Fuel Sending Unit

[rdhack]

I was thinking of replacing my fuel sending unit. 1982 GMC K1500/ Carburetor. My electrical connection has 3 terminals -one which is ground. Every fuel sending unit I have seen so far only has one terminal with a ground wire to attach to the frame. My question is which one of the other two terminals would I use?

[hatzie]

That sounds like you have a diesel sender.  The extra terminals are for the Water In Fuel sensor.  If it's original 1982 it probably has four pipes too...  Supply, return, vent, drain.
If it's working just leave it alone.

This style of Diesel sender is not available.  You can replace the original sender with a three pipe gasoline sender.  The ground will run from the locking ring to the frame.
Usually the sender wire is Tan, or Blue...  Download the 1982 GM wiring diagrams from the "my Bucket" manuals link in my signature...

[rdhack]

Yes that makes perfect sense! This truck was originally a Diesel and then converted to gas by a previous owner. So all I really need to do is use the pink wire from the selector valve (it had duel tanks as well) I have traced pink/pink-whitestrip to the selector valve and a soled pink sandwiched in between which go to the cab.

NOW the next question and Im betting you can answer it. I did a resistance test across the unit and it reads open across either 2 terminals I choose. Does that reading mean this sending unit is bad?Should it read some type of resistance between pink & ground? If it is good?

OH Thanks!

[hatzie]

Well...
90Ω = Full.
0Ω = Empty.

If you're really reading from the sender signal wire to the ground and there's more than 4-5 gallons in the tank you should be reading something on your meter.

Here's a 1982 sender without the vent line...  http://www.dieselplace.com/forum/4400850-post29.html

You can test the gauge by grounding the valve to gauge wire on terminal B of the valve plug.  The gauge should drop to zero.