Maybe the fuel pressure regulator needs changing. I can imagine it changing its whine when a new pump is fitted as the pressure going into it might change
Just my 2p
Just my 2p
I'm confused about why the pump would need to run constantly ONLY when the engine is running. If there was a leak in the pressurised system then surely it would leak all the time, (and thus cause the pump to run all the time), not just when the engine is running??.
Firstly the initial running of the fuel pump to prime of the fuel rail when you turn on the ignition is a timed function controlled by the Motronic. It’s a dumb system, So even if you had a fuel leak, the pump would still only run briefly.
(If there were an electrical fuel pressure sensor in the system, then the fuel pump could be controlled to run to replace the lost pressure, but there isn’t.)
Secondly when the engine runs, the fuel pump will run constantly. The pressure in the fuel rail is maintained by the pressure regulator which passes excess fuel back to the tank.
Hope this explains.
Ian
Maybe you don't need to rush to change it, mine has been singing for months (I know, I know, once the house painting has finished I will get round to checking it), doesn't seem to have affected the running at all. I did look at the fuel pressure regulator, well I looked for it in Haynes, which doesn't mention it all, got as far as remove gearbox cover in the Clymer manual and realised it wasn't going to be a quick job!
I promise I will follow the advice given so far before asking any more questions.