I need info on the correct position of the fuel sender O ring. The schematic shows it between the sender and lock ring. Some posts discussed ways to keep it from slipping when tightening the lock ring but I also read a post saying the ring goes between the tank and fuel sender, then the lock ring.

I used vaseline to hold the o-ring in place.

I believe the o ring goes between the tank and the sender. The tank is 'grooved' for the o ring. I've replaced a few and had no issues with keeping the o ring in place when putting the sender unit back in.

I believe there is a metal "tab" that is part of the tank bung, that helps hold the o-ring in place. A non petroleum or synthetic grease is a good idea too. Some greases can dissolve some o-ring materials.

My line of thought was that if the o-ring has to stand up to gasoline, it probably was not very susceptible to deterioration by petroleum based products.

This should be true and probably is true with OEM stuff. You never know with the replacement stuff.

I believe the o ring goes between the tank and the sender. The tank is 'grooved' for the o ring. I've replaced a few and had no issues with keeping the o ring in place when putting the sender unit back in.

I recently replaced mine, this is correct.

The O-ring is petrolium resistant, so use a heavy petro based grease to hold the Oring in place and prevent tearing it if the sender moves durring lock ring installation.

Thanks everyone for the information. I would be completely lost without this web site.

Cygnusx1 is right, between fuel tank and unit

Attached is a picture, I recently

replace my fuel tank