i have a s5 guage, and the neddle will be at say 3/4 and ill come out the next day and its at 2/3 ect. it does it no matter where the needle is it'll drop an 8th tank or so and not go back up.
im thinking my tank or something is leaking. but then why do i still get suction when i remove the cap? theres no visibal leaks, and no ones driving it either.

im thinking in this order
1) gasket for the fuel pump is bad, where could i get one cheap?
2) bad charcoal canister maybe?
3) an actual leak and its evaporating off the ground too fast to notice

 

your gas cap could be leaky, thats an easy 7 dollar fix.

id try that before getting gaskets and such, thats more work. if all else fails you have an extra gas cap, your bound to leave one on your car and drive off without it on one of these days heh.

 

yeah, dn that a few times...
but it fits snug and i get thet crazy suction when i remove it

 

With my 91 I notice that I have to turn off the car, then the gas gauge will read more accurately. When I go for long drives, the gauge barely goes lower than when I started, but the next time that I drive it (next day or so) the gauge will be a lot lower.

 

I get that alot too actually, Its kind of upsetting when your like wow i went along ways and the gauge barely moved, park the car come back later start driving and a quarter tank is gone

 

+2, I get the same thing, I never trust the guage after it's below a quarter tank

 

Is the fuel actually missing from the tank or it is just the gauge?

The reading in the fuel gauge can be effected by temperature since it is a bimetallic gauge. Or it could be sticking, as can the fuel sender.

 

I dont trust my fuel gauge these days, i just know I get 14-15 mpg and fill up accordinly. I use the little trip meter under the miles and fill up usall around 160ish miles which is usally 10-11 gallons of gas.

 

Same here, except I get about 275 miles and put ~ 14 gallons in. I don't really look at the gauge.

 

That's pretty decent milage.

 

electrical problem

come on, rx-7's have notoriously shitty gas gauges. i think hailers or Ted just made a thread recently about replacing your sending unit

 

Not bad for TII huh? It's about what I would have expected. A TII in good condition/tune with no performance mods should do that easily.