Start up problem
 

Hi ! I hope you're doing good. I have a question for you with reference to a strange behaviour that I'm experiencing with my 1999 Rover 75. I have recently changed its battery, and now I am difficulties to start up the car. I noticed that, when I turn partially the key, before actually trying to start, there is a buzz that lasts a few seconds, though not every time. Sometimes the buzz is absent, and that's when the car does not start up. What could this be? A fault in the alarm system, perhaps? I also thought that perhaps I could reset the car computer when the start up failure occurs, though I don't know how to do this. Any help would be greatly appreciated! Kind regards, Vincenzo

Sounds like the buzz is the low pressure under bonnet fuel pump, and if you can't hear that then the car won't start. Could be a failing pump, so next time it happens lift the bonnet and give the pump a few taps to see if it starts running - it sits just inboard of the battery.

The LP fuel pumps shuld run for around 30 or 60 seconds with key to position II, depending on the ECM.

If the pump is good then search for plenum chamber checks on here to see if your ECM has gone for a swim.

When the pump doesn't run check that your oil pressure light has lit up like it should with key to position II, and also if you have an automatic then does the display show the correct position of the gear lever or does it show EP?

As Mike says try the above pic below.
https://i.imgur.com/D3kfNQhl.jpg1