I replaced the factory 19gal tank with a 38gal tank from LMC truck. The kit came with a copper pipe you weld on to the existing sending unit after you cut it to extend the pick up. It also comes up a crimp on wire extension that goes on the wire that runs down the sending unit in the gas tank. I reassembled the whole thing and the fuel gauge stopped working so I took it all apart again and noticed that the ****ty crimp on wire that the kit came with had already fallen off. So I pulled it off and properly soldered it on with heat shrink and everything then took the sending unit and hooked it up how it would be once installed and checked the gauge to see if it was working which it was, so I once again reassembled it and it still doesn't work. I tested the wire coming out of the sending unit with a ohm meter and it was reading around 80. I also grounded out the sending unit to test the fuel gauge and it pegged full so I know it's working but I can't figure out why it's not reading the file level. Any help would be appreciated.

 

It reads fine when the sender isnt in the tank but doesnt read when in the tank sounds like to me you dont have enough fuel in the tank to read.

 

That's what I thought but I put in 15 gallons today and it still reads empty

 

Is the sender grounded to the frame? Either through a jumper or through whatever clamps it into the tank. Is the tank grounded or isolated with rubber strips?

Michael

 

The sender has a wire that grounds on the frame and the tank straps have rubber on them at the point where they contact the tank itself

 

Sounds like you've got the low hanging fruit.

T'wer me, I'd lay the sending unit on its side outside of the tank so I could move it around while watching the gauge. Remember that the gauge is slow to respond. With it out of the tank, you do have the whole fuel vapor/spark issue so I'd put something over the hole. For those playing along at home, there is no danger of a spark causing problems when the sender is installed as the air/fuel ratio is way out of the flammable range. In open air, all bets are off.

Michael

 

Found the problem. After I dropped the tank again and pulled the sending unit out and hooked it back up to the factory wireing harness, I found out the the connection between the wire that comes out of the sending unit and the factory connector that goes into the harness was broken. So I cut them off and soldered on a new connection it worked fine. Hopefully that was the last time I have to take that tank out. Thanks for the help

 

Cool, glad it something easy and cheap to fix.

Michael

 

Quick question, does the tank have to make connection with the frame of the truck to ground or should the tank stay in between the rubber and the truck so it doesn't ground?

 

There is a ground strap that is bolted to the frame that is part of the wiring connector that plugs onto the fuel sending unit.

The tank does NOT need to make any additional ground connection.
The insulators are there so that the metal straps do not rub through or rust through your gas tank.