Topic: Should the fuel tank be pressurized?

[jfrabat]

Yesterday I went to fill up my Jeep, and, like always, there was some pressure difference between the tank and the ambient pressure (you can always hear some air hissing), but this time, I took the cap off fast enough that the pressure actually pushed the cap out; I think I remember Jeffy saying at some point that is not supposed to happen, but it did, and I want to verify this is in fact so, and if it is NOT supposed to happen, I would like to hear your opinions as to what could cause this to happen...

[sharpxmen]

i remember reading about it in the FSM but i can't recall all the details exactly, it should hold some pressure but what you describe is probably more than usual (never happened to me, so that's mainly what i go by).

[Danny in Galveston]

The rollover valves on the top of the tank will allow about 4 pounds of pressure before venting it to the evaporative fuel emissions system, but what you describe sounds like excessive pressure.  Could be a blocked vent line or both rollover valves are stuck closed.

[jfrabat]

The rollover valves on the top of the tank will allow about 4 pounds of pressure before venting it to the evaporative fuel emissions system, but what you describe sounds like excessive pressure.  Could be a blocked vent line or both rollover valves are stuck closed.

Well, I am replacing the fuel sending unit, the roll over valves, and the gaskets (seals, grommets or whatever they are called).  Hopefully that will fix it.  I am also changing a bunch of sensors to see if I can get rid of the poor idle, along with new ignition and injectors.  If after all THAT it still runs poorly, I dont know what else it could be!  I will also check all lines to make sure nothing is blocked (actually, I am thinking about replacing all the rubber hoses, just in case; it's cheap to do so, so no harm should come out of it).

In the mean time, I fixed my daily driving issues; I got me a car!

[grumpygy]

On Rubber hoses.  Had on an old MGB I have it would run great for a short time then Just die.  Kept pulling the Carb  and their was bits of rubber in the float bowl. I would clean everything and it would again run great for a short time.

  It ended up being that when I put on one of the rubber line I cut the inside rubber making a flap, As pressure built it would cut fuel flow to the Carb.  Just something else you could  check.