Over the holiday weekend we took the truck on its first, long trip. During fuel stops I noticed one big difference between the new diesel and my old Burban which was a gasser. When I opened the fuel cap, I heard a whoosh of air as it was entering the fuel tank; very similar to the sound that you would hear when you first puncture a fresh can of coffee. This happened with the old gasser, but only on extremely hot days. Is this normal?


Since I'm new to this forum, I'm still not feeling completely comfortable about the kinds of issues that I should post here. I posted the tank vacuum question on another diesel forum. Other than raising more questions than answers, I'm no further ahead. A couple of people suggested I "modify" the tank cap. Being from NJ, an almost socialist state, the suits would take your kids away if they caught you messing around with emission equipment. So I have another question and feel free to tell me where/if I went wrong. Should I expect an answer to my question? What happens if people stop posting replies and you still don't have an answer? Do you go to the administrator? (Now I'm beginning to feel like I'm back in grade school.)

sounds as though i have a faulty fuel cap.

Spin you hit the forums at a bad time of the year, holidays in the air, cold weather nobody working on their trucks, and for me this is prime hunting season so I don't stay on the forums as much as other times, or I'll want a change of pace from Diesels shift gears and visit other sites, lately Iv'e been visiting military sites I'm a Navy veteran, these forums sort of go in spurts, persistance sometimes is what it takes.


As for your cap issue varied opinion on this one, I drilled mine when I 1st joined over at TDP as that was current thinking of some, I've since plugged the hole, sometimes I have pressure, sometimes I have vac, just depends on ambient conditions of the day. My opinion others will have theirs, your cap is okay leave as GM designed it.


In my neck of the woods hi humidity open cap has potential of admitting water via condensation hot tank from fuel return cool day low dewpoint just might do more harm than good.


This is one of those topics that opinions are so varied you'll have to form your own decision on what has been presented, also on topics like this one that had a lot of traffic in the past, the different "camps" of an idea may not want to participate in another rehash, I don't know this topic to be in that situation, but talk topic of fuel filters and whole mess o worms on that one, sorry I can't offer more.Edited by: Turbine Doc

Spin


did you check to see if your fuelcap was operating properly? By placing the threaded end over you mouth you should be able to suck air in "as in into the tank" and not be able to blow through the cap as in expell air from the tank. commonly referred to as Kennedy's lip lock test. if your cap does not operate as noted it should be replaced if it does you are developing pressure in the tank not vacuum. pressure is good as it assists you lift pump.


john

thanks...this is exactly the kind of info i was looking for.