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On 18 Dec 2005 at 22:42, Constantino Tobio wrote: > That makes a lot of sense- one thing, though. The car was running maybe > 15 minutes before I put it on the flatbed, and it was fairly chilly. If it was just idling the whole time that would surprise me, too, but maybe there's something wrong with the cooling system, like a missing bellows or rust- thru somewhere. A lot also depends on one's definition of "fairly chilly" and one's perception of time can also get distorted when you're in the middle of something. At least that's what my wife tells me.... ;-) > The pressure regulator is designed to shut if pressure drops beneath the > set pressure, and this is a pretty bulletproof device. So, with the pump > not delivering fuel, it can be assumed that this valve stays shut. The > only way for fuel to then get sent back into the tank is via the pump. Either valve will be overcome if the pressure exceeds the limit of the valve. The pressure limit of the regulator is it's set point (~30 psi) while that of the pump is about 20 psi, so the usual route would be thru the pump valve. If both valves are working, holding 20 psi on the gas will raise it's boiling point somewhat, but I don't know how much. If the rubber tip on the pump valve is cracked then it's possible that it lets the gas depressurize, lowering the boiling point. This is one possible explanation as to why this problem seems worse on some cars. It's interesting to note that Mercedes had this problem in their D-Jet cars and they put out a fix for it. The M-B fix was to remove the regulator and reach in the side port with a drill and drill a 1mm hole in the central stem. This made a permanent bypass in the system, but the pump has plenty of capacity to provide the extra flow. The point of the hole was to allow fuel to boil and move back to the tank, but allow gas to flow up to the engine again once things cooled down. In effect it provided a "leak" which admitted gas instead of air as the engine cooled back down and the fuel vapor condensed. I've never tried this fix, because I thought that a 1mm hole was pretty large and I was afraid of breaking off a drill bit if I went smaller. Someday, I'd like to try to make a pilot for a small drill so I could hold it centered while drilling, and, hopefully, drill a very small hole, maybe .010-.015" in there. In the meantime, the fuel pump primer pushbutton is a lot easier to do. -- Jim Adney jadney@vwtype3.org Madison, WI 53711-3054 USA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~