Cameron38

iTrader: (2)

Make sure the new Sending Unit was put on in the correct orientation. I just replaced mine (my gas gauge would go to full after refueling and then drop to empty after using the first 1/8 tank). Now it works perfect.

t_g_farrell

iTrader: (1)

Theres normally a ground strap that goes from the attachment point of the last
muffler hangers to one of the bolts on the muffler. This gives you a good engine
relative ground. A lot of times it's gone missing or broken off. I would make sure
that ground is in place first.

1978

I have a 1982 and my service manual says the gas tank DOES NOT have to be removed.
It says if you remove the left rear tire and then the fuel tank cover you should be able to remove the sending unit.
It may be tight and the picture suggests that you may need to use a short screwdriver and be careful not to bend the unit during removal, but that beats having to drain and remove the whole tank.
I haven't tried it yet but I will post details if I do.

mazdaverx713b

iTrader: (91)

The FSM was written when these cars were new and everything came apart like butter. This is no longer the case and we must sometimes go above and beyond to perform a repair.

The issue is that the screws that hold the sending unit to the tank are likely rusty and easy to strip. Small vice grips are required at times and in extreme cases, a horizontal slit must be made in the head of the screw when the screw head strips. It's much easier to work with on the ground and I recommend removing the tank for sending unit replacement.

Ckforker

I definitely had to take my tank out, plus it's a great time to clean it up inside and out. Then you can also paint to help preserve it.

Glassman10

I find myself in the same boat. My '79 was stored for forty one years in climate/temp controlled garage. When I wound up with the car, it had 63K miles on it. I had the seals and the oil metering hoses replaced along with all other rubber hose and belts. I had the AC hoses replaced at Cold Hose in Florida and cleaned out the compressor. I take the car our on nice days for 40 mile or so outings and am amazed at how bad the fuel milage seems to be. I think it is getting about 17MPG or so. I have to put fuel in regularly since the sender on the tank doesn't work. I have read here that there are apparently three potential issues in fixing it, the first being whether the unit has a decent ground, the second being removing the sender unless cleaning up the ground works. The one I'd like to avoid is dropping the fuel tank. Sometimes it goes up half ways and drops to zero after about 4o miles, sometimes it doesn't go up at all. On a rare occasion, it went above half full. Do those sporadic variations suggest anything about whether it should be replaced - which I have not confronted in the parts issue, or is it just clean and reinstall, hold your breath and pray?

The AC works pretty well but it does seem to be quite the parasite when it comes to loss of power while it's on. Everything else works really well. I love the car but it's hard to get in and out.
Thanks

KansasCityREPU

iTrader: (9)

I just restored a 1979 gas tank. Had to professionally cleaned and recoated at an radiator shop. Not cheap but that did a fantastic job. They also brazed in a drain plug since the 1979/1980 did come with one. The fuel level sender was rusted in place. I blasted it and got it working again and validated the ohm readings for empty/mid/full. I don't remember there being a ground on the gas tank on the 1979. Could be wrong.

mwpayne

As far as the sender, my 79 was the same. Take driver side rear wheel off and you can see how to remove the sender. First though use a meter to make sure 12v and good ground is there with key on.
If so, I took mine out and put it in a pail of evaporust a few days.
Works like new now. Worst case check with Riggs Vintage Rotary and get another. Probably have to rust treat it as well though.