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516 Posts
I have a simple question and a more complicated question.
1. There are 3 lines that go from the back to the front of the car. One white, one green, one black. I know that these are for. Black is a fuel line coming off the fuel filter and to the fuel rail. White is the EVAP purge line going to the N80 valve. Green line goes to a vacuum port. My question is:
What exactly does the green vacuum line do? I know basically how the fuel tank works. It has valves in it that release vapor to the N80 through the charcoal canister. I know that the tank must maintain a specific pressure to work correctly so I'm assuming the EVAP purge keeps vacuum balanced as fuel is used and heat rises. I just don't understand what the green vacuum line controls. Can someone please explain that to me? (Maybe the leak detection pump?)
2. The more complicated question. Can someone explain to me how the valves in the fuel tank work? I have replaced the valve that was faulty do to the recall when these cars very first starting having "hiccups". It had never been done on mine, so I ended up doing it. Now I don't have fuel spewing out my fender well. However, when the car heats up the fuel pump starts going haywire, I can hear it and have felt it doing it when it happens - it surges and sounds like it sucking up air. I'm pretty certain it's too much vacuum in the tank as the fuel is drawn out and this starves the fuel pump (I have observed on VCDS a fuel trim scenario that supports this theory as it goes lean when it's happening and the computer pulses the injectors to increase fuel). I have replaced the fuel pump with a stock unit and now it has the DW high pressure pump installed so it's not the pump. Which leads me to believe there is a restriction somewhere. When I did the recall I replaced the charcoal canister and blew out the lines (I'm going to blow out the lines again just in case I didn't get it all and that's where the restriction is). Otherwise I have a feeling it's one of the other two valves I didn't replace during the recall. I didn't replace them cuz my understanding is they aren't the same as the one I replaced and I can't just get the other valves. Also the tank is no longer available or I'd just replace the whole thing. Can anyone explain exactly how the fuel tank in the R32 MK5 works? I'm especially curious about the valves in the tank. Maybe this is a question for the Humble Mechanic but I'm assuming someone around here has to know, like a master tech or just a real smart guy like Grogory on MK4s.
Thanks!
1. There are 3 lines that go from the back to the front of the car. One white, one green, one black. I know that these are for. Black is a fuel line coming off the fuel filter and to the fuel rail. White is the EVAP purge line going to the N80 valve. Green line goes to a vacuum port. My question is:
What exactly does the green vacuum line do? I know basically how the fuel tank works. It has valves in it that release vapor to the N80 through the charcoal canister. I know that the tank must maintain a specific pressure to work correctly so I'm assuming the EVAP purge keeps vacuum balanced as fuel is used and heat rises. I just don't understand what the green vacuum line controls. Can someone please explain that to me? (Maybe the leak detection pump?)
2. The more complicated question. Can someone explain to me how the valves in the fuel tank work? I have replaced the valve that was faulty do to the recall when these cars very first starting having "hiccups". It had never been done on mine, so I ended up doing it. Now I don't have fuel spewing out my fender well. However, when the car heats up the fuel pump starts going haywire, I can hear it and have felt it doing it when it happens - it surges and sounds like it sucking up air. I'm pretty certain it's too much vacuum in the tank as the fuel is drawn out and this starves the fuel pump (I have observed on VCDS a fuel trim scenario that supports this theory as it goes lean when it's happening and the computer pulses the injectors to increase fuel). I have replaced the fuel pump with a stock unit and now it has the DW high pressure pump installed so it's not the pump. Which leads me to believe there is a restriction somewhere. When I did the recall I replaced the charcoal canister and blew out the lines (I'm going to blow out the lines again just in case I didn't get it all and that's where the restriction is). Otherwise I have a feeling it's one of the other two valves I didn't replace during the recall. I didn't replace them cuz my understanding is they aren't the same as the one I replaced and I can't just get the other valves. Also the tank is no longer available or I'd just replace the whole thing. Can anyone explain exactly how the fuel tank in the R32 MK5 works? I'm especially curious about the valves in the tank. Maybe this is a question for the Humble Mechanic but I'm assuming someone around here has to know, like a master tech or just a real smart guy like Grogory on MK4s.
Thanks!