Problem in filling petrol with "Auto Cutoff" feature

[RajeshK]

Dear All,

I am using a Santro zip plus 1.1LP which clocked 52K kms now. Few days back, I went to a petrol pump and asked them to fill full tank with autocut feature in the filling pump equipment. I already have half tank petrol, but to my surprise the device stoped just after filling only 5Ltrs. I asked them to retry, but stopped immedietly. So there is a problem either in the device or my tank. So used manual mode (Seek and try method..!!) and filled the tank with another 15Ltrs.

After some days, again this experience repeated this time autocut went off a little later, 7Ltrs. . So realised...problem is with me only...The autocut feature is not working in my vehicle at all.. But fortunately it accepting petrol..!!

Can any one throw some light on this issue...? Any possible way to check for any issue..? I am not able to see any issue in the tank with my naked eye.

Thanks
Rajesh

[BaCkSeAtDrIVeR]

Probably a very narrow petrol inlet into the car's fuel tank. Auto cut out feature works due to the back pressure caused by air comign out of the fuel tank. WIth very narrow inlets into the car's fuel tank, (design constraints, or deliberate - to avoid evaporation) back pressure may set on too early. Other cars too have this, and reported in other threads.

[abhinav.gupta88]

Similar thing happened with me. THey say happens sometimes.

But then they did it again and it worked

[RajeshK]

Originally Posted by BaCkSeAtDrIVeR

Probably a very narrow petrol inlet into the car's fuel tank. Auto cut out feature works due to the back pressure caused by air comign out of the fuel tank. WIth very narrow inlets into the car's fuel tank, (design constraints, or deliberate - to avoid evaporation) back pressure may set on too early. Other cars too have this, and reported in other threads.

Thanks a lot for the input. But in my case it was working earlier with those same petrol pumps, and suddenlty stopped working in a fine day. So I think the inlet width is not in question, unless some thing really blocks it from inside

[diabloo]

It could happen the other way too - the cutoff never happens, resulting in fuel spillage.

[gd1418]

In the autocut feature, what the attendants normally do is to lock the valve at its highest position resulting in the fuel gushing out of the nozzle at high speed. This results in foaming thus creating back pressure which activates the cutoff feature.

[RajeshK]

Originally Posted by gd1418

In the autocut feature, what the attendants normally do is to lock the valve at its highest position resulting in the fuel gushing out of the nozzle at high speed. This results in foaming thus creating back pressure which activates the cutoff feature.

Thanks a lot for this info. But in my case, it was working earlier but now suddently stopped working

Thanks
Rajesh

[Rehaan]

Originally Posted by BaCkSeAtDrIVeR

Probably a very narrow petrol inlet into the car's fuel tank. Auto cut out feature works due to the back pressure caused by air comign out of the fuel tank. WIth very narrow inlets into the car's fuel tank, (design constraints, or deliberate - to avoid evaporation) back pressure may set on too early. Other cars too have this, and reported in other threads.

Not really "backpressure" but the rest of what you have said holds true.

RajeshK - take a look at this to get a better idea : HowStuffWorks "How does a gasoline pump at a filling station know when the tank"

cya
R

[RajeshK]

@Rehaan, Thanks a lot for the info.
I have tried filling with the autocut feature one week back and found that its failing again. But during the last week, I have quiet a bit, clocked around 2K kms and after that tried in the same petrol pump. Interestingly...it works..!!

Need to check this again in the next filling

Thanks
Rajesh

[Rehaan]

RajeshK,

Maybe it is a faulty auto-cutoff at the pump you are filling at? i.e. the vaccum tube (in the filler handle) could be clogged or blocked which is causing the auto-cutoff to happen earlier.

cya
R

[ph03n!x]

But didn't RajeshK say that it happened in two different pumps?

[Ricky_63]

If you want to get the right amount of fuel before cutoff, ask the attendant to fill at the slowest setting. This is something they avoid in order to save time & I am told the method aves some little bit of fuel to the gas station.

I always insist on filling at the slowest speed & usually get the amount of fuel I expect to get in the tank..


Cheers

[RajeshK]

Originally Posted by ph03n!x

But didn't RajeshK say that it happened in two different pumps?

Yes, It happened few different pumps. But there is pattern in all my trials, it was after a long bumpy drive.The speed of the filling gun may be the culprit, but this added the confusion.On a sunday evening, I tried filling in a slower speed at my regular pump and the auto-cut off worked quiet smoothly.

Originally Posted by Ricky_63

I always insist on filling at the slowest speed & usually get the amount of fuel I expect to get in the tank..

Cheers

Finally the slower speed worked for me. Thanks for your suggestion.

@Rehaan, your inputs where were really helpfull...thanks a lot

Thanks
Rajesh

[Thad E Ginathom]

In UK, where it is all self-service, I find some pumps are more sensitive than others. I had this problem regularly, though, with my last car there (Rover 620) and figured out that it did not happen if I held the filler at a particular angle. The angle looked wrong, but worked, cutting out only when the tank was actually full.

[lancer_rit]

Reviving an old thread.

Auto-cutoff used to work perfectly for my Lancer for many years, but over the past 2 years or so, a lot of times it cuts in too early - even when the tank is 4/5th empty. For some pumps, the attendant needs to fill fuel manually. The frequency of auto-fill cutoff prematurely has gone up a lot in the last year, and now it happens 70-75% times ...

Now, I tried to read through this and a few other threads on the forum, but didn't find any clear explanation why the behavior should change for my car after several years ? If it was always facing the same issue, I could understand talk about fill speed, filler neck etc etc ...

Have been wondering if dirt etc in fuel tank / fuel pipe could, somehow, impact this ? Basically, I am clueless on this topic :-(