74 Charger fuel gauge question?

[64fury74charger]

The fuel gauge was working intermittently with the old tank and sending unit, and the gauge would go almost all the way to full when I momentarily ground the sending unit wire. I have installed an Aeromotive fuel tank with efi pump and new sending unit along with Sniper efi and the gauge is dead.
I have verified good ground and also have the 5 volt reading at the tank wire. I verified the ohms reading on the new tank before installing and that’s good. Re-checked sending unit after install and was at 32 ohms at about 1/2 tank so that’s still working.
My question is if you have the 5 volt at the sender wire doesn’t that suggest that the gauge should be working as the voltage goes through the gauge correct??? Or am I missing something here.
I am really scratching my head and any help is greatly appreciated

 

[PurpleBeeper]

That all sounds legit. Something is weird

 

[64fury74charger]

That all sounds legit. Something is weird

That’s my problem with this situation. I verified that the gauge and wire to the tank were good and the sending unit was intermittent which is is not unusual. I verified the new sending unit that is in the new tank and that’s checking out good. I have one ground wire from the pump and sending unit going directly to the battery and an additional ground wire from the tank to the chassis.
I am not understanding how the 5 volt reference is there at the tank and yet when I ground that wire the needle doesn’t do anything ….. I haven’t touched anything in the dash at this point because I want to finish setting up the efi before I start tearing the dash apart. Any ideas or suggestions??

 

[Nacho-RT74]

My repro sender sometimes was loosing the reading. I had to kick up the tank and reading came back. Opened the sender and applied some pressure to the points tab for better contact against the rehostat. Fixed.

 

[64fury74charger]

My repro sender sometimes was loosing the reading. I had to kick up the tank and reading came back. Opened the sender and applied some pressure to the points tab for better contact against the rehostat. Fixed.

Thank you for your help Nacho, I am not expecting anything but average performance from the new sending unit because quality control isn’t in the program anymore. I tested the new sending unit when I first got the tank and everything was dry and moved it up and down with my ohm meter connecting between the sender and ground at the tank. Readings were looking good and I did it again after the install with the first 5 or so gallons in the tank. Again everything was reading in range and the new tank actually holds fuel ..

The 5 volt reference is there at the original sender wire at the tank, and the gauge is not moving at all .

W T F. There must be some little issue here that is just not showing up yet. .

 

[64fury74charger]

Am I reading this right, you have voltage going to the tank via the sender wire?

Yes you are reading this correctly and this is what is really making me scratch my head. I will be repeating myself here but previous to doing the tank / sniper efi install, I had taken the time to focus on the fuel gauge from the gauge to the tank so I would be relatively sure the only issue was the original warn out sender. I momentarily grounded the wire at the tank and the gauge moved almost immediately to the F and that should indicate that everything from the tank wire through the connector in the left kick panel and up to the voltage drop to 5 volt and the gauge are at least in working order.

I verified the new tank sending unit at several points before installing and again after installing and that ohms good. Any ideas or suggestions are sincerely appreciated because my head is really spinning on this one.