Hi all, just replaced my tank on my 72 Skylark and also replaced sending unit. Checked sending unit prior to installing in tank and all was normal with gauge in dash.( full with float up, empty when down etc.) Installed tank and put in 10 gallons of gas and no change on gauge on dash(sitting at empty). I am certain wire is still connected since gauge is reading empty and not way past full. I assume it takes some gas for it to begin to register, like maybe a gallon or two??, but figure I should be reading something with that much in it. Before I drop the tank to see if float is bound up (or has a hole in it) I figured I would check here for ideas first. Thanks in advance!
Unplug the connector for the tan wire in the trunk and take an ohm reading to see what the sender is saying
If the car is drivable, go drive it. Hit some bumps and make some turns. It will probably start working.
Right, that's because the curcuit was open. The side thst goes to the tank should have an ohm reading.
That's low. I'm pretty sure that it should be around 45, assuming that 10 gallons gives you 1/2 tank. I believe that the sending unit is 0-90 ohms. If that's the case, either the sending unit is bad or the float is stuck. Before you remove the tank, hit the bottom with a rubber mallet. If the tank is nice and painted, put a block of wood or plywood on the tank and hit that. At any rate, you shouldn't need to hit it hard enough to damage the tank.
In case I have an incompatible replacement sending unit I went with this one. Says compatible but wondering now. Spectra Classic Fuel Tank Sending Unit FG91D https://a.co/d/4aZHhRQ
That unit looks correct, reads 3 ohms empty, 90 ohms full. So at 7 ohms, it will read very close to E. Read post 9 before dropping tank.
No luck getting any response from the unit, looks like a tank drop is in order. Not sure how it tested good prior to install and now doesn't work. Possible hole in the float perhaps I guess.
It appears as though the baffle in my new tank is interfering with the float. I am using this tank from Dorman. https://www.dormanproducts.com/p-81154-576-069.aspx I bent the float rod on my sending unit to make is shorter(to keep it closer to pickup tube) and this allows it to work, however now knowing if it’s accurate is the tricky part. I put around 6 gallons back in before it moved my gauge. I tried to get the empty float level back to as close as it was before I bent the rod. Maybe should have also got a Dorman sending unit to avoid all this ( I have the Spectra FG91D)). The baffle in this new tank was about a 1/2” closer to the sending unit opening than the original.
I used the spectra sender and it hit the underside of the trunk pan. When I put the tank up, the tank was teeter tottering against the sender
