[rsanges]

I use the spray can cap to keep stuff out of the filler neck ABOVE the flap/valve. Once the debris is into the recess above the flap/valve, there's no keeping it out of the tank when you open the flap/valve with a pump filler head neck. I do the same on my Ford Transit which has no cap.

 

[rsanges]

I put a spray paint can lid over mine. FIts perfectly.