Hi Everyone,

Hoping you can help me out here.

Whenever my 2002 KJ Verada's fuel reaches below a certain level, around 3/4 full, the car begins running very badly. Under moderate to full throttle it surges violently, almost like it isn't getting any fuel at all. At the same time I can hear a bubbling or hissing from where the fuel tank is located.

All of this goes away as soon as I fill the tank up again, and the car runs perfectly. Any ideas?

New fuel pump did not help.

My guess would be a breathing problem causing a partial vacuum in the tank as fuel is drawn out, eventually defeating the pump once it's reached a certain point, about 3/4 full. The hissing is probably air leaking through the cap or fuel being sucked back into the tank from the lines as the vac tries to equalise (that's a guess, dunno if that's even possible TBH). Rather than refilling at 3/4, try just removing the cap to relieve any vacuum and run the car, if I'm right everything will be fine until about half full when the vac will build up again. The cause could be a blockage in the purge control line or cutoff valve, I'm not too familiar with this area so hopefully someone else can enlighten us both!

Thanks for the advice Ensoniq!

Also sounds to me like it's something to do with the pressure in the tank.

I'm going to buy a vented fuel cap and see if that makes any difference. Apparently the cap allows air to flow into the tank if there is an obstruction in the vapor recovery or vapor management systems.

If that fails, I'll have the EVAP system looked at.

If you haven't replaced the fuel filter it might be the problem if it is nearly blocked - the extra volume of fuel can overcome some of the fuel blockage due to gravity and the fizzy sound in the fuel filler can just be the aerated fuel arriving back to the tank due to lack of fuel flow...

20Cents worth experience based on the same fault with a Jaguar

My money is on the venting of the tank. Check the charcoal filter in the engine bay. You may have a blockage between there and the tank.