Fuel gauge sending unit

[Astre-mutt]

Pulled the gas tank today. Found a big hole in the connection between the fuel pump, and the fuel line. Fix the problem without removing any wires, or connections. Now my gas gauge points at the 3 o'clock position, and doesn't move. What do I need to do to fix the problem?

[spyder_xlch]

You must have disturbed a connection somewhere or just discovered a bad wire. You have an electric in tank pump right? Was this hole inside the tank requiring you to remove the pump from the tank? You could have broken a wire too.

[Astre-mutt]

Yes Matt, it is a in tank fuel pump. I know these in tank wires are prone to cracking, and breaking. So I was very careful not to even move any wires. The rubber connection on the pump had swelled up like foam rubber, and there was a hole that I could almost stick my pinkie finger through. The sending unit arm got flipped around a bunch of times when replacing the rubber connection. Nothing else was disturbed. I even cleaned the wire connections at the top of the tank.

[spyder_xlch]

The arm that holds the float got spun around? Did it actually spin around or just flop around? Might have lost contact.

[Astre-mutt]

Just up and down. There is a stop at the empty level of the sending unit, but there doesn't seem to be a stop for full. I guess it would just hit the top of the tank when it's in the tank.

I had a similar problem in my Suburban when I change the pump in it. It still worked after wards, but it didn't read the right level.

I guess I'm doing something to the unit when I let the arm move around. I'm I just ignorant, because I've never knew you could hurt the sending units like this.

[cosvega76]

Make sure you have a good ground connection. GM fuel gauges read way past full if either the feed or ground connection is bad between the gauge and the sender.

Chuck

[spyder_xlch]

Just out of curiuosity did you change the pump only in the Suburban or the whole unit?

[Astre-mutt]

Matt, I only changed the fuel pump in the Suburban, but after I re-installed that bitch (40 Gal tank) back in place it still didn't work. I was tired of messing with it, so I had a shop redo it. I didn't know if they, or I did something to it. It still works, just not close to the right amounts.

The Astre fuel gauge doesnt move at all. Just stuck at the 3 o'clock position. Way past full. The car had a 1/8th of a tank of gas when I pulled it. Reinstalled it empty, and turned pump on to check if the pump was running. Then put 1 Gal. in it to get to the gas station. That's when I notice the problem. Put about 5 Gal. in at station, no change.

[spyder_xlch]

The question about the Suburban is alittle off topic but I was curious because alot of customers say their guage seems to read different after a fuel pump change.
As far as the Astre, if it's reading way past full wouldn't that mean a pinched wire? Meaning no resistance. I'm trying to think now. The sending unit works off of resistance but I can't remember is less resistance is full and more resistance is empty or if it's the other way.

[Astre-mutt]

Well I was hoping I did something that would have a easy fix. Looks like I'll have to drop the tank again, which is kind of a pain in my car. The previous owner put an exhaust pipe right under the tank. I still have one chance. I have a new speedo lens coming soon. I'll see if I can get lucky, and just move the gauge needle back. (probably won't be that lucky)

Are the sending units still available?

[Astre-mutt]

Thanks for the help guys. Looks like it was a pinched wire, maybe. Was going to pull tank this weekend, but thought I would try to check outside wires first. So I loosen the tank straps to see if I could find if a wire was pinched or not. Could not find anything wrong, so I checked the fuel gauge with the tank loose. No change with the gauge, still read way past full. It looked like I would have to drop the tank after all. So I tighten the straps back up, and pushed the wires back in place. Jumped in to the car to get something to eat, and low and behold the gauge was working. It even reads the right amount. Some time it's better to be lucky then good.

[clintjohns]

yeah i got the same problem. WONDERING HOW YOU READ A SENDING UNIT TO TELL IF IT IS WORKING OR NOT. i KNOW IT HAVE TO HAVE A HOT/POWER BUT DOES IT PUT THE POWER FROM THE ELECT. PUMP. OR DOES IT REQUIRE IT'S OWN SEPERATE HOT WIRE AND WHERE IS THE WIRE THAT SENDS THE INFO TO THE GAUGE??

[SunbirdMan]

Tan is the sending unit-.....dark blue is the fuel pump. The sending unit gets its power thru the guage. If you can get to the wires back there, either under the car or in the trunk, you could stick a fine sewing needle thru the insulation on the tan wire and put a volt meter up to it to see it it has current while the car runs. If it does I would think there is a problem with the sending unit. Now for the disclaimer: that's what I would do if it were my car but that doesn't mean I know what I'm talking about.

[Astre-mutt]

I got lucky on mine. I ended up loosening the tank straps, and moving the wires around. When I checked the gauge it was working find. I hadn't had any problems since.

I afraid I have to disagree with SunbirdMan. The sending unit is a ground system. To check the sending unit you use a Ohm Meter. On my car there is a wire plug connection about a foot & a half from the tank. You can check the sending unit from there. Not 100% sure the best way to check that the sending unit is working perfect or not. There should be someone more knowledge here that can help you with the details. (Matt?)

[SunbirdMan]

Scott, actually I think we are in agreement. The juice comes from the guage and the sending unit provides a variable resister to ground. But if the sending unit is working right it still needs to be verified that it is a live circuit. I've had a couple of adult beverages so I can't be sure.