raudiowdy
09-03-2024, 06:16 PM
Hi all,
I'm a longtime lurker but novice poster, so apologies if this is in the wrong place--just let me know. I just got my 2015 S4 back following a complete DSG replacement at 102,000 miles (a thread for another time). I decided that the best way to welcome her home would be some TLC--a thermostat, water pump, PCV, carbon clean, and valve cover gasket replacement. The PCV requires removal and reinstallation of the high-pressure fuel lines, which didn't seem too bad. I was careful cracking them loose, and I torqued all of the connectors to spec when I reinstalled them. I also replaced the injector O-rings when I pulled the fuel rail/tumble flap assemblies for carbon cleaning. Every DIY seems to recommend unlocking the car and opening the driver door to prime the HPFP after this to check for leaks (makes sense). When I did this yesterday, I heard the usual fuel pump whine (maybe a little more "burbly" than usual, which I attributed to air in the lines.) I didn't see any leaks or smell any fuel. I wanted to double-check today before I reinstall the supercharger, and I can't seem to get the HPFP to prime again. It's been over 24 hours since the first prime, but no matter what I do I can't get the usual pump whine to happen when I open the driver door. I did leave the battery disconnected overnight, I'm not sure if that makes a difference. The way I see it, there are two possibilities:
1. I did such a phenomenal job re-sealing the high-pressure fuel system that it's holding pressure perfectly, and the HPFP isn't priming because the rail is already at operating pressure. I do work on high pressure/vacuum systems for a living, but...I'm bearish on this being the case.
2. I broke something and the HPFP is out of commission.
Does anybody have any thoughts on what might be going on? Is there a way to bleed the high pressure fuel system that I don't know about? I'm inclined to believe option 2 unless someone tells me otherwise. I'm going to check the pump fuse/relay/etc. tomorrow, but I'd love to know if I'm being paranoid over nothing. Thanks in advance!
I'm a longtime lurker but novice poster, so apologies if this is in the wrong place--just let me know. I just got my 2015 S4 back following a complete DSG replacement at 102,000 miles (a thread for another time). I decided that the best way to welcome her home would be some TLC--a thermostat, water pump, PCV, carbon clean, and valve cover gasket replacement. The PCV requires removal and reinstallation of the high-pressure fuel lines, which didn't seem too bad. I was careful cracking them loose, and I torqued all of the connectors to spec when I reinstalled them. I also replaced the injector O-rings when I pulled the fuel rail/tumble flap assemblies for carbon cleaning. Every DIY seems to recommend unlocking the car and opening the driver door to prime the HPFP after this to check for leaks (makes sense). When I did this yesterday, I heard the usual fuel pump whine (maybe a little more "burbly" than usual, which I attributed to air in the lines.) I didn't see any leaks or smell any fuel. I wanted to double-check today before I reinstall the supercharger, and I can't seem to get the HPFP to prime again. It's been over 24 hours since the first prime, but no matter what I do I can't get the usual pump whine to happen when I open the driver door. I did leave the battery disconnected overnight, I'm not sure if that makes a difference. The way I see it, there are two possibilities:
1. I did such a phenomenal job re-sealing the high-pressure fuel system that it's holding pressure perfectly, and the HPFP isn't priming because the rail is already at operating pressure. I do work on high pressure/vacuum systems for a living, but...I'm bearish on this being the case.
2. I broke something and the HPFP is out of commission.
Does anybody have any thoughts on what might be going on? Is there a way to bleed the high pressure fuel system that I don't know about? I'm inclined to believe option 2 unless someone tells me otherwise. I'm going to check the pump fuse/relay/etc. tomorrow, but I'd love to know if I'm being paranoid over nothing. Thanks in advance!