[Bubbaspaarx]

Hi all,

Long story short, I got a HPFP replaced after it dismantled itself and I don't think the company who carried out the repair did it properly. I've exhausted my patience asking them to fix it so I'm doing this next part myself.

Car is still driving fine and have actually covered nearly 5k since it was done. The issue is that the system loses pressure when off so turning the car on can take a second or two before it fires (which leaves errors) and booting the car at peak torque will throw drivetrain errors or turn the engine off entirely. Between those two things though, it's never driven better.

Assumption is that the one or more of the injectors have crap in them from the dodgy repair and they are unable to fully close hence the loss of pressure. Can't be certain though.
A local engineer told me to take the return pipes off the top of the injectors and see if any fuel comes out during turn over.. apparently there shouldn't be any at this time. Tried last night and am not sure if they are or aren't. Turn over doesn't last long enough to say for certain. I'll upload vids though and just want to know if anyone spots anything particular.

The errors with WOT are def pressure related. I tracked it on bimmerlink and under normal/low load the pressures are fine but right at the top it's not high enough. At turnover I believe it needs 300psi and it drops well under that and therefore needs a few turns before it builds that kind of pressure.
TIA

[Watsey]

Hopefully Enabled will add his words of wisdom.

In the meantime, have you done any easy/simple maintenance processes such as adding a high concentration cleaner to your fuel to try to remove residues from injector tips ?

Is there any evidence of injector blow-by via the injector/head threads ?

You may have mis-typed in your original post but the diesel rail/injector system operates at a far higher pressure than 300psi. I'm not sure where you got that value from.

[Bubbaspaarx]

Originally Posted by Watsey

Hopefully Enabled will add his words of wisdom.

In the meantime, have you done any easy/simple maintenance processes such as adding a high concentration cleaner to your fuel to try to remove residues from injector tips ?

Is there any evidence of injector blow-by via the injector/head threads ?

You may have mis-typed in your original post but the diesel rail/injector system operates at a far higher pressure than 300psi. I'm not sure where you got that value from.

Thank you for the response.
I've not checked for blow-by as I'm not entirely sure how I would do this? Happy to give everything a go at this stage.

The 300bar (sorry not psi) i believe is the minimum pressure required to get the engine started. I understand they generally go up to 1800bar and are limited to 2100bar.

I'll attach a couple of screen recordings of the values

[Bubbaspaarx]

Motorway travel to WOT. It crashes the app as I get the drivetrain error. Something off with the control deviation figure

Crawling before parking the car and engine off

[Enabled]

Every time I've changed an injector on these N47/N57, the rail wasn't at any high pressure remaining, meaning the fuel did not squirt out violently. The HPFP has to generate that minimum starting pressure within the first few cranks.
Rail pressure is regulated via both the metering unit (pump control) on the HPFP and the rail pressure control valve as well.

If either of those two are contaminated or stuck, then it will have a hard time building the initial pressure. The low pressure fuel pump (in-tank) also contributes to how quickly the HPFP works.

If this car had a fuel pump event, this is often due to water or other contamination. How are the metering unit, rail control valve, rail pressure sensor, and LPFP looking?

Normally I would start with an inspection there.

[Bubbaspaarx]

Originally Posted by Enabled

Every time I've changed an injector on these N47/N57, the rail wasn't at any high pressure remaining, meaning the fuel did not squirt out violently. The HPFP has to generate that minimum starting pressure within the first few cranks.
Rail pressure is regulated via both the metering unit (pump control) on the HPFP and the rail pressure control valve as well.

If either of those two are contaminated or stuck, then it will have a hard time building the initial pressure. The low pressure fuel pump (in-tank) also contributes to how quickly the HPFP works.

If this car had a fuel pump event, this is often due to water or other contamination. How are the metering unit, rail control valve, rail pressure sensor, and LPFP looking?

Normally I would start with an inspection there.

As far as I can see, the low pressure pump is working fine (3.9bar), but not sure about the other parts. I did do a full diagnostic through ISTA not long ago and it passed with flying colours. Surprised me too.

The car has done 210k miles so I think the pump may have failed mainly due to age/wear rather than anything specific. Happy to check other things though.

It does seem that the injectors aren't working as well as they need to be. The original set were checked after and the tester only charged me half the money as they were so bad. All 6 were leaking/back leaking.

[LBS]

I probably won't be able to give you much advice, but I did an engine overhaul on my 335xd and for over a year I've been solving the problem where the first cold start has an erratic run, which stops after about 2 minutes and then everything is fine. we have replaced almost every part on the engine, it cost me a lot of money, but the problem still persists

[bmwPower99]

Originally Posted by LBS

I probably won't be able to give you much advice, but I did an engine overhaul on my 335xd and for over a year I've been solving the problem where the first cold start has an erratic run, which stops after about 2 minutes and then everything is fine. we have replaced almost every part on the engine, it cost me a lot of money, but the problem still persists

I've had this and it was unmetered air issues (intake leak in my case but it could be anything) which seemed to calm down when the engine was warm.

[LBS]

Can you elaborate on that? So, in your case, was the problem with a faulty air sensor, or did you have a leak somewhere?

[bmwPower99]

Originally Posted by LBS

Can you elaborate on that? So, in your case, was the problem with a faulty air sensor, or did you have a leak somewhere?

My egr cooler was faulty allowing overly hot gases into the plastic intake causing a hole.