How to check fuel sending unit?
 

Hey Guys!

This weekend my son and I are going to drop the fuel tank and replace all fuel lines and filter all the way to the fuel pump. (we're chasing a fuel flow problem--more on that later after I have more facts). But my question is--how would you check the fuel sending unit out of the tank? His fuel guage doesn't work and I'd like to see whether that is the problem or not before we put all of this back together. The truck sat for a long time with a little fuel in it (about 4 yrs. says PO) and I think the sending unit may have gotten stuck or something. Anyway, I'll be dropping the tank, so I thought I'd check it out. Any procedure for this? His truck is an '85 4x4 22r. Thanks to any and all for help!

Chuck

well if you pull the sender out and move it the gauge should move up and down, if not then the sender is prob bad. but to test the sender start with the plunger down (like the tank is empty) and test the ohms between the terminals, then move it up (tank full) and ohm test again, im not sure if its more ohms with less fuel or the other way around but it should steadily go from one extreme to the other...... i would say 90% of the time its the sender

Sender electrical specs on the web page below:
- http://www.4crawler.com/4x4/4R_TechI...tml#Electrical

if you have a multi-meter(YOU SHOULD, IF YOU DONT GO BUY ONE. NOW) you can measure the resistance between a couple points.

separate the plug that goes to the sender and figure out witch contacts go to the wires: yellow with a black stripe and yellow with a red stripe. These wires will have a resistance between them between 3 and 110 ohms. If the sender is bad it will read 0 ohms.

Thanks guys for the replies! Well, we got the fuel tank out and there was quite a bit of rust in the bottom. We cleaned that out. The sending unit was indeed stuck in place from sitting so long. I had it out of the tank and cleaned it off. I then hooked it back up along with a ground wire to the body and it worked!:) Now, I was thinking of sloshing around some sealer for the fuel tank before we put it back in, so we don't have the continuing rust clogging the fuel filter problem. Anyone done that? Any suggestions? Thanks again!

Chuck