Mystery behaviour at petrol station

[Vicario]

I had a strange experience when filling up today. Micra 2020 (auto) petrol engine. I inserted the nozzle and began to fill. It felt as if there was a bit more pressure needed on the trigger. Put £15 worth in, so nowhere near enough to fill the tank. Paid and came to move off. Car went into limp mode with the check light on, rock hard brake pedal - you know the drill. Anyway, I switched off and on again, then selected Low gear and managed to move off. Petrol gauge was showing full, so totally incorrect. I parked round the corner, switched off and waited for 5 minutes. Switched on again and all OK, apart from the gauge which took about 15 minutes to settle at about 2/3 full. Has anyone got an idea what might be wrong? It was definitely petrol that I put in, by the way.

 

[Wayners]

I have a ford and if I turn engine off and start again quickly the fuel gauge is incorrect. Shows way less than is in tank. I need to turn ignition on and wait 2 seconds before stating so guage settles

 

[Burnerman]

Although I’ve no idea what’s going on here I certainly wouldn’t worry about it unless it happens again.
However, there will be a fault code stored which can be read if you want.....it’s probably to do with the emissions system, namely the fuel vapour in the tank which is inhaled and burnt by the engine.
John

 

[Koolpc]

I have a ford and if I turn engine off and start again quickly the fuel gauge is incorrect. Shows way less than is in tank. I need to turn ignition on and wait 2 seconds before stating so guage settles

Sometimes that happens with my car too.

 

[Harry Bloomfield]

Petrol gauge was showing full, so totally incorrect. I parked round the corner, switched off and waited for 5 minutes. Switched on again and all OK, apart from the gauge which took about 15 minutes to settle at about 2/3 full. Has anyone got an idea what might be wrong? It was definitely petrol that I put in, by the way.

My fuel gauge isn't what would at one time be called a fuel gauge at all. It has a saddle shaped tank, with two level sensors, which feed data to an ECU, the ECU then feeds an interpretation of the tank contents, to the gauge. The interpretation, includes a factor for the rate of fuel consumption. It also recalibrates its idea of what is a full tank, when you completely fill the tank. Start the car in the garage, and the gauge will read a bit low, but then as the car gets out on the road, and mpg increases, the gauge rises to a more realistic level.

If yours works something like this, maybe the ECU just got confused.

 

[Vicario]

UPDATE: Two weeks since I first posted. Today, the garage pump kept clicking off and refused to let me re-fuel apart from about 10 attempts when I managed to get a bit in. I left at about one third full when I really needed more for the M25 ( about 120 mile round trip). There was a very big whoooosh when I opened the cap too. Good news is that I didn't get limp mode this time. I think I've found the problem on YT but I'd be interested to hear what you guys and (gals) think.

 

[Mottie]

Blocked breather?

 

[foxhole]

Maybe you twisted the nozzle so the petrol was being forced back towards the nozzle triggering the auto off safety feature nozzle has to prevent flooding.

 

[Burnerman]

I'd go for a blocked or twisted breather pipe too.....unless this system has some sort of anti syphon device?
John

 

[Vicario]

There are lots of YT videos about this issue. Might be a problem with the EVAP system, apparently. But one bloke in the states used a solution that his mechanic father taught him. Blow air into the tank before filling up (when the level is below half) - this can unstick some valve in the emissions system which sometimes seizes up. I've got my leaf blower on standby so I'll let you know what happens. He has a canister of compressed air to do the job. Apparently the fumes in the tank can stop the nozzle from delivering petrol as it has a sensor.

 

[Harry Bloomfield]

I've got my leaf blower on standby so I'll let you know what happens.

That might be a bad idea - petrol tank, mixed with sparks from the commutator of an electric leaf blower, even more so, if it's a petrol powered blower.

 

[Adam_151]

That might be a bad idea - petrol tank, mixed with sparks from the commutator of an electric leaf blower, even more so, if it's a petrol powered blower.

I'd personally say the electric one might be worse, unless its got a mis-fire the petrol one should only have sparks inside the cylinder, the electric one will be generating them on the commutator as you say, and the surface temperature of a an engine is not generally hot enough to cause issues.

The vapor will also pool at ground level, rather than hanging around at any higher level, so he *probably* wouldn't blow himself up

Not that I'm saying its a good idea because it certainly is not! (I wouldn't have an issue with doing it on a diesel vehicle though) Better to blow air from some source of stored air and possibly ground the nozzle to the bodywork of the vehicle to reduce the risk of any static building up.

Now if we ever get hydrogen cars, the risk of accidental ignition with refueling has the potential to be much greater than it is with petrol!

 

[Vicario]

Where do you buy those aerosol canisters of compressed air? I think they're used to get rid of dust particles and other fine items that are difficult to see or get to. In the comments to the YT video, a responder stated that he used the tyre inflator that plugs into the ciggy lighter to disperse the vapours (and it worked); but there were several recommendations for canisters of compressed air.
A few years back my Chevrolet Aveo went into limp mode for no reason. I had to call the AA and the bloke did some OBD readings, took off the fuel cap and blew down the filler very vigourosly a few times. Nothing to do with filling up that time, but he said that when he gets that particular fault code he can always get rid of it. He thought that the fuel cap might be faulty but said that it happens if there's a build up of vapour in the tank so leave it and see, as it could be a one-off. It was! He also said not to just tighten the cap to one click, but turn it until it no longer moved.

 

[opps]

The Poundshop used to sell cans of compressed air- not sure if they still do though.

 

[Harry Bloomfield]

Where do you buy those aerosol canisters of compressed air? I think they're used to get rid of dust particles and other fine items that are difficult to see or get to. In the comments to the YT video, a responder stated that he used the tyre inflator that plugs into the ciggy lighter to disperse the vapours (and it worked); but there were several recommendations for canisters of compressed air.

If such a small amount of air will work, I would imagine that one of those blocked sink drain pumps should work equally well.