Interesting adventure. For the forth time I took everything apart. Washed and blew every hole I could find and studied the membrane. No holes or cracks but in all three membranes I noticed that the edges on both sides where the riveted disc sits (where the hole is in the old style) were crimped. The actual membrane appears to be just a bit too narrow to be properly held when things are bolted together. The first time the button plunger is pushed it actually pulled the edge away breaking the seal. These were new membranes purchased from a local supplier. I will ask where they were made.
I have some fuel resistant rubber sheeting. I made a new gasket and made it about 2mm all around bigger giving it better grip. Reassembled all. The tank works perfectly.
To summarize the various photos above, I now have four examples of membranes used over the years.
1 The old style with hole that used the aluminum plunger and two discs, washer, and nut.
2 The old style with hole but the the two discs were riveted together with the membrane sandwiched between
3 The new style membrane, no hole but those two discs fused together. The spring just sat on top
4 The 1958 version, new membrane, no hole, disc with lips to hold the spring in place. See photo.
Thanks so much to everyone that helped me on this project.
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