Fuel Gauge info

[Charles]

1987 B2 2.9L
Thought I had this thing beat, but I'm still having issues with my fuel gauge.


It registers very little, meaning, if I put in what I think is half a tank, it moves up very little from "E".

I'm pretty sure its the sending unit/pump/float unit or whatever it's called that's in the tank, but is there a way to troubleshoot this with a meter before dropping the tank (again!). I've been doing some reading and get an idea that these things are common to go bad, and all it is is a wiper or something attached to the float and the resistance changes depending on the float position.

can I tap into those wires and check it? what are the wires going into the tanks? Any thing else I can check before dropping the tank.

 

[BRUTUS_T_HOG]

run it almost out of gas and remove the tank. it makes it very easy to test the sending unit.

you can tap into the wire and watch the resistance change while you add gas, but you won't get to move it up and down.

another option you should do it remove the wire and groung it out, the fuel gauge should read pegged full. if not the gauge is bad.

i don't know the wire color or i could tell you

 

[Charles]

run it almost out of gas and remove the tank. it makes it very easy to test the sending unit.

you can tap into the wire and watch the resistance change while you add gas, but you won't get to move it up and down.

another option you should do it remove the wire and groung it out, the fuel gauge should read pegged full. if not the gauge is bad.

i don't know the wire color or i could tell you

thanks for the response. Would that wire of info about it be in the Haynes manual?

I was thinking the same thing after reading several post and wanted to try it but didn't know which one to try.

Anyone ever troubleshooting wiring with a meter and not wanting to cut the wire or strip the insulation, these things work great:

 

[BRUTUS_T_HOG]

i love those things. don't forget to reseal the wire afterwards.

a haynes manual might show it. someone on here probably knows though.

a couple times i've gone to the library and copied pages from their auto repair manuals

 

[redxlt]

go to ebscohost.com they have wiring diagrams . you just select what you need. login in is: tech password is :tech

 

[unoleisu]

Befor you drop the tank.....
I would start by checking your ground. The engine to body ground first, and then the black wire at the fuel gage sender. It is G200, which is the main black wire ground under your dash near the steering column (driver's side of it, I believe). The Y/W wire at the sender goes to the gage.
I'd also pull the wire connector at the tank sender, and check the connectors for corrosion, clean very well with fine sand paper if needed, and use a little dia- electric grease to help prevent corrosion in the future. (I completely dis-assembled both halves by pulling the pins, and cleaned)
Also, the fuel, coolant temp., and oil pressure gage (if you have it, mine is just a light) are fed by the Instrument Voltage Regulator. It feeds them 5 volts, and if you are noticing any issues with the other gages, it could be this.

To check the gage callibration you need one each 10 ohm (high) and 73 ohm (low) resistors. Connect each, one at a time in series with the Y/W wire, and sender unit connection. If the gage tests fine, the sending unit is bad. If gage tests out of calibration, it may be the gage.

And..... you would REALLY benifit from installing an access door thru the inside (middle of the cargo area) there are several writeups about it, with pics. I did it and am very happy I did.
Good luck, hope this helped!