2007 Ion fuel filling problem

[Richard B]

2007 Ion keeps shutting the nozzle off at the gas pump. Although, turning the gas nozzle upside down seems to help. The three nipples on the evap canister all accept and discharge air blown into the canister. The vent valve on the canister is open. And there are no charcoal pellets outside of the canister. What is the purpose of the third (smallest) tube that runs parellel with the fuel fill tube and evap vent hose. Could the problem be a stuck rollover valve or fuel tank over-fill valve? And if so, where are they located and how do you test and repair or replace them? Any help will be greatly appreciated.

[fdryer]

Presuming zero error codes, do other gas station nozzles shut off prematurely? Determine whether one or many fuel nozzles shut off prematurely to conclude a problem with your car or one pump nozzle is more sensitive to your car.

All gas station pumps use a low vapor pressure feedback sensor to automatically shut fuel dispensing to prevent overfilling/spilling fuel. Our vehicles use a fuel vent tube to prevent fuel vapor pressure buildup triggering the pump shutoff system.

[Richard B]

Thanks fdryer for addressing this issue. I should have pointed out that the nozzles at many gas stations have repeatedly kicked-off the same way. Unfortunately, I don't understand what the sub-components on the gas tank do. In addition to the large hole for the fuel pump assembly, there are two small holes with white plastic inserts to either side the the pump that are connected by a hose. One has a second hose, which is the tank vent hose leading to the input nipple on the charcoal canister. I just wish I knew what was under those white plastic ports. Is one an overfill valve designed to shut when the fuel level in the tank reaches a predetermined level? If so, could a float be stuck that is causing pressure to build up in the tank? And if that's the case, what is the purpose of the other one. Is there a roll-over valve? What is the function of the smallest hose in the filler neck assembly? Sorry, lots of questions. I have spent dozens of hours researching, which has provided me with a lot of information; just not the answers to the problem I'm having.

[fdryer]

With several gas stations shutting off prematurely, this points to your fuel vent line. Info I've learned from my service manuals (L300) describes the fuel vent valve is open to the atmosphere with engine off when filling the gas tank. The vent valve closes with the engine running to seal the fuel system. As vapor pressure rises, the charcoal canister is opened and vacuum pulls vapors in. Emissions controls opens another valve to feed captured fuel vapors to the intake manifold. The fuel vent valve in open position allows fuel vapors from filling the tank to freely leave but if its stuck closed won't allow vapors to vent and trigger the gas station pump to shut off. 12v operates the fuel vent valve; unpowered/open venting for tank filling, powered closed to seal the fuel tank as the evaporative system captures vapors into the charcoal canister for feeding vapors into the intake manifold while driving.

I can't answer all questions but service manuals can. Either a subscription, one time fee for a few days, library access to alldata, etc.

I do know two fuel pipes for some Saturns are for main fuel feed (the larger pipe) to the fuel tank with an anti siphon valve to prevent siphoning fuel and a smaller vent line to the fuel tank and fuel vent valve near the fuel fill pipe. This description is from my L300 as the smaller vent pipe corroded until it opened with an intermittent error code becoming permanent when the vent pipe broke open. Replacing the assembly corrected the error code.

I don't know what the third line is for.

[Richard B]

Thanks, fdryer, good advise. I think I'll go back to ALLDATAdiy. They were pretty good when I owned the SL2.

[dcjredline]

Id guess yer vent valve or the hoses are bad. The vent allows pressure to escape as you fill. The nozzle shuts off because pressure is building up in your tank and the nozzle sensor thinks you are getting close to full