My mini starts very rough and the RPMs run up and down (200-2000), it stalls once or twice. At this time
the fuel pressure is around 70-80 PSI. After a few starts it smooths out, I let the engine warm up to 180+
degrees, I can now shut the engine off, pull out the key, reinsert the key, start it up and my fuel pressure is now
at 700-750 psi. At this point, the car drives like new with all the power and no sign of any fuel delivery problem.
I let it sit for two hours and the problem returns, it is worse the longer it sits, but it all goes away when the car
reaches running temperature the next time I start it up. I have installed a brand new HPFP and it is exhibiting
the very same behavior, hard to start, but then runs great when warm. Is there something else going on other than
the high pressure fuel pump?

 

Did you purchase a quality OEM HPFP, or one from Amazon or Ebay? The cheap ones are notorious for having issues, even right out of the box.

 

Yes, I purchased the pump from Ebay. It is the second pump that I have purchased that cold-starts poorly, each were a "good deal". The first I purchsed on Amazon and managed to return it and get a refund. I will do the same with this one. Why does this one and all the pumps, including my original OEM pump, work perfectly when the engine warms up? Also, at altitude above 5,000 ft. my car starts with no problem, first thing in the morning.

 

There is a temperature circuit in the pump that compensates for rising temperatures. No one "really" understands how it works, or why it fails, except the original designer. There is a whole thread here (somewhere) that goes into the pump and failure modes, if you feel like reading....

 

I bought one from AliExpress and now I'm having the same cold starting issues I was before I replaced it. I'll be replacing the in-tank pump and then if that doesn't work then it will be back to the HPFP.

What doesn't help is the simply insane pricing on the genuine articles - all the replacement guides and threads I read seem to have been from a time when they were $200 USD a pop. Now they are $500 - all the way up to $1,200 USD.

 

Did you ever find out the issue? I have been experiencing the exact same issue for TWO YEARS! The car never starts first time, always takes anywhere from 2 to 50 tries to start, And it gets worse the longer it sits. When it’s finally started it runs beautifully. Ive already changed the hpfp. The car has been just sitting in my driveway for a very long time from this stupid issue.

2011 cooper s n18

 

https://www.northamericanmotoring.co...fuel-pump.html

HPFP or low pressure fuel pump

On the N18 it is listed, watch the split year on the design change. Dont get the N14 one for the HPFP as thats not your engine.

 

Hi, i have already put in all new OE hpfp, lpfp, sending unit, vanos solenoids, plugs and coils. All of this is very recent.



experiencing the same issue. Im thinking it might be the fuel pump relay thats soldered on to the jbe, or the valvetronic actuator motor…

you recommend anything else i should inspect, or try?

 

If anyone has an idea as to what might be going on with my car, please let me know. I am thinking it might be a compression issue, it’s the first thing i should have checked before throwing all these new parts on… i have a compression tester but not a leak down tester