Never had a problem until about 3 days ago. I was nearly empty, filled it up, and the gas gauge only read about 3/4 of the way full. I started driving it and it eventually went all the way up after about 15 minutes. It doesn't have a problem going down, but when I go to put gas in it, it takes awhile for the gas gauge to show it. Any ideas?

 

I had this happen to me after I put my standalone ems in even thought they dont have anything to do with each other.

But I wouldn't be to worried it happens to me once in the blue moon.

 

I ended up running a can of sea foam through the gas tank and that seemed to fix the problem for the time being. We'll seee

 

I see this issue on many newer cars and my s2000 as well. It happens to me 100% of the time if I fill up with the car/key in the OFF position. If I fill up with the car either RUNNING or the key atleast in the ON position, the gauge will register FULL once filled. Its a weird issue, but you are not alone. I seen it on many s2000s, STIs, evo's, BMWs, etc and it usually happens when the car is OFF and the key is totally in the OFF position or out of the car all together.