18-02-2021, 11:52 AM
What I mean is, the petrol going in, especially from a modern forecourt pump, causes petrol fumes and air to come out of the tank at a velocity capable of levitating the ingoing petrol out of the filler pipe. The RM petrol tank and filler commonly cause this to happen if you do not pump the petrol slowly. Indeed, the RM rileys have two filler caps for the single tank, one on each side of the car and Nuffield (whispered in current forum) acknowledged the issue with back pressure by the following instruction in the vehicle handbook. (see attached) Incidentally, there is no problem with sucking a vacuum in normal operation. My original question was "Has anyone experienced issues with backpressure when filling an A7 tank (with breather) I assumed there was sufficient air leakage around the filler cap for tank vacuum not to be a problem. As no-one has come forward to state there is a problem...I assume there isn't. So why did Austin fit the breather?