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After Replacing the Temp Sending Unit, My Fuel Gauge Sort of Works Now?


TheLuckyMakeIt

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Hi All,

I am new to this forum but have been using the wealth of information found here to help fix up my 1991 Ford Ranger. Thank you all for helping me out so far!
So, my truck has a few problems, one of them being that the temperature gauge and fuel gauge do not work. Yesterday, I replaced the temperature sending unit after doing a flush and the temperature gauge now works. The fuel gauge now moves too though which is puzzling me. It was originally stuck on empty so I figured that I had a punctured float in the gas tank. When I start the truck it goes all the way back to empty, but when the truck is off, it'll read around a quarter of a tank, which is probably correct. I haven't tried putting more fuel in it to see if it is actually accurate or not. I'm a bit confused as to how the temperature sending unit would effect this. Also, when I tested the sending unit and grounded the wire to the engine, the fuel gauge moved as well. This makes me think it could be an electrical issue rather than a punctured float. What do you guys think?
 


RonD

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Yes it reads like you have a poor or bad Ground for the fuel tank sending unit, it works similar to the temp gauge, in that both use Ground as reference.

You don't say what engine you have but shouldn't matter
If you look here: http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_Enginecontrols4_0_3_0_1of3.JPG

Lower left/center is the wiring colors for the sending unit in the tank
Yellow wire goes to the gauge in dash
Orange wire is the Ground for sender

Orange wire "can be" spliced to Fuel Pumps Black wire on some harness' but usually they run separately to inside the cab, passenger footwell near Inertia switch.

If you have an OHM meter you can connected it to the Yellow and Orange wires going to sender in the tank.
EMPTY = 16 Ohms, FULL =158 Ohms

If you rock the truck the float will move up and down as the fuel moves and you will see the OHMs change.

Also test Orange wire to Frame Ground, should be 0 Ohms if not reGround Orange wire


Other thing to check is the Ground strap from Engine to the Firewall, that is the main ground for cab instruments.
There should be/will be, a ground strap from the head to the firewall, it is often left hanging after engine work, opps.
If it isn't hooked up or can't be found then ADD ONE.
Can't have too many Grounds

And from your description it seems the fuel gauge is using temp sender ground because strap is not connected
 
Last edited:

TheLuckyMakeIt

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Thanks so much for the info. The ground strap is there, I see it coming from the drivers side down into the engine (can't see where it goes but a light tug shows that it is definitely connected to something). I just hope its connected to the right spots on either end.

I'm going to take a look at the wires tomorrow and see if I can figure anything out. Sort of wish it was a punctured float at this point....
 

RonD

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Well it could also be the Anti-slosh module on the back of the dash

Google: ford ranger anti slosh module
 
Mhfco6

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This is is some good info. My fuel gauge and temp gauge don't work either. Temp gauge reads just above cold after driving the truck for a while and fuel gauge reads dead empty when truck is running. When truck is off it slowly moves up to about 1/4 tank. I will check the yellow and orange wires. I saw the ground strap in the engine bay. It sat in the upper left hand corner facing the truck. One side was connected, the other was not. The strap was only about 6"-7" long. I also tried the anti-slosh module bypass and that did not help my fuel gauge at all. It just made my speedometer fluctuate and read about 5 mph faster since I put it all back together. I will repost with results. Thanks for the info fellas!
 
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