Correct Installation of Fuel Sending Unit

[z3beemer]

 Working on a 73 240Z Restoration.  I just ordered an O ring and locking collar for the fuel tank sending unit. The FSM shows the sending unit going into the tank, then the o ring on top of that, then the locking collar.  Is this correct?  This would result to a metal to metal fit between the tank and the sending unit and offer little sealing from leakage. The one I took out had the o ring between the bottom of the sending unit and the fuel tank, then the locking collar, (which seems to make more sense).  Trying to decide which is correct.  Did the previous owned just install the previous one incorrectly or is the FSM correct?  

[Patcon]

Oring between sender and tank

[SteveJ]

Redneck Lock Ring Tool - 2.5 inches of 1 inch angle iron. Cut a notch for posts on the sending unit, and weld a nut on there (with a better welder than I possess).

I am curious, though, I looked through the 73 FSM, and I didn't see anything about installing the fuel sending unit. What exactly were you looking at? What section of the FSM?

[CanTechZ]

Were you actually referring to the North American parts book regarding seal order, I saw that it is incorrect there. I have noticed other errors in the NA parts book. Another source for info is the JDM parts book that can be found in the downloads, microfiche section, posted by @hr369.  The illustrations are much better than the NA parts book and it is a great reference. Here is a snippet from that book that shows the seal placement, as you correctly thought it should be.

Edited February 15, 2022 by CanTechZ

[z3beemer]

Thanks for the help guys.  You confirmed my suspicions / logic.  Guess you can't believe everything you read.

[SteveJ]

1 minute ago, z3beemer said:

Thanks for the help guys.  You confirmed my suspicions / logic.  Guess you can't believe everything you read.

Keep in mind that manuals like that were probably drawn by draftsmen, not the engineers and technicians who worked on the cars. The engineers probably had to review in a rush and approve for publication so Nissan could make the microfiche, print manuals, and get all of the materials out to the supply chain and dealerships.

It is almost without fail that I go back to drawings I approved years before and see some detail I got wrong. Keep that in mind as you look through the FSMs and other manuals. There could be an error lurking, but for the most part, the manuals are correct.