fuel gauges!!

i know, i know, it's been tackled tons of times... but it's just not working for me. last weekend i picked up two sending untis and two speedos in the hopes of getting at least one of them to work. unfortunately, the tech at the monsterslayer website and the site which basically quotes that one word for word are of no help. i seem to have bought a newer style speedo with only two terminals ont he back connected by a resistor (no help troubleshooting those). i did the search and it seems as though tgregg was having the same issue a couple of months ago, but i didn't find the solution.

soo, here's what i've done so far. i checked the sending units i bought, along with the old sending unit and here's what i found.

new #1 measures 120 ohms empty, 20 ohms full
new #2 measures 110 ohms empty, 20 ohms full
old unit measures 75 ohms empty, 11 ohms full

that's great, both new units measure to high, and the original one checks out. but when i connect them to the gauge it peggs out at full. it is, however, still going in the right direction (moving the sending unit to full sends the gauge to a "more full" position). soo, that means i got to check the gauges out...

like i mentioned earlier, the gauge has two terminals on the back connected by a 150 ohm resistor, which explains why it's going to read full all the time. the voltage drop across there is always going to be greater than 8 volts, which just happens to be where full is... ohh the fun.

anyone ever troubleshot this and know what resistors need to be placed where?? i know the 150 needs to go down and/or another resistor added before the sending unit gets grounded, but i don't know what size. i've got a variable resistance pot coming to me next week, but it sure would feel good to have a working gas gauge, and an installed gas tank, before then...

and if you got this far, thanks for reading my little rant/cry for help.

 

I bought 2 new speedo assemblys and a new sending unit. One gauge wouldn't work at all and the other runs down from full to empty but the tank is still half full. I have two tanks, the stock under the seat which does the half tank thing and a big tank under in back that has no sending unit (at least I don't think so). So I run the rear out then switch to the under seat and go to empty, then I have 5 gallons to fuel up. Not perfect, but it works.

 

Gregg your rear tank if it is a jeep tank has to have a sending unit in it as that is the plug for the top of the tank. The fuel line coming out of the tank is the top of the sending unit, there should be a single white wire attached to the unit.

 

Thanks, It looks to me like a homemade tank. I am just hooking it up as I received my electronic fuel valve yesterday. Someday I'll drop it down and have a look. In the meantime I'll look for a white wire while I am under there.
Have a great T-Day!!
Gregg