Ckforker

Before I get an unwanted surprise, does the fuel level need to be low to take out the sending unit? I overfilled the tank thinking there was a problem with the filler neck before finding out the gauge or sending unit is not working properly.

Also I've searched the sending unit, and mixed answers on if it is on the left (I think this is correct), or on the right. Seeing both sides on different sites.

Hopefully it just needs cleaning, but see some for sale for pretty good prices if I need a new one. I would not think the gauge is inaccurate. The gauge maxes out at half tank, but does drop down to empty correctly.
Thanks

t_g_farrell

iTrader: (1)

The gauge being at half when full probably indicated a poor ground either from the sender to the tank (most likely) or the rear chassis to the engine (woven wire attaches from the rear of the muffler to the bolts for muffler mount onto chassis. Make sure thats there and good before digging into the sender


The sender itself can be rejuvenated pretty easily, maybe with out removing it. One test is to just jump from the center of the sender using a probe and ground it to the bolts of the sender. If that makes the needle move up to full on the gauge you can fix this without removing the sender.

Sender is on the drivers side of the car behind the rear wheel under a plastic shield which you need to remove. Be prepared for rusty little bolts holding that plastic cover on. Easy to break off and such. The sender is pain to get off while the tank is in the car but it can be done. The little bolts that hold it in break off easily but once the sender is out they are easy to back out of the take mount if a stub is still sticking up. Not sure if a full tank will be an issue when its removed. Since you have an FB I would drain it about 4 or 5 gallons down before.

Ckforker

Thanks Tim, the ground strap is good, I cleaned of the grounds on the car I could find last year. I'll pull the inner fender plastic and check those wires before attempting the sender.

Given the car has been sitting outside for the past 8 months while my shop is being built, it probably is an electrical connection.

Good excuse to burn some fuel over the next couple days!

Holdfast

My gauge was doing the same thing. I just went through all the bs of checking the wires. These things are just worn out from the float going up and down for the last 34 years. Just buy a new sender before you cant find any new ones. After i replaced it. I took the cover off of the old sending unit where the arm is. There is a small coil that the arm touches and it had completely worn the wires through. It also seem like the float was absorbing fuel. Which would cause a inaccurate fuel level reading. But i would drain the tank before doing it. Gas sitting for 8months might not be any good anyway. Absorbs moisture.

Ckforker

I ordered one last night, hopefully to just have as a spare. Gonna go through the wiring today first.

I misspoke, I've been driving the car all winter, but it's just not been garaged. I live on the coast and the salt air has not been kind to my car. Fortunately it will be in the new shop starting next month.

mazdaverx713b

iTrader: (91)

There is likely corrosion on the sender pins and contact points. You can do a resistance test on your sender once its out, but it likely needs replaced. You will want to drain the tank and remove the tank before replacing the sender. Ensure the female pins in the harness are clean as well before installing the gas tank. .

Ckforker

Corrosion wins!
The sending unit is rusted to the tank, so I just soldered all the leads to the sender for now. It works, but will need to drop the tank to remove rust. Mazda protected the unit enough to keep under coating away, but not water from the tires, nice design...

I'm just going to enjoy it as is till the weather gets too hot to enjoy the car.

I've now got a huge list of items to fix/replace:
Sending unit
Gas tank/ fuel lines
Rear end rebuild- all bushings, fix leak
New clutch + seals
New u-joints
New exhaust
Rear brakes

I'm sure there's more. Glad I'm retired, this is gonna take a long time.... May have to go back to work just to buy parts though!

mazdaverx713b

iTrader: (91)

Glad you got it sorted out for now. Corrosion builds in the connector quite frequently, causing high resistance and a non functioning gauge. Keep us updated and let us know if you need any more advice.