Gas leaking from my vent solenoid aka Vapor Canister Purge Valve - Blazer Forum

cmaddox421 · #1 06-29-2010, 11:44 PM

Just wondering if anyone knows of some common causes of gas leaking out of the Vapor Canister Purge Valve only when the vehicle is running and if simply relplacing it is all that is necessary. This is on my 1999 Trailblazer 4.3 V6 4x4. Recently had the fuel pump replace (2-3 months ago).

Thanks for any help!!!

RonJon · #2 06-30-2010, 06:04 PM

Whatever the cause is for gas to come out of the vent solenoid I don't think it's "common". Only suggestion I can think of is replace the charcoal canister. (probably cheaper to get one from a boneyard). That canister has 3 lines: vapors from the tank, air from the vent solenoid, and separated fuel that goes to the purge solenoid on the engine. Whatever is in the canister that separates things and lets them flow to the proper places (check valves I'm thinking) has gone badly wrong I'd say. I'm amazed there's no check engine light and I can't think of any way a fuel pump replacement could cause this issue.

cmaddox421 · #3 06-30-2010, 06:26 PM

RonJon,

Thanks for taking time to respond to my post. The check engine light has come on, but it kept going off. We just today ran a diagnostic check at AutoZone and it said that the fuel tank pressure sensor is bad. Could this be the cause of the problem?

RonJon · #4 06-30-2010, 07:09 PM

The thing I'm trying to figure out is where pressure is coming from to lift fuel to the level of that vent solenoid. Only thing I can figure is when the purge solenoid opens on the motor the liquid fuel in the purge line is siphoning back through the canister. (engine is above that level, rest of the system is below it). Personally I'd say the canister is flawed and the trouble code is due to the EVAP system not working as expected by the Powertrain Control Module. The fuel system is always generating negative pressure at the tank because it's always pumping out more fuel than what returns (while the engine is running). It's possible the pressure sensor has a flaw (or your mechanic didn't plug it in well while replacing the pump) but that wouldn't cause the fuel coming out of the vent solenoid. I still say start with the canister.

surfing007 · #5 06-30-2010, 07:15 PM

How did you notice the leak? I have had this problem also, but have not been able to find the exact location that the gas is leaking from.

cmaddox421 · #6 06-30-2010, 07:49 PM

Surfing007: Well, I ran into the store and left my wife and kids in the blazer. We kept it running because it was gonna be a quick trip in and she wanted to run the A/C. When I came out, I saw the puddle underneath the rear of the vehicle and it was gas. I could see that it was dripping onto then off of the spare tire, so I took the spare off. I put my finger underneath the vent solenoid, behind the bracket that holds it and could feel it coming out the bottom of the solenoid.

RonJon: Thanks for the info!! It is likely that I will start with a boneyard canister... new is like $150+. Just in case though, is there anything else that might cause the excessive build up of pressure? Are you sure that improper installation of the fuel pump can't be to blame? We've been smelling the gas since the repair. You've been a great help, thank you!