03-02-2023, 09:58 PM
(This post was last modified: 03-02-2023, 10:00 PM by John Cornforth.)
Hi
From memory, the sender has 6 regular spaced plain holes. The screws go into tapped holes in a ring shaped boss in the top of the tank, with a cork gasket to seal. The thread type and size has been argued about on this forum several times, and I can't remember the final outcome. I suspect there are several similar sized threads, hence the confusion. You can use whatever you see fit.
The sender relies on the tank being earthed. The tank U-bolt fixings were originally set in rubber strips, so I suspect earthing was actually via the copper petrol pipe back to the engine. This is fine as long as you don't put in a rubber pipe section ! You could also run back a dedicated earth wire from the sender body if you want to be certain. The gauge earthing is equally tenuous, and relies on the gauge body being connected to the instrument panel and that panel being connected to the body. Again, a dedicated earth wire to the gauge earth stud might be useful.
One thing which makes the senders unreliable is that the "hot" connection has a tufnol insulating sleeve where it goes through the body. Smiths had the bright idea of trapping the earthy end of the resistance wire in the gap between this sleeve and the mazak body. You can imagine how good that earth connection is after 80 years of corrosion, so dismantling, scraping and reassembly may be called for.
The resistance wire is wound on a thin former, and the 'finger' attached to the arm and spindle bears against it. Cleaning the surface with contact cleaner and ensuring that there is at least some finger spring tension at all points of the travel may eliminate any erratic behavior.
From memory, the sender has 6 regular spaced plain holes. The screws go into tapped holes in a ring shaped boss in the top of the tank, with a cork gasket to seal. The thread type and size has been argued about on this forum several times, and I can't remember the final outcome. I suspect there are several similar sized threads, hence the confusion. You can use whatever you see fit.
The sender relies on the tank being earthed. The tank U-bolt fixings were originally set in rubber strips, so I suspect earthing was actually via the copper petrol pipe back to the engine. This is fine as long as you don't put in a rubber pipe section ! You could also run back a dedicated earth wire from the sender body if you want to be certain. The gauge earthing is equally tenuous, and relies on the gauge body being connected to the instrument panel and that panel being connected to the body. Again, a dedicated earth wire to the gauge earth stud might be useful.
One thing which makes the senders unreliable is that the "hot" connection has a tufnol insulating sleeve where it goes through the body. Smiths had the bright idea of trapping the earthy end of the resistance wire in the gap between this sleeve and the mazak body. You can imagine how good that earth connection is after 80 years of corrosion, so dismantling, scraping and reassembly may be called for.
The resistance wire is wound on a thin former, and the 'finger' attached to the arm and spindle bears against it. Cleaning the surface with contact cleaner and ensuring that there is at least some finger spring tension at all points of the travel may eliminate any erratic behavior.