Fuel gauge says empty tank, but yet "working"

[wegngis]

My gauge isn't displaying properly, it shows the tank as empty all the time. But it will rise from 'off' to 'empty' with the key on. If I unplug it from the sending unit, I get no movement. From what I can gather, the fuel gauge is supposed to read empty at ~73ohms, and full around 10ohms. If I stick a meter on the sending unit, it reads about 73ohms, and that's consistent with an empty tank. So, I think the gauge is OK, it's the sending unit. Agreed? I did read a little bit about using a 9v battery on the gauge leads to test for movement.


A little background: I did have to pull the sending unit from the tank to get the tank repaired, but it still worked after that. I'm wondering if I killed it accidentally, or maybe it was just it's time to go. I'd really like to not pull that sending unit as it's a real bear with the tank installed, and it's a real bear to pull the tank. Maybe there's a fix otherwise? Banging on the tank perhaps? %)

 

[70_Steve]

My gauge isn't displaying properly, it shows the tank as empty all the time. But it will rise from 'off' to 'empty' with the key on. If I unplug it from the sending unit, I get no movement. From what I can gather, the fuel gauge is supposed to read empty at ~73ohms, and full around 10ohms. If I stick a meter on the sending unit, it reads about 73ohms, and that's consistent with an empty tank. So, I think the gauge is OK, it's the sending unit. Agreed? I did read a little bit about using a 9v battery on the gauge leads to test for movement.


A little background: I did have to pull the sending unit from the tank to get the tank repaired, but it still worked after that. I'm wondering if I killed it accidentally, or maybe it was just it's time to go. I'd really like to not pull that sending unit as it's a real bear with the tank installed, and it's a real bear to pull the tank. Maybe there's a fix otherwise? Banging on the tank perhaps? %)

Float is missing or filled with gas.

 

[demesauce]

Agreed. The float is full of gas or missing. The float can develop a small crack over time and slowly fill with gas, making the "float" act more like an anchor. Take to the sending unit and either repair the float, or better yet, buy a new one for a couple bucks

 

[wegngis]

I didn't think about the fact that it could have developed a micro-crack and filled with gas. Bummer. I know it's in there, but I suppose it could have fallen off. Either way, no workie.

 

[dmill33]

piggy backing

Sorry to piggy back on your thread, but since the fuel gauge is being discussed I thought I would ask a question here instead of starting new thread.
I replaced my stock tank with a 23 gallon and ever since the gauge shows empty after the stock amount is used. Any ideas?

 

[wegngis]

You can do what I did, check the resistance on the sending unit. Does the needle move just a little, or is it completely immobile when you turn ignition on?

 

[dmill33]

It works fine when I fill up. It shows empty when I burn up about 12-13 gallons, I know there is another 10 gallons in there though.

 

[demesauce]

dmill33, I had a similar issue. The stock sender wasn't designed for the extra capacity fuel tank. The float arm can't articulate from full to empty on the bigger tanks. I had to bend the metal float arm connects the sender to the float so it could accommodate the different shape of the tank. My still isn't perfect, but much better that it was. I think a longer float arm would make it work better too. What tank do you have?

wegngis, if you take the sender out, check resistance again, or hook it up to the wires after removal and physically move the float up and down to see if it is still good. New sending units are fairly cheap, but I think I bought the float separately on eBay

 

[demesauce]

Under $7 shipped...

http://www.ebay.com/itm/Ford-Mercur...Parts_Accessories&hash=item2edd2a4853&vxp=mtr

 

[wegngis]

wegngis, if you take the sender out, check resistance again, or hook it up to the wires after removal and physically move the float up and down to see if it is still good. New sending units are fairly cheap, but I think I bought the float separately on eBay

Good idea, but the trick will be running the tank low enough on gas so it doesn't come spilling out when I loosen the ring, but not getting stranded. Not looking forward to this one. Maybe it will just magically start working again...

 

[dmill33]

Thanks for the info. I too believe that the float/arm is the culprit.

 

[Explorer]

Short the wire at the sending unit to ground and gauge should read full. Verifying what you already suspect and gauge is good.

 

[DuctTape]

Good idea, but the trick will be running the tank low enough on gas so it doesn't come spilling out when I loosen the ring, but not getting stranded. Not looking forward to this one. Maybe it will just magically start working again...

You can siphon from the sending unit to empty the tank. Put a length of hose on the sending unit, other end in a gas can, pinch or plug the hose when gas can gets full, empty gas can in teenage daughter's tank, rinse repeat.

Doesn't take much to get it going, ask me how I know.

 

[wegngis]

You can siphon from the sending unit to empty the tank. Put a length of hose on the sending unit, other end in a gas can, pinch or plug the hose when gas can gets full, empty gas can in teenage daughter's tank, rinse repeat.

Doesn't take much to get it going, ask me how I know.

Wow, of course. I'm being dense today, thanks for pointing that part out. I'm so focused on the diagnosis/fix that the simplest part escaped me. %)

 

[DuctTape]

Wow, of course. I'm being dense today, thanks for pointing that part out. I'm so focused on the diagnosis/fix that the simplest part escaped me. %)

Happens to me all the time! Best part about these forums.