[rokndad]

Doug,

One other thing you might try if for some reason it comes out too easily again. Use the smaller O-ring you last put on, but before you put it on, and without using a second O-ring, cut some thin (the thickness of the groove that the O-ring fits in) strips of electrical tape and wrap that around the cap's groove before you put the O-ring on. This pushes outward the thinner O-ring and gives you control over exactly how big an outside diameter you end up with. This is a trick I used on the cone shaped neoprene ring on my distributor shaft and it now it doesn't leak a drop. And the cap comes off and on easily every time. Cheers.

Tom