Thought I had this thing squared away. but it still reads off. showed quarter tank and it was just about empty.
ran out of gas last year too right around the block from my house
Any tips to getting this thing to register correctly?
I know there is a way to measure it but when you pull the sender out and measure empty /full do you just bend the arm a little for a certain reading?
what am I missing here?

 

Mine lies a bit too. Even when the tank is full it'll only ever read 3/4.. so when it starts getting near empty I imagine I have about a quarter tank. With the unit out of the tank, if I hold the float at it's max extension it only reads 3/4. So I have to question the wiring between the sending unit and the gauge. I'm thinking it's the wiring for the gauge cluster.. volt, fuel, coolant temp - all read slightly lower than reality. Example, I can meter the alternator and see 14 volts yet my gauge only ever shows 12. Temp is always an eighth versus a quarter, etc.

 

NO! Definitely DO NOT try to bend the needle.

Fuel gauges (of all types) are notoriously inaccurate, so you need to decide which end of the scale you really care about.
Personally, I'd rather know when I'm going to run out, so that's the reading I concentrate on.

First, drain the tank (fortunately, FCs have a tank drain, so this is easy).
Add about 1/2 gallon back in, just to have a bit or wiggle room.
Now, you need to pry the needle off it's shaft. There are special tools for this but you can sometimes use two flathead screwdrivers to pry upwards and remove the needle.

Once removed, make sure you have the ignition ON and gently press the needle back down on the shaft (which is very thin, so be careful). With luck, you can position the needle right on the EMPTY mark but this may take a few tries. Once you're happy, put everything back together and go fill the tank. It takes a few minutes for the gauge to reach its final reading, so be patient.
Whatever it reads is what it's going to be but you should be fairly confident that at the low end of the scale, you're probably pretty close.
If you're really into it, drain the gas (or just run the car till it dies) and see where the needle now falls.
Just remember, these are not precision gauges and will never be totally accurate or consistent.

 

I bent the needle on mine when i was replacing the fuel pump and worked pretty well. Maybe I was lucky. Mine was over 1/4 tank off before that Kinda like Aceangal and read at less then 3/4 tank when full. Now it is pretty good. I mainly use the trip meter every time I fill up so I can count on that as well.

 

hope you have a spare gauge if you try pulling the needle off...unlike other oem gauges these are very hard to get off without breaking...found out the hard way.

 

i would be happy with it reading on the conservative side, but not saying I have 1/4 tank and running out
im not going to pull the needle off, ill probably break it lol

it was working fine until I redid the fuel lines and fittings, it must have gotten bumped around and lost its setting . not an issue when I keep the car locally but if I want to go on a trip it sucks factoring it in at 10-12mpg

 

You know you can test your gauge to see if it's off instead of bending the needle like an idiot. People make things so much harder than they have to be. It's most likely the sensor failing. You can even test that too.

 

maybe instead of saying we are all idiots you can share the testing procedure?
maybe you missed the part where I said you can take a reading of the resistance but from there how do you correct it and how does that translate into a real life driving situation.

 

My FB says a quarter tank when it's empty. My Fc shows a quarter tank when I have a half tank. My Fd shows a quarter tank when there is a quarter tank. Who cares. I know when to get gas.

 

That's not quite what I said. Would you say that bending the needle is good advice? If I were to see a guy bending his classic rx-7 gauge cluster to compensate for an electrical/sensor issue, I would probably think to myself, "What a ******' idiot.".
You've posted 8600 posts. I would imagine you would've read the FSM front to back by now. I believe the information you are looking for is in the Body Electrical section. You're gonna need resistors to test your gauge to mimic your fuel level sensor. You'll also want to ensure that you have no resistance in your wire as that will affect the reading. Checking the sensor with a digital meter won't work. You'll need an analogue meter to properly test the sensor.

The sending unit is less than 100 US at Mazda. If it is your sensor it's not that bad of a punch in the wallet. Everything costs a hundred bucks on this car. And if you're fuel light doesn't work, bonus 'cuz that is part of the unit too.

 

All of that pomp and posturing for nothing..

You know, some of what you said isn't half bad.. but the real kicker is that you seem to have little in the ways of reading comprehension.
Go back to measuring your dick. Maybe you'll get that extra couple inches you so desperately want.

Oh, and everything on these cars is not a hundred bucks...if that were true, many of these cars would be in far better condition.

 

i bent the float arm on one of my FC's. its a bit of an odd deal, you need to have the sending unit out of the car, and the car on. you basically move the float all the way up, and wait for the gauge, and then all the way down, and wait again, and then about half way, and wait. its a bit fussy, but its simple.

with mine, before it would be on E and have 5 gallons left in the tank (5 of 16 gallons), and after when it was on E it was EMPTY, so you do want to leave some fudge room. factory spec is about 2 gallons on E, not that anyone has time to measure that (unless you're in the SCCA, then its probably in the rules), but it gives an idea what you're looking for

 

I could think of a couple reasons why these cars are in the condition they're in lol. My "reading comprehension" is fine. I didn't see any mention of the Factory Service Manual(church choir music). Aside from that there is priceless info archived on this very subject.
I'm just trying to be a voice of reason. If you read again and try not to get emotional about it you'll see that it was quite justified. In any case I didn't mean to get your panties all bunched up. Sorry about that.

 

I go commando, but thanks.
I'm sorry too...sorry you acted like a child and got your pee-pee smacked.

 

I actually have a hard copy of the FSM, and while I admit that even with the amount of posts I have made on this board I have not read it cover to cover and memorized it. I didnt see it.
Maybe its buried in the specifications section or im just blind, but I did not find the specs on the resistance for the sender during the 10 minutes I read through it while in my library

either way if your intention is to be helpful perhaps you could point out where specifically in the manual it is otherwise you offer no help. The forum is not exactly over flowing with active topics but its very easy for you to just click out of it if you cant offer actual helpful advice

 

its in the body section i think, 15? there is a bit about the gauges

 

my gauges have always been great, I know people complain about them but besides my tach being a little off the rest of them are very accurate
the cluster has never been removed, the issue I believe is with the sender itself