by Ashaz
spelling

Long or short journeys?

Mixture of town and plenty of 80 mile round trips on good economical roads

Has it been emissions 'fixed' by Skoda?

No idea. I bought it new in April 2017 so after all the fuss.

Probably too recent to be affected then.

I would have thought so.

I have no idea what is going on with my car.

I knew I was going on an almost perfect journey for fuel consumption so filled the car up full to visible standing diesel.

I did the 62 mile journey which read 55.4mpg on the maxidot.

I then refilled in an identical manner and it took 9.33l.

That is 2.05 gallons which is 30.5mpg.

 

It's all very odd.

 

there have been comments a long time ago ref fuel filling on 4x4's-- there is apparently a 'hump' in the fuel tank which can apparently airlock causing a lower volume added  --  someone indicated parking on a slight slope could cause this situation  --  I suggest a search of this forum to reveal the situation!

I must admit I have never experienced it and my car is a 4x4!

Edited 20 August, 20187 yr by Frenchtone

Thanks, though it is always filled on the flat.

I wonder if there is a way of getting rid of the airlock if it is there?

12 minutes ago, Frenchtone said:

apparently a 'hump' in the fuel tank

 

Yes, complicated stuff with 'suction jet pump' as well as the main fuel pump.

https://skoda.7zap.com/en/cz/yeti/yet/2012-666/9/919-919031/

Ta.

I won't bother trying that!

I'll try the test again from virtually empty as I know the tank size.

I would guess that the 'saddle' shaped tank is causing your issues, coupled with the fact that you seem to fill up when the tank is still quite full? Maybe you need to leave it longer before you refill?