Newbe fuel leak issue

[GonzoTB]

Hey everyone,this looks to be a living breathing new GM fan forum.First off I am a GM loyalist,dont know why so many people will flip to any manufacture that comes along.I grew up Mopar but went GM after my second car at age 17.

02 TB leaks fuel after fill up from the evap solonoid vent thats at the back of the fuel tank.It leaves a small pool on garage floor the next morn.I gather that no fuel should be getting there,its only to vent fumes? whats causing fuel to get pushed out the vent???No codes ,runs fine 130k mi great overall condition.Appreciate help on this before throw parts at it.Im sure this issue has been corrected a million times in the past.

This leak is not coming from the fill pipe and not from the top of the fuel pump modual.I took the tank down far enough to verify.I hope there are some wordclass GM techs that hang here,although anyone here thats been through this issue doesnt need to be one to help.Enough rambling.congrads on new site!:wootwoot:

 

[mika]

Just a stab in the dark, did you chech to see if there is any feul lines that run over the evap lines that might be leaking?

 

[GonzoTB]

Hey Mika thanks for responding to my post.I was able to get a good look at everything because i pulled the skid plate and lowered the tank about 8" or so.I have a twin post so it makes it easy to see everything,no lines leaking or seeping.Im convincend the fuel is being pushed out the evap solonoid vent.Anyone know the function of the solonoid? I gather it opends and closes to control fumes only???

 

[The_Roadie]

The system is indeed supposed to deal with fumes only. The vent solenoid valve I assume you're looking at is normally open while running, to allow outside air to enter INTO the carbon pellet-filled canister. When the EVAP purge solenoid on the engine opens under PCM control, engine vacuum sucks fuel vapors from the canister into the engine. If the canister saturates with liquid fuel, that's a problem, and might be due to a purge valve fault. But as I understand it, the vapor flow should be from the vent solenoid TO the canister TO the purge solenoid TO the intake manifold. Liquid fuel shouldn't ever be present at the vent solenoid.

The PCM is always running diagnostics to check for large and small leaks of vapor since it's such an emissions issue of they escape unburned into the atmosphere. Solenoid faults and leaky hoses should ALWAYS result in a Service Engine Soon light, and a code you can read. If you're not getting codes, then I'd assume there aren't any leaks in a monitored area.

Are you sure it's not the fill limiter vent valve that's leaking fuel instead of vapors? Does your leak only happen after a fill-up?

A mechanic with a high-end scan tool or a GM Tech II can command the solenoids to close and open, and check pressure on the system and possibly cause the leak to happen.

 

[GonzoTB]

Everything on top the tank was bone dry,it is damp on side of the tank below the solonoid,its not damp on the other side of the solonoid.As far as when it leaks,i assume its when she fills it up and drives home and over night it shows on the garage floor.Im not for sure this is when it drops fuel.I will clean the spot and take note if its only when its just filled.


link to good diagrams
GMT360 Fuel Tank Replacement (SWB)

 

[GonzoTB]

dry as a bone on top the tank,damp on side of tank below the solonoid dry on other side of solonoid.Not 100% sure if it only leaks when filled up and parked in garage over night. i will have to watch for it when it does drop gas.

found this link with great diagrams
GMT360 Fuel Tank Replacement (SWB)

 

[GonzoTB]

The system is indeed supposed to deal with fumes only. The vent solenoid valve I assume you're looking at is normally open while running, to allow outside air to enter INTO the carbon pellet-filled canister. When the EVAP purge solenoid on the engine opens under PCM control, engine vacuum sucks fuel vapors from the canister into the engine. If the canister saturates with liquid fuel, that's a problem, and might be due to a purge valve fault. But as I understand it, the vapor flow should be from the vent solenoid TO the canister TO the purge solenoid TO the intake manifold. Liquid fuel shouldn't ever be present at the vent solenoid.

The PCM is always running diagnostics to check for large and small leaks of vapor since it's such an emissions issue of they escape unburned into the atmosphere. Solenoid faults and leaky hoses should ALWAYS result in a Service Engine Soon light, and a code you can read. If you're not getting codes, then I'd assume there aren't any leaks in a monitored area.

Are you sure it's not the fill limiter vent valve that's leaking fuel instead of vapors? Does your leak only happen after a fill-up?

A mechanic with a high-end scan tool or a GM Tech II can command the solenoids to close and open, and check pressure on the system and possibly cause the leak to happen.

IM back,all of this time I have let this problem go unresolved,just bought the wife a new 013 malibu.Its time to sell the TB and want to fix this before I sell.It still looks like fuel comes from solinoid vent,it does it sometimes the first night after a fill up.At one time it would leave some on the floor.for quite some time it hasnt leaked enough to hit the floor but make the side of tank wet.

Mika you mentioned a fill limit valve,if that was the issue would that allow fuel to be pushed out the solinoid vent? Still never any codes on the TB

Thank you all for this fantastic forum.GonzoTB

 

[BRomanJr]

IM back,all of this time I have let this problem go unresolved,just bought the wife a new 013 malibu.Its time to sell the TB and want to fix this before I sell.It still looks like fuel comes from solinoid vent,it does it sometimes the first night after a fill up.At one time it would leave some on the floor.for quite some time it hasnt leaked enough to hit the floor but make the side of tank wet.

Mika you mentioned a fill limit valve,if that was the issue would that allow fuel to be pushed out the solinoid vent? Still never any codes on the TB

Thank you all for this fantastic forum.GonzoTB

Most vehicles have a rollover valve to stop fuel from leaking out when "rolled over" this should also prevent raw fuel from getting into the vapor/vent system.

Also, Please be sure you and/or you wife are not "topping off" the tank when getting fuel, it can saturate the charcoal media and cause raw fuel spills. sometimes a hard start or stumbling when the purge cycle runs.