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On 1 Sep 2006 at 20:48, Arkady Mirvis wrote: > My car is being prepared for driving after sitting on stands for close > to 15 years. All hoses are new, of highest quality, recently installed > and secured with Oettiker hose clamps. I've had cars that did this, also with all new, good quality, hose and Oettiker hose clamps, and even NEW injectors. It didn't help. My GUESS is that it has something to do with the quality of the seals in the fuel pump check valve and the pressure regulator. See below.... > I suspect that what you call "air " is actually gasoline vapors. No > wonder, given the temperature in the engine compartment! Gasoline may > boil (vaporize) in hoses after the car was driven and the temperature > in the engine compartment did reach high levels. But gasoline vapors > must condense with the engine cooling off. This confirms by your > suggestion to restart the engine 3-4 hours after driving. You're exactly right, I was simplifying. The gas boils, producing gas vapor which takes up much more volume, meaning that the vapor has to go somewhere. It leaks out the injector tips, hose connections, fuel pump check valve (which will actually let it out to keep the pressure from going above ~20 psi) and forward thru the pressure regulator. Vapor which pushes out the fuel pump or regulator bubbles back up inside the gas tank, but at this point it wouldn't be vapor anymore, because the gas tank is so much cooler. So it just rejoins the gas in the tank. Later, as the engine cools down, the vapors that remain condense back into gasoline, but there's not enough vapor to fill the lines with gasoline, so a vacuum develops. Once there is a vacuum, something will leak in to fill that vacuum. Gas can leak in thru the fuel pump check valve and the pressure regulator and air can leak in thru the injector tips (and internal seals) and the hose connections. My theory is that cars with really good fuel pump check valves and pressure regulators will suck in air, while cars that have very small leaks in those valves will suck in gasoline. So it is the "imperfect" cars which have the starting problem. > My question " is this a common problem?". Volkswagen AG should have > confronted this problem in cars used in hot climates and should have > come up with a solution. Well, I never heard of a VW solution, but I heard from Bosch that Mercedes came out with a fix for this. (Look at a cross section of the pressure regulator to understand this.) They suggested that you remove the pressure regulator and drill a 1mm hole in the central stem, passing the drill bit down thru the regulator INLET and into the stem. The explanation was that this caused a leak thru the regulator, but that the pump had more than enough capacity so the leak would never be noticed while running. After shutdown, the system pressure will fall to zero right away and the gas will all boil, but no gas will be forced backwards into the supply line, so the supply line stays full. Once the system cools a bit and the gas tries to condense, there is free flow backwards thru the hole in the regulator allowing the engine fuel volume to refill with liquid gasoline. This free flow prevents the formation of any vacuum significant enough to suck in air. If you try to restart while the engine is still hot and the engine fuel volume is still full of vapor, then at least the supply line is still full and the pump is running instantly at full capacity, which will fill the fuel ring quite quickly. I've never done this, because it seemed like a lot of trouble and a good way to ruin a perfectly good regulator with a broken drill bit. Someday, however, I'll make a suitable drill bushing and try it. > The engine is enclosed in a very tight space with no provision for any > ventilation (draft). The heat is trapped and everything is left > cooking. It is this cooking which deteriorates everything in the engine > compartment, particularly rubber and caused destruction by fires of > thousands of T3 cars. I don't think the "heat soak after shutdown" is much worse in our cars than in any other, but the rubber fuel lines were certainly a problem. And having expensive injectors which appeared to have non- replaceable hose pieces on them probably led lots of people not to get them fixed when they should have. I hope you replaced all the little hose bits on your injectors when you replaced the rest of the hoses. > Did anyone come up with a solution to ventilate the T3 engine > compartment? To the best of my knowledge, you're the first person who's even thought of the possibility. I really don't worry about it. I just keep an eye on the condition of things in there and replace the hoses when they need it. I used to just replace the ones that leaked, but I found that this generally took me all day and I ended up doing the whole engine compartment anyway. So now I just replace every fuel hose in the engine compartment as soon as one of them springs a leak that's caused by a "dead" hose. I've been "burned" more than once by that "one little piece" of hose that didn't get replaced because it still looked fine. -- ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~