Gas Needle Question...

[qx4dude]

Hello,

Last night i filled my truck up with gas (always premium) and my needle is not quite showing full. It is sitting between the full line and the 7/8ths line. I double checked the tank was completly full by topping it up again this morning. Anyone else ever had this? Im pretty sure everytime i have fill the need has gone right to the top of the full marker. I just replaced my fuel filter so i hope this has nothing to do with that. Its not a huge issue i guess just a little weird.

Any input is great. Thanks

[KyooX4]

I don't know. Mine has always been weird too. When I fill up the tank the needle on the gas gauge is over the full tank line, then when it hits 1/8th of a tank, the gas light comes on.

[Densetsu]

Could be your EVAP system.

The nozzle on a gas pump hose has a small hole at the very tip. When the fuel flows into your tank, air is drawn into this vacuum hole with little resistance. However, as soon as the fuel in the tank gets high enough to reach this tip, fuel is drawn into the small hole. The heavy fuel doesn't flow as easily as air would, so it trips a switch and turns off the nozzle.

(That's the gist of it... a more detailed explanation is here: http://www.wonderquest.com/sle...zzles)

However, if your gas tank isn't venting properly, there will be a pressure differential as the tank fills up. Eventually, this will trip the nozzle and turn it off, since with the additional air pressure it thinks it's begun to suck fuel up the little vacuum hole.

If you can, check the codes. I can see some EVAP codes not being critical enough to turn on the check engine light, but they'll still be stored.

[Pwnin O'Brien]

I don't know. Mine has always been weird too. When I fill up the tank the needle on the gas gauge is over the full tank line, then when it hits 1/8th of a tank, the gas light comes on.

This is normal. When you fill up it should go above the full line; likewise, the gas light should turn on when about 1/8th of a tank remains.

[qx4dude]

Could be your EVAP system.

The nozzle on a gas pump hose has a small hole at the very tip. When the fuel flows into your tank, air is drawn into this vacuum hole with little resistance. However, as soon as the fuel in the tank gets high enough to reach this tip, fuel is drawn into the small hole. The heavy fuel doesn't flow as easily as air would, so it trips a switch and turns off the nozzle.

(That's the gist of it... a more detailed explanation is here: http://www.wonderquest.com/sle...zzles)

However, if your gas tank isn't venting properly, there will be a pressure differential as the tank fills up. Eventually, this will trip the nozzle and turn it off, since with the additional air pressure it thinks it's begun to suck fuel up the little vacuum hole.

If you can, check the codes. I can see some EVAP codes not being critical enough to turn on the check engine light, but they'll still be stored.

So if this were the case, your saying my tank would not actully be full?

I thought maybe this was the case so i returned to the gas station to top it up. I basically filled it untill a little I had a little splash back of gas. So this makes me think my tank is indeed full, but the gauge is incorrect?

Maybe it will work its self out when i fill up next?

[Densetsu]

So if this were the case, your saying my tank would not actully be full?

I thought maybe this was the case so i returned to the gas station to top it up. I basically filled it untill a little I had a little splash back of gas. So this makes me think my tank is indeed full, but the gauge is incorrect?

Maybe it will work its self out when i fill up next?

That *is* odd. Usually when a gauge is messed up, it's completely dead. Not just off by 10% or whatever.

I wouldn't worry too much about it, but keep it in mind when you're planning long trips. Whenever I had problems with filling up, it was because it wouldn't fill up all the way -- and that went away within a few weeks.

[qx4dude]

Ok thanks. I just filled up last night so lets hope it just works itself out. I just thought it was odd because i know the needle always goes over the full mark after filling and this time it was sitting under and it was indeed very full!

Thanks again.

[Pwnin O'Brien]

Ok thanks. I just filled up last night so lets hope it just works itself out. I just thought it was odd because i know the needle always goes over the full mark after filling and this time it was sitting under and it was indeed very full!

Thanks again.

If the needle works normally and this time it didn't I would probably just guess your fuel sender arm probably just got stuck and couldn't go any higher, making you think there is less gas in the tank. Maybe a few good bumps will un-stick the arm.

[qx4dude]

If the needle works normally and this time it didn't I would probably just guess your fuel sender arm probably just got stuck and couldn't go any higher, making you think there is less gas in the tank. Maybe a few good bumps will un-stick the arm.

Thanks i think your right. WHen i started my truck last night after work, the needle seemed to be sitting in a better place. Lets hope its normal when i fill up next time. Thanks again