The mechanic today diagnosed my car rail pressure with roughly around 15 psi (1.5 bars) and it should be around 30-40 psi (2.5-3 bars). He told me that it could be fuel regulator, fuel pump or fuel filter. All these parts and labor is very expensive. So my bet is on fuel filter, so can an old fuel filter be responsible for such a drop in pressure?

The symptoms for my car is that it takes 10-12 long cranks for car to start, BUT once started it runs fine. Which even makes me wonder why does it even runs fine when supply pressure is low but takes tremendous effort to start!

The car is 2011 mini cooper base model N12 engine.

  • It's very unlikely to be the fuel filter, fuel filter problems get worse as fuel demand increases, if you had a clogged fuel filter you'd be having a lack of power at higher RPMs. As you say your problems are in starting, not running, this limits the options.
    – GdD
    Nov 7, 2022 at 9:08
  • @GdD alright it makes sense. But what doesnt makes sense is why car runs fine after startup and no hesitation while acceleration?
    – user74015
    Nov 7, 2022 at 19:28

1 Answer 1


Both the fuel pump and the filter are inside the fuel tank and are accessed via a panel under the rear seat. So as long as you're in there it would be easy enough to replace the filter, re-install, and then see if that solves the fuel pressure problem.

If not, then replace the pump as well since it's already mostly exposed.

The regulator is under the hood but is somewhat buried in there.

I agree, it could be any of these. If this were mine, I'd probably start with the filter.

  • I thought those models come with regulator inside the fuel pump itself and not under the hood. The engine he specified N12, there is no HPFP
    – user0193
    Nov 7, 2022 at 9:45
  • Alright I had same reasoning, so eventhough if it turns out to be fuel pump issue and not fuel filter, having it replaced anyways is a good idea considering how old is the car. Also what dont makes sense that after starting it accelerates fine and no hesitation there!
    – user74015
    Nov 7, 2022 at 19:30

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