'07 MCS R56 shy of 90k miles
SUMMARY
Car has been cranking but not starting, happens off and on never consistant. Sometimes it starts up just fine(no hesitation) and has been performing great! When it does fail to start the DME relay is clicking and so is something under the intake somewhere. All things kinda pointed towards a HPFP. A shop confirmed the HPFP was only putting out about 110-170psi when it was failing to start. However, I was checking electrical connections I tapped on the DME/ECU and the clicking stopped and i heard a chime from inside the car. I should have attempted to start it right then, but I had the intake off and was cleaning some connectors. So i finished cleaning everything and buttoned it up. On the first attempt it was just cranking but then my buddy wiggled the front most connector that plugs into the DME and the car started right up! I turned it off and started it back up a few times in a row. It was late and I didn't have time to start repeating the issue to confirm it's indeed a DME connection issue. I will be doing that tonight after work.

I will tell the story from the beginning now.

About 2 weeks ago my car cranked but didn't even try to start. Let it sit a couple seconds and then it started just fine. Drove to work and it wouldn't start after work. Let it sit for a bit longer and it finally started after a few attempts. It has been doing it for a couple weeks now. Sometimes starting on first attempt. Has always performed very well once driving. In the mean time I had already been waiting to replace a leaking thermostat hose. Replaced the thermostat while I was at it as well as the oils pressure sensor. Drove great the following day. The day after that it had trouble in the morning but started after a few minutes between attempts. After work that day it wouldn't start at all. Waited and waited, lots of attempts, held pedal down to help clear flooding. A couple times it barely started with zero throttle response and chugging very very bad, one time I did have very slight throttle response and it was revving easier above 2k. Those instances have only happened a couple time out of the 40+ times that it has cranked and failed to even try to start in the past 2 weeks.

The following day I luckily got it to start and I attempted to drive it to a repair shop...upon which it died about half way there. It was performing like normal too but then just complete cut off. As if someone turned off the key. First time it has died on me while driving. After a few attempts and about 30min of sitting in a lot I managed to coast into, it started and I actually got it to the repair shop. I unloaded my personal items and attempted to start it back up, just cranked but no sign of wanting to fire up. The shop ended up having to push it into the bay where they diagnosed the issue has a HPFP going out. Yet it started for them when they went to take it out of the bay. It also started for me when I went to tow it to my friends house, then I just ended up driving it all the way there...then I ended up where the first paragraph explains possible electrical/DME connection issue.

I really appreciate any help trying to give me the confidence that it is actually a connection issue before I go buy a HPFP. Assuming a warrantied HPFP needs to be replaced at a certified Mini repair shop or Dealership. Closest dealer is 400mi from me so I will be replacing it myself. If it's the original HPFP it is outside of the 10year warrant period I guess also.

Thanks

 

After work today I was able to start the car 5 times no problem. I started it once and let it run a bit, shut it off, started back up and then drove it around for a while. It is driving great. Parked and started it up after letting it sit for 5min. Then I started it twice more in succession. I wiggled the plugs on the plugs on the DME and it didn't cause it to fail to start. Part of me was hoping it would fail to start and I could repeat the solution by tapping on the DME or seating the plug better...however if it really was just a simple connection issue I could have already "solved" it when i cleaned the connectors and reseated them. So I plan on starting it up and driving it a bit in the morning and after work tomorrow. Maybe do that Thursday as well, and if it never fails to start I will then drive it regularly. If it does fail to fire up I will obviously tap on the DME or wiggle plugs to see if that allows it to start.

 

Maybe try disconnecting the battery and cleaning the connections

 

Yesterday after work she started right up multiple times and I drove it around for a while with no issues.
It's fairly conclusive that it was a bad electrical connection. Whether it is a plug that goes into the DME or a solder/trace giving out and cracking inside the DME...I do not know for sure. I can't even be positive that the DME connection was the culprit. I have yet to get the car NOT to start again so that I can wiggle or tap the DME and test my theory. Going to drive it to work this morning, assuming it starts. Then check on it at lunch, and if all is good still after work I will drive it home. I live out of town and car has been at friends house in town.

Thanks for the suggestion. That was done when I cleaned the other electrical connections.

 

Issue persists...

Yesterday I grabbed the car at lunch time, started right up so I drove it to work. Again, it drives great when it's driving and it has only died on me once while this issue has been present. Then about 5 hours later it decides not to start. That clicking DME relay is still present when the car stops cranking after it fails to fire, sometimes there is something clicking behind the motor too(down under intake). The car quits cranking all by itself...I don't know how long it's supposed to crank for automagically. Popped the hood and tapped the side of the DME, clicking stopped. Tried to start the car and no go. This time I had to wiggle the front most DME plug to get the clicking to stop. I repeated that 2 more times with no luck getting it to fire. Finally went and got a coworker who wiggled the plug while it was cranking and as soon as he wiggled it, she fired up. This time it was chugging really bad with no throttle response. Thought maybe it had been flooded and sent itself into an weird mode, so I shut it down. Started it back up with the pedal held down and it fired up nicely running great.

Drove it back to my buddies house where 2 minutes after parking it and shutting it down, it didn't want to fire back up. Went back last night and same crap, won't start up unless that front most DME plug is wiggled. If the car would have also failed to fire up after wiggling the plug, I wouldn't be so positive this is the issue. The consistency of my "solution" is pointing to that plug, whether harness side or DME side I don't know. However, I have never been able to kill the car while it's running by wiggling that forward most plug. So if it is a connection issue, it must mean that connection only matters at startup and not once running. Which kinda doesn't make sense to me but I need to see wiring diagram and better understand how the DME works with it's I/O.

I'm going to try and inspect the female(harness side) connections with some good light today and there might be a damaged one, or one that is getting loose. Male pins on the DME look fine.

 

Going to inspect things farther today.
I've been driving the Mini and it still fails to fire up often. I've figured out that it will fire up every time when pushing the DME front most plug to the right(sitting in for orientation). I had a coworker pull the plug to the left and nothing ever happened. There is a little plactic piece that the rear 2 DME plug leads are zip tied to. The plug giving me the issue wasn't zip tied so I zip tied it to the right against the plactic piece and car has started every time so far. See how it goes after a few days or so. Not a permanent solution but cheaper and easier than a new harness or DME.

 

I had similar problems like yours.
One day car will run perfectly, then another it will stall anytime during a drive.
Sometime it refuses to start, but started after a few attempts.

Thought its the HPFP's fault, so i ordered a new one and changed it out, within 10 min the engine stalled again, so i suspect it has to do with fuel delivery issues. Checked on the in-tank fuel pump works perfectly, but there is no proper 12v+power supply to the fuel pump !

So after hours of wiring tracing and trobleshoot, the culprit was found to be the relay that was hidden inside the footwell fusebox assembly. There is NO fuel pump relay that user can changed out on the N18, this elusive fuel pump relay is soldered internally as part of the fusebox assembly.

To cut the story short, i changed out the footwell fusebox, and it worked well till now.

Expensive lesson learnt, its not always the HPFP's fault !

I opened up the faulty fusebox and found out the fuelpump relay soldered on the PCB were of lower current capable kind (not the usual automotive 30A type), it will last you sometime , and you know it will failed again in future.

Mini is such a nice looking car, fun to drive but NOT reliable !

 

I even changed the fuel pressure sensor, suspecting that the DME cuts out the relay due to a faulty fuel pressure sensor. Yet still the engine dies off anytime it wants to! A voltage check across fuel pump revealed sub 12v-'ish and erractic voltage range from 2~8v +dc. I then decided to jumper +12v from batt directly to the fuel pump and it works. The car can be driven for days with this config. It proves that there is nothing wrong with the HPFP, LPFP and the fuel pressure sensor.

I bit the bullet and ordered a new foot well fuse box assembly.... and voila! Car is running fine!

Current Amp drawn is 12A and with that small tiny relay soldered inside the fusebox, it's not going to last very long.

 

At this point im positive it isn't a HPFP issue. Car has started every time now since I zip tied the plug leads to the side. I've reproduced the issue and solution at least 20times. At this point it's just figuring out whether it's a connection or crimp failing inside of that huge plug, or on the DME side.
I've looked up the harness and I believe that plug belongs to the main harness. The other 2 plugs belong to the engine bay harness. I would like to check continuity from the wire side to the DME pins but not sure how to go about that yet. I don't know if I can reference chassis ground and then probe the wires and hope to find an open circuit than is completed when I push the plug to the side. Visually everything is fine.