1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Gas tank level question (am I out of gas lol)

Old Aug 5, 2009 | 08:58 AM
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Gas tank level question (am I out of gas lol)

So I added alil more than a gallon, I tried to drive as little throttle I could going 60-70mph 40miles.

So thats probably 2 gal at the most.

The gas level went from inbetween the /// (The low gas light area) stuff and the next line roughly (84-85 dash) to the /// stuff, or right above like a few hairs.

Do I have enough to do this drive back without running out? I was going to look at the fsm but I'm sure somebody else might know, I knew my fc gauge good but I've been to scared of taking the FB low, my fc ran out one time, very bad night lol.

I put all the change I had in the tank though to get that 1.5gal

Oh, the gas light isnt on yet, idk it seems the sensor is kinda in accurate if I let the car sit (running) it goes up alil higher slowly I noticed so when it's at the low area do you got like 30 miles or so? I might beable to find a few more quarters haha
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Old Aug 5, 2009 | 09:15 AM
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From the right side of the "empty" line to the left side of it I can usually go fairly far. In fact I think I've had it past the empty line once before, although not for very long. Most cars can go a surprisingly far distance on empty. Probably a smart move by the OEMs making the gauge show empty before the tank is actually close to empty. Gives you a little more time to get some gas. If I were you though I'd find someone to borrow a few bucks from. Better to owe a couple bucks to a buddy then need a tow or have to walk 20 miles to get help.
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Old Aug 5, 2009 | 09:18 AM
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Well the drive is just freeway maybe if I limp it and go 50 instead of 60-70 (the speed limit was 50 on one part, and 65 on the other part)

It's just about 40 miles, I just went to meet some people I never have, don't really wanna beg for cash

It's alil above where the empty part starts... like 1/4th cm. It actually only moved maybe alil more than 1/4th a cm, if it moved another 1/4th cm it'd be in between the low gas marks....

I've taken it till alil above the very last of the low gas mark where it goes like ////.

Do you have a S3?
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Old Aug 5, 2009 | 01:12 PM
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Well I got home, no edit button so sorry for double post.

Nice people shot me 10 on gas since the way to their house (hwy) has tons of up and downs.

I'm still curious how low a S3 gauge will go so please do tell ppl, I think I'm going to run it down this time till the bone by a gas station with some seafoam mmm
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Old Aug 5, 2009 | 01:52 PM
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this may help. if you drop the tank and pull the sender, here are the resistance values then testing the sender:

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Old Aug 5, 2009 | 09:39 PM
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I was looking at that in the fsm.

I was trying to figure some way to do math and figure it out but the tank isnt the same size all through is it?

On my fc Full - > med would go "fast" then it'd stay at med forever, serious. As if it was a lot bigger at med.

Then low, oh low was LOW. Sometimes it'd run out of gas before the level was even all the way down haha
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Old Aug 5, 2009 | 10:48 PM
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yeah, you have to pull the sender, and move the arm on the sender and measure the resistance. easy do on the bench. often times, where the sender grounds to the upper portion, it corrodes and the resistance values are way off due to the lack of a proper ground.

Last edited by mazdaverx713b; Aug 5, 2009 at 11:01 PM.
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Old Aug 5, 2009 | 10:51 PM
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Ummmm.. that picture posted up there is for Oil pressure...?

What manual can I find that in..? All I have for the 1st gens is a Haynes.

My gas gauge is acting funny. Works, and then drops to as if I'm empty, works, and then gets stuck at 3/4...??? Been doing it for over a year now.
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Old Aug 5, 2009 | 10:57 PM
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let me correct that. guess i posted the wrong pic....
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Old Aug 5, 2009 | 11:00 PM
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this is the correct one. clicked on the worng pic link:



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Old Aug 6, 2009 | 10:11 PM
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Nice thanks...
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Old Aug 6, 2009 | 10:26 PM
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i dont know what i was thinking ..must have lost my damn mind...
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Old Aug 7, 2009 | 12:08 PM
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From: https://www2.mazda.com/en/100th/
Originally Posted by cmanns
I was looking at that in the fsm.

I was trying to figure some way to do math and figure it out but the tank isnt the same size all through is it?

On my fc Full - > med would go "fast" then it'd stay at med forever, serious. As if it was a lot bigger at med.

Then low, oh low was LOW. Sometimes it'd run out of gas before the level was even all the way down haha
i tested my FC when i had the sender out, the gauge is right.... halfway on the sender = halfway on the gauge etc etc
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Old Aug 8, 2009 | 07:45 AM
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Low fuel level light comes on when there is approximately 2.1 gallons of fuel left. Guess where I found that tidbit?
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Old Aug 8, 2009 | 11:03 AM
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From: https://www2.mazda.com/en/100th/
Originally Posted by trochoid
Low fuel level light comes on when there is approximately 2.1 gallons of fuel left. Guess where I found that tidbit?
2.2 gallons away from a gas station?

its in the owners manual, in high school you were ok until the gas light stayed on solid, then you needed fuel. actually i still do that, but the current FC has 3 gallons when the light is on
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Old Aug 8, 2009 | 11:08 AM
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Yep, the owner's manual, but that shouldn't have been hard for someone who probably has every manual, microfische and written word published regarding 7s, lol.
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Old Aug 8, 2009 | 05:55 PM
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ooo it comes on at 8 liters... 2.1 sounded like a weird number to me but if you convert it from gallons to liters, it's right at 8
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Old Aug 10, 2009 | 08:09 PM
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Yep and 1.8 Imperial gallons. The owner's manual is quite handy somedays.
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Old Aug 10, 2009 | 08:14 PM
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From: https://www2.mazda.com/en/100th/
Originally Posted by trochoid
Yep, the owner's manual, but that shouldn't have been hard for someone who probably has every manual, microfische and written word published regarding 7s, lol.
=) i try!
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Old Aug 10, 2009 | 11:55 PM
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You should never go under the last 1/4, its possible for you to pick up sediments and clog up your fuel system. I seldomly go under the last 1/4.
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Old Aug 11, 2009 | 12:53 AM
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Well I got a new fuel tank and lines so it's pretty clean, the fuel filter with god knows how many miles I cut open and it looked as new as the new one, which was clear.
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Old Aug 11, 2009 | 03:12 AM
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Originally Posted by R-cien
You should never go under the last 1/4, its possible for you to pick up sediments and clog up your fuel system. I seldomly go under the last 1/4.
That's a nice thought, but easily rectified by draining and sealing the fuel tank. Which most that I've seen are in need of. As old as our cars are getting, it's becoming a standard preventative maintinance proceedure. It costs me less than 100 bucks for materials and labor to have a tank boiled, then bring it home and seal it, along with addressing any rust spots and refurbishing the exterior, replaciing rotting fuel lines, etc..
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Old Aug 11, 2009 | 05:17 AM
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Oh and yeah 2gal would be right I'd say, now I don't feel bad driving it with the gas light on lol, I still havent drove it till it sputtered like my fc (which would still go like 5 miles) but I feel safer taking it down to the last lines
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Old Aug 11, 2009 | 11:19 AM
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From: https://www2.mazda.com/en/100th/
Originally Posted by cmanns
Oh and yeah 2gal would be right I'd say, now I don't feel bad driving it with the gas light on lol, I still havent drove it till it sputtered like my fc (which would still go like 5 miles) but I feel safer taking it down to the last lines
it has a carb, so it wont sputter, you're just out
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