1. The idea of the green wire is to ground the sender metal to a good chassis ground. Which it seems you have done. There is no reason to worry about grounding the tank.
2. Your terminal crimps are sketchy looking and the center tap terminal should be away from the flange and bent up a little. Turn the red wire terminal around so that wire (insulation) comes straight into, and inside of, terminal sleeve.
3. The 5 screw pattern on the sender only allows sender to be mounted one way. Don't know how you are orienting the sender two different ways.
4. We have asked you to explain things several times carefully and completely because this gas gauge stuff is hard to catch. We see this question a 100 times a year. We are not there and trying to see what's up. So we keep having to ask a bunch of question about what you did and how you wired and how you tested.
So now I will ask what everyone wants to know.
1. One time you test with tank mounted in truck and sender mounted in tank and gauge mounted in dash, right?
2. Then you test with tank mounted in truck, sender loose and gauge in dash, right?
3. Both tests, wires are as we see. Wires not disconnected from sender or gauge or ground, just lift sender out, right?
4. When all are mounted properly, gauge reads near empty with lots of gas in tank. Right?
5. When sender is held outside tank with all wire still hooked up, gauge shows correctly on gauge when arm operated by hand, right?
6. You said..... "i noticed when I'm tightening the screws I get no reading at all." I asked you what screws you are talking about in that sentence, YOU DID NOT ANSWER. We are looking for clues here so help us out.
7. You said....."When not installed in tank I hook up signal wire and tightened nut then I place the ground wire on the top of unit". What does "place the ground wire on top of the unit mean? How are you attaching the ground wire to the "unit" when it's hand held ????????....and let's don't call things "units". I assume you mean sender.
I am focusing on this being a clue. Like good ground when sender is out and bad ground when sender is in. So need to know how you are grounding the green wire when sender is out verses installed on tank and putting terminal under screw head and tightening the screw down on tank sheet metal. Be sure ground terminal is touching tank flange directly and not on top of a washer. The washer could be rusty or corroded or not conducting. Ground should still conducting thru the threads but you never know.
All we have is questions and your answers and your detailed explanations to go by. We know how it's wired, we know about ground. We are trying to catch a mistake or malfunction. please notice all questions and answer EACH ONE. We will get it solved that way. We have lots of experts here but the key is we need to visualize what exactly you are doing so we can suggest tests.
The whole problem with grounds of any kind is that the motor has rubber motor mounts, the body has rubber mounts, the tank has rubber pads, the bed has rubber sometimes. The gauge frame needs to be grounded. the needle sticks, the sender has a gasket. The sender ground relies on screw threads. Light housings have gaskets. Rust, corrosion, grease and paint interfere with grounding........So all those braided ground straps on our trucks are real important as well as clean, bare metal ground spots.
