Hello,

Hello! You're right, the P15DF code combined with misfire codes (P0300-P0304) on a 2011 Mini Cooper S strongly suggests a High-Pressure Fuel Pump (HPFP) issue. Let's break down why and what you can do:

Understanding the Codes:

P15DF (Fuel High Pressure System, Pressure Too Low): This code directly indicates a problem with the high-pressure fuel system, specifically a lack of sufficient pressure.
P0300 (Random/Multiple Cylinder Misfire Detected): This means the engine is misfiring, but the computer can't pinpoint a specific cylinder.
P0301, P0302, P0303, P0304 (Cylinder 1, 2, 3, 4 Misfire Detected): These codes confirm misfires in each cylinder.
Why the HPFP is Likely the Culprit:

The HPFP is responsible for delivering fuel at very high pressure to the direct injection system. If it's failing, it can't maintain the necessary pressure, leading to misfires and the P15DF code.
The hard starts and rough running you're experiencing are classic symptoms of HPFP problems.
The fact that it started happening after the shop worked on the timing chain and HPFP seal is very suspicious. It is possible that the seal was not installed correctly, or that the pump was disturbed during the repair.
Troubleshooting Steps (Before Replacing the HPFP): 

Check the Low-Pressure Fuel System:   Official Site


While the high-pressure side is the primary suspect, a weak low-pressure fuel pump or a clogged fuel filter can also contribute to fuel delivery issues.
It is less likely, but should be ruled out.
Inspect the HPFP Sensor and Wiring:
A faulty sensor or damaged wiring can provide incorrect readings, triggering the P15DF code.
Visually inspect the wiring and connector for damage.
Check for Fuel Leaks:
Although less likely to cause all those misfire codes,

Hi All,
 I am sure this has been aske a million time but, the P15DF code is present on my 2011 Mini Cooper S and has permanent codes of P0300, P0301, P0302, P0303 & P0304. I have been troubleshooting this with what tools I have and research points me to the HPFP. Runs and starts but occasionally it will hard start and run rough. I wanted to bounce this off those who have experienced P15DF code that indeed this is the HPFP and if so,  before I gamble $750 USD on the HPFP. I think its that everything seems to point to that. I recently had a shop replace timing chains and camshafts, they also replace a seal around the HPFP? and not long after maybe a 2-3 months later it popped up and keeps popping.

Again new to the site sorry if this repetitive. Also dumb question is there a cheaper alternative to this HPFP? Probably not but, thought I'd ask. Thank you for everyone's time. 

Stewmini