_ethrty-Andy_ 2122 Report post Posted January 1, 2015 Ok so this in on my V12 E34, but will be the same as any other car I am sure... only difference is there is two of everything When i leave the car for any period of time more than about 12 hours, the car takes ages to start, there is no fuel, to either bank. after cranking for long enough, and i assume enough fuel pressure builds up, it starts up good as gold. Once running, i have full engine power at my disposal etc, its not running lean or rich, i am familiar with usual fuel pump failure symptoms etc. Turn car off and then come back to it in an hours time or whatever it starts straight up like it always should. Almost like fuel pressure is dropping over night???? There is no evidence of leakage both visually or smell All 12 fuel injectors are recently refurbished, very unlikely to be leaking already, and has run fine on them before now. Quote Share this post Link to post Share on other sites
allan 295 Report post Posted January 1, 2015 (edited) Andy just a stab in the dark does it have a bleed valve or pressure regulator valve of some sort at all on the fuel rail. If so this could be releasing the pressure built up by the pump and allowing the fuel to drain or siphon back. Edited January 1, 2015 by tim 325 Quote Share this post Link to post Share on other sites
_ethrty-Andy_ 2122 Report post Posted January 1, 2015 Andy just a stab in the dark does it have a bleed valve or pressure regulator valve of some sort at all on the fuel rail. If so this could be releasing the pressure built up by the pump and allowing the fuel to drain or siphon back. yep got two of them one for each bank, they are original as far as i know. rekon they could both throw the towel in at the same time? Quote Share this post Link to post Share on other sites
allan 295 Report post Posted January 1, 2015 If vacuum controlled one or both could have sprung a leak just a thought. Quote Share this post Link to post Share on other sites
euroriffic 603 Report post Posted January 1, 2015 (edited) My ute does this too, but it has a mechanical fuel pump and is carby. Pita! Also can you hear the pumps do their start up prime before you turn it over? Or do the even do that? Edited January 1, 2015 by euroriffic Quote Share this post Link to post Share on other sites
_ethrty-Andy_ 2122 Report post Posted January 1, 2015 My ute does this too, but it has a mechanical fuel pump and is carby. Pita! Also can you hear the pumps do their start up prime before you turn it over? Or do the even do that? yes they prime etc, but i think all the fuel gone back to the tank, empty lines Quote Share this post Link to post Share on other sites
Allanw 1052 Report post Posted January 1, 2015 Next time, cycle the ignition 5 or 6 times to prime the lines. On cars I've had that dropped the pressure, you could hear the pump pitch change when it reached pressure. If there is no air, it should only take a couple of seconds of pump run time. Does it use a single coolant temp sensor for cold start enrichment? Quote Share this post Link to post Share on other sites
Young Thrash Driver 1020 Report post Posted January 1, 2015 I think it's fairly well documented that the V12 makes petrol disappear. You could consider an M44 conversion? 1 Quote Share this post Link to post Share on other sites
allan 295 Report post Posted January 1, 2015 This any help http://workshop-manuals.com/bmw/7_series_e38/750il_m73_sal/2_repair_instructions/13__fuel_system_%28m73%29/31__fuel_pump_with_drive_and_line/2_ra__notes_on_fuel_pressure_check_%28reference_pressure__intake_manifold_pressure%29/page_801/ Quote Share this post Link to post Share on other sites
