XJ12 Tank switch over shock!

[V12 Migaloo]

Had a nice drive up to Silverstone on Sunday in the XJ12, both tanks brimmed for a strong blast, emptied 3/4 of the RHS tank and went to switch over to the LHS and it wasn't pulling any fuel.... which was strange as its worked fine, with new solenoids, relay etc... therefore stopped to fill up the semi depleted tank. I opened the cap and immediately noticed a strong vacuum within the tank and the gush of vapor escaping and the air rushing in the tank was immense, quite frightening..... I could physically see the vapor and what's more the vapor was very warm. Getting this looked at today... obviously she switched over after releasing this air lock.. never experienced this before, even after changing the fuel tanks...

[Simpo Two]

It must have drawn fuel from the tank to create the vacuum, no?

[reddiesel]

Doesn't that Model have a Pressure Control Valve ? I recall similar problems on an old mates XJS V12