Fuel tank problem

[Kev880]

My daughter has an 06 Suzuki Swift, recently when she has filled up with Petrol when she got home Petrol can be seen leaking from the around the filler cap. I looked at it last week and when I undid the fuel tank cap there was a whoosh of air so we replaced the fuel filler cap which cured that but she has just filled up again she noticed that once again petrol was running out around the cap. She says she only filled it until the trigger stopped so doesn’t appear to be over filling it yet when she gets home and removes the fuel cap there is petrol running out of the tank as if there is way too much in it!

[Saleen836]

The cap you have replaced wasn't faulty, the 'whoosh' of air when taking the cap off shows the pressure system is working, the replacement cap will leak as it isn't pressurising, what has most likely happened is daughter didn't replace the original cap properly, went round a corner and petrol spilt out!
Put the original cap back on and report back

[Kev880]

Daughter says the original cap was on properly and it has happened twice with the original cap and once with the new cap!

[GreenV8S]

This time of year the fuel in the underground tanks is relatively cool, and expands as it warms up. If you brim the car (without overfilling it) and then leave it parked, you could easily find fuel overflowing.

[paintman]

GreenV8S said:

This time of year the fuel in the underground tanks is relatively cool, and expands as it warms up. If you brim the car (without overfilling it) and then leave it parked, you could easily find fuel overflowing.

Your daughter needs to put a bit less fuel in. She's relying on the pump cutout so is filling right up into the neck & there is no room for the fuel to expand without leakage.

LPG users can suffer a similar problem in hot weather, it's normal practice to fill until the pump display slows right down/stops & if left out in the sun after filling the tank's safety valve can operate to relieve pressure.

[E-bmw]

paintman said:

LPG users can suffer a similar problem in hot weather, it's normal practice to fill until the pump display slows right down/stops & if left out in the sun after filling the tank's safety valve can operate to relieve pressure.

Never heard that one before.

An LPG tank can only fill to 80% maximum for a start & it should be 100% impossible for 25% by volume expansion to occur on a tank that is 100% in the shade and to cap it all the relief valve is set at 110% of tank maximum pressure so it would actually need to be well over 25% expansion by volume..