Yet another problem with my 89...

The fuel gauge stays on E about 95% of the time. Occasionally it will read about 1/4 of a tank... I've been going by the seat of my pants, filling up when I thought I needed to... Then I saw this thread (https://www.ford-trucks.com/forums/s...ad.php?t=33311) and decided to try & figure out what the deal was...

I checked my sending unit and gauge last night & here's what I found... I had a 4 wire connector with a Brn/Wht, Orange, Yel/Blu, and Blk.

Unplugging that connector pegged the gauge to F.

I determined that the Yel/Blu was the positive lead for the gauge/sender circuit, and the Blk was the negative lead.

I measured 8 Volts between these two leads.

When I shorted the Yel/Blu (positive) 8 volt wire to the frame, my wife said that the fuel guauge would climb down towards E. The electronics in the gauge seemed to be working correctly because it moved slowly.

Seeing that the gauge seemed to be ok, I checked the resistance across the leads that went to the sending unit. Initially, I read 15.6 Ohms. I added about 1/2 gallon of gas and checked it again. The 2nd time, I read about 15.9 Ohms.

Questions:
I thought that 5 volts was what was used for senders - why did I get 8?
Would getting 8 volts suggest that I had a bad voltage regulator or something?
Is there a chart somewhere for %fill vs. resistance on the fuel level sender?
Any idea on why my gauge doesn't work?

Note: I have dual tanks but the front is junk so it doesn't get used. This is all in the rear...

 

Sorry, wrong forum...