Help regarding Fuel venting system
Thread Starter
|
Senior User
Joined: Mar 2002
Posts: 132
Likes: 0
From: Castle Rock, Co
Help regarding Fuel venting system
Just got back from the Stealership (read Meron vs Mercon V in Superduty forum) and asked that they check the fuel tank vapor carbon canister system for the THRID time under warranty. Inside and outside of my truck, on warm days, you can occasionally smell gasoline odors. Thanks to this forum I learned that there is a carbon canister above the front left wheel well. Nobody else that I know of with a 99 or newer gas powered truck F250 has this problem. I thought that someone posted that this fuel vent system is under about 2 psi and asked the stealership to check the PRV or whatever else could cause a release of vapors. Well, they said the system is freely vented and there is nothing they can do. Because of their help with my tranny (other post mentioned) I may ask them to replace the carbon canister. I do not overfill my tank and this problem has occured since the first summer I owned my truck. Anybody else have this problem or does anyone have any advice?. My Haynes manual does not even mention the canister but shows it in a photo. BTW, searched this forum first for the Mercon Vs. Mercon V info. Very helpful as usual. Bye, have to call for a tow truck.
Posting Guru
Joined: Apr 2003
Posts: 1,089
Likes: 1
From: Michigan
The fuel vapor canister (charcol canister) is a buffer that stores fuel vapors that build up in the system during normal operation. At times the PCM will command the VMV (vapor managment valve) to open and PURGE vapors from the canister back into the intake. There is another valve on the canister inself called the CVS (canister vent solonoid), it is normally open, but NOT to vent fuel vapors to atmosphere, there is a check valve to prevent that. It needs to be open so when the VMV is pruging vapors back into the intake using vacumm, the tank isn't sucked in and colapsed. It only is commanded closed when the PCM preforms an OBDII PURGE monitor test which looks for fuel vapor leaks. I suspect that the check valve is bad on or near the CVS, and what you are smelling is vapors from the canister that are escaping. NEVER, under normal operation will raw fuel vapors be vented to atmosphere.
Thread Starter
|
Senior User
Joined: Mar 2002
Posts: 132
Likes: 0
From: Castle Rock, Co
Follow up - Just before my truck went out of warrenty I thought I'd bring it in for the fourth time to solve the gasoline odor problem. Thanks to the informative post above I had confidence something was wrong (actually made the service manager read it). This time they found it, the vapor vent line leading to the carbon canister had a cracked (pushed in) fitting at the canister. Replaced the fitting/canister and problem solved. The senior mechanic who worked on it said in all fairness to others that attempted to fix it that it was not easy to find and that he got lucky. Boring post, yeah, but I'm glad it's fixed. Thanks guys.
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
Another BS story from a dealership tech.
My '01 (granted, that might be different than your '99, but I seriously doubt it) has the Evaporative system pressure test "bung" right there under the hood.
That's so they can hook up a leak tester to pressurize the system (w/smoke machine?), and check for leaks. If they had done that, they would have found the problem, or at least that you were not crazy and you DO have a leak
Amazing...
My '01 (granted, that might be different than your '99, but I seriously doubt it) has the Evaporative system pressure test "bung" right there under the hood.
That's so they can hook up a leak tester to pressurize the system (w/smoke machine?), and check for leaks. If they had done that, they would have found the problem, or at least that you were not crazy and you DO have a leak
Amazing...
Thread Starter
|
Senior User
Joined: Mar 2002
Posts: 132
Likes: 0
From: Castle Rock, Co
krewat, I are right on the money as usual. This service manager, at least the third one in 3 years, was very helpful and mentioned he would have a smoke test performed. Evidently common knowledge to some people but then how come they never did it on the first three tries. It is a PITA to take time off, drive down and wait/kill time when it seems they don't really try or care to solve the problem. A good mechanic is hard to find and worth paying for.
Since this problem should have been diagnosed sooner and the fact that they put mercon V in my tranny I have very little faith in that or any dealership.
Since this problem should have been diagnosed sooner and the fact that they put mercon V in my tranny I have very little faith in that or any dealership.
FTE Leadership Emeritus
Joined: Jul 2002
Posts: 42,561
Likes: 423
From: Long Island USA
Originally Posted by Fords For Ever
krewat, I are right on the money as usual. This service manager, at least the third one in 3 years, was very helpful and mentioned he would have a smoke test performed. Evidently common knowledge to some people but then how come they never did it on the first three tries. It is a PITA to take time off, drive down and wait/kill time when it seems they don't really try or care to solve the problem. A good mechanic is hard to find and worth paying for.
Makes me wonder sometimes...
Good luck with it in the future!
Thread
Thread Starter
Forum
Replies
Last Post
alchemist1
1973 - 1979 F-100 & Larger F-Series Trucks
17
Mar 18, 2020 07:24 AM
TheRedBeast01
Modular V10 (6.8l)
12
Jun 30, 2014 11:09 AM
athenshome
1997 - 2006 Expedition & Navigator
3
Sep 25, 2013 11:25 PM
