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Put new original style gas tank on 1954 truck. Order new sending unit that works with stock gauge that I know is good. Hooked it up on outside of tank and moved float and it work good. Installed in tank and now gauge dose not move at all. I have taken off numerous times with same results. Ican tell float is not hitting on side of tank when I drop it in just cannot figure out why it is not reading. I have about a 1/2 a tank of gas in it but needle does not move when installed only when sending unit is removed and moved will it work.
Probably a grounding issue on the sender. This is easily remedies by running a distinct ground wire to a mounting screw of the sending unit.
After some thought if it works outside the tank then it must be grounded, right ? I have exactly the same problem but in my case it is aftermarket plastic fuel injected tank that has a four wire plug that includes the ground, how can it work out of the tank, but not in the tank. Sorry for hi-jack.
Replacement steel tank or plastic tank, I've done both types on various vehicles, and whether it calls for it or not, I always run a dedicated ground wire from the the sender housing (lug on one of the mounting bolts of the sender to the frame (for the truck) or unibody (for various cars I've worked on). Saves a lot of frustration in the end, never had one that didn't work after I installed it with the ground.
For whatever the reason (cheaper metal, slight coating on the metal, etc.) the after market sending units do not ground as well as the original ones.
Some sending units come with screws that attach to the tank and these screws came with a silicone type sealant o ring on it. I had to exchange that screw to one without to secure the ground cable.
Some sending units come with screws that attach to the tank and these screws came with a silicone type sealant o ring on it. I had to exchange that screw to one without to secure the ground cable.
It is going to be hard to externally gourd this sucker !