This car has been stored outside for the last 3 years with a full tank of gas and I start it every month or so. Previously the fuel gauge would show almost full but now it's reading empty with the light on. I pulled the sender connector and put a jumper wire across the terminals and the gauge went to full so I know its the sender. I did run a hose down the fuel filler to make sure it has gas and it does. So it looks like the sender is not reading correctly. Can the unit be taken apart and cleaned? I assume it's just a typical float arm rubbing on a resitance wire type thing.

I had the same problem eith an old caddy I had. The gas turns into something like a varnish. You need to clean the tank. It will surely gum up the filter and anything else in it's way. If you can drain the tank and rinse it with a tank cleaner made for that purpose, you may be able to get away without removing it. Of course be careful not to make any sparks. I ended up removing the tank, taking out the sending unit and cleaning it. I washed the tank with detergent and water, but of course dried it thoroughly before putting it back together.

I have no connection with the manufacturer.

Try a couple of tanks with this added...it should clear up your "Varnish"
problem.(Save all your hard labor and Cash for when you really need it!)

How ever it is still possible that you have Mechanical difficulties with the
sending unit...You may need to take it out and clean/repair it.Be very,Very
careful with the tiny little guide wires and connections inside the Tube!

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'84 300SD sold
124.128

There is nothing wrong with the gas, it's the fuel sender. I removed it out of the tank and took it apart. The float rides up and down on a pole that is in the center of it and there are 2 pairs of contacts on each side of the float that touch 2 resistance wires. Looks like those contacts have lost tension and don't touch the resistance wires well enough. Has anyone tried to take the float apart? Maybe you can bend the contacts enough to make it work again.

Have you played around with the Fuel Sensor with a Multimeter?
The FSM, I Believe has resistance values published.
('Just trying for Empirical evidence that the contacts on the float are the
problem.)

I cannot remember what the sliding contacts on the float look like...Do they
look bendable?
I'd be real tempted to try...

'You know what, the Moderator, a Pro will know...Ask.

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__________________
'84 300SD sold
124.128

I was able to take the float apart and bend the contacts tighter. It seems to work fine now.