N18 High Pressure Fuel Pump (HPFP) - Rail Pressure

[Sf1970]

A few days ago my standard N18 engined R56 JCW, registered Sept 2013, started to splutter and the half engine light illuminated. After stopping the engine and restarting it went away.

How it happened might be a red herring, but does give me slight hope it might not be the dreaded HPFP issue. I was joining a motorway on a very tight left hand curve, which results in the car turning tightly for around 8 seconds. My fuel light was already on and I’m aware the low pressure fuel pump is located in the nearside of the fuel tank, so wondering if I got fuel starvation momentarily and therefore a lack of feed to the HPFP. Grasping at hopeful straws possibly there???

Upon getting home and for the whole journey it ran faultlessly, I read my fault codes and they indicated low fuel rail pressure. I cleared these and they have since not returned.

I’ve had no further issues and now continually monitor the LPFP output pressure and the HPFP output rail pressure on my Bimmerlink app. Low pressure reading a constant 98psi and the rail pressure between 1100 and 2200psi. Not once has it dipped. After having a HPFP failure on another R56, I do know they usually fail intermittently, so this may be the case again.

Online guidance would suggest both my low pressure and rail pressures are higher than spec, standard are 85psi and between 750 and 1750psi respectively. Albeit, I have found evidence to suggest later model N18 engines had their rail pressures increased to 1100psi at tickover.

Just wondering if anyone with a later N18 engine has measured their pressures please?

I’m also wondering if I’m getting false readings as I doubt both pumps are out of spec. I do however think my HPFP may be on its way out, just confused by my readings.

Thanks in advance.

Edited by Sf1970 on Saturday 2nd November 10:58

[CoolHands]

I looked at mine once (also in bimmerlink) and it is quite confusing as had very wide range. Mine ranged when driving from 47 bar up to 98 bar (1421 psi). That is for ‘rail pressure’ which as far as I could find out was the right one to choose. Mine is 2013 N18 so a late one.

[Sf1970]

Fabulous, thank you. Maybe mine a little high then

[CoolHands]

I remembered to take some more pics this morn for future reference ; car was reasonably warm at this point ie not immediately after start up

Idle seemed to be 72-78bar



Full throttle 2nd gear light load high revs at time it was snapped, 152bar:



Full throttle 4th gear low revs high load 130bar:

[Sf1970]

Amazing, thank you for sharing that. That’s 2175psi. Very similar to mine and more than the quoted 1750psi max. I’m content mine is not over pressurising now, thanks again.