Topic: Fuel sending unit

[C5ZZ]

I have a Ford original in my 65 that goes to the full mark but not all the way to empty.
I have four other used Ford originals that either have the same problem or
reverse, they go to empty but not to full!
Any ideas?
 

[Bob Gaines]

I have a Ford original in my 65 that goes to the full mark but not all the way to empty.
I have four other used Ford originals that either have the same problem or
reverse, they go to empty but not to full!
Any ideas?

Hook up sender outside of the tank . I would rig up a long wire extension so you can sit in the driver seat and observe the gauge otherwise you have to have a helper work the gauge as you work the sender. Of course you have to provide a ground for the sender . Observe the way the gauge works as you move the float arm . You may just have a dead spot on the wrapped wire of the rheostat that needs a little sand paper from varnish build up. It could be the float arm needs a little bending . It could be a combination. Since you have a range of issues opposite each other indicates to me that your gauge is not the main fault.  I have revived a large number of senders over the years and these are just a few things that I have done in the past that have made a differance. Others may have a different way. 

[C5ZZ]

Thanks Bob for the info, I tested them how you mentioned and
thats how I came up with the differences in them, helped a
friend do the same on his car, we bend his tabs/stops and
that seemed to help his problem.

[J_Speegle]

Thought there was a possible adjustment done/possible at the gauge. Will need to look through papers and books to see if I can find the reference

[sgl66]

Thought there was a possible adjustment done/possible at the gauge. Will need to look through papers and books to see if I can find the reference

I was thinking the same, it's shown in here http://www.mustangandfords.com/how-to/interior-electrical/mump-1005-ford-mustang-instrument-panel-troubleshooting/

If I had to make a choice, I would use a sender that registered E when there was still 1-2 gallons in the tank and may not get to F rather than read 1/8 when bone dry.

[Bob Gaines]

Thanks Bob for the info, I tested them how you mentioned and
thats how I came up with the differences in them, helped a
friend do the same on his car, we bend his tabs/stops and
that seemed to help his problem.

Don't neglect to try cleaning off the wrapped wire as not making good contact could cause the symptoms also.