[swellengear]

My experience in rebuilding my HPFP. I have been running the rebuilt unit for over a year with no issues.

**This worked for me, and is in no way a silver bullet to fix any and all HPFPs

Fault finding:

1) You can measure the depth of the diaphragm from the outer edge. If its anything above ~20mm it has lost its oil. (if it's completely empty it will usually measure 27mm from the outer edge) This is usually caused by the rotary seal on the shaft failing. You will need a 22mm X 11mm X 7mm high pressure rotary oil seal.


2) If you open the pump, and it is filled with a mixture of oil and fuel, then one of the o-rings on one of the 3 bellows has gone bad. These can also be replaced with a 20.35mm(ID) X 1.78mm o-ring.

3) Another point of failure (rarer) is a split in one of the bellows. Have not been able to source these, but if you have several pumps lying around you could use a good bellows from another donor pump.

Replacing the Rotary Seal:

Firstly you will need to remove the hpfp. Once done, clamp firmly in a vice, taking care not to damage any bits on the pump.


Once clamped, remove these three torx screws. *take note - some fluid will leak out, so have a couple of rags handy.



IMPORTANT - if the fluid coming out of the pump stinks of fuel, one or more of the o-rings on the bellows have failed and will need to be replaced.

Once the pump is apart, clamp the pump like so:


Place a screwdriver in the slot below, and strike counter-clockwise with a hammer until the cam is loose


You should now be left with this:

Push the rotary seal (in red out, and discard)

The other end of the pump will look like this:


Give everything a good clean with some brake cleaner or similar.

Next, reassemble everything in reverse order - but don't install the cam gear or the new rotary seal yet.
Should look like this:


So next, you want to apply some vacuum to the diaphragm. I found some clear hose lying around which fit snuggly into the diaphragms hole, and just sucked on it a few times to create a strong vacuum on it. I then clamped the pipe to hold the vacuum while I refilled the pump. (a mighty vac or similar would probably do a better job, but I didn't have one to hand)



Next, find a suitable bolt that threads into the pump's shaft. Like so:


Once the bolt is installed, start filling the pump down the side of the shaft with CHF11S. (red arrow) Fill it until it is almost overflowing, and then with a drill or an impact, slowly start cycling the pump. You will notice the fluid start disappearing into the pump, and bubbles emerging. Repeat this several times (5-10x) until the pump no longer takes any fluid, and bubbles have stopped coming out.

Now, remove the bolt, and install your new rotary oil seal. (22mm X 11mm X 7mm) Take care installing this seal. It has no seat, and you don't want to push it in too far:


Next, thread that cam gear back in, no need to tighten, engine rotation will do that.


Remove your vacuum, and that's it. Job done. Re-install, and hopefully, rail pressure is back. You can and should remeasure the diaphragm before installation. It should be well below 20mm.

As an additional note. I have found, that on my pump, the pressure in the pump would eventually pop out the rotary seal. I have since had a machine shop cut a groove into the pump to take a circlip, which has solved this problem.


And that's it. Hope it helps.

**some of the pics in this post are not mine, as I didn't photograph every step.

[iqraceworks]

Isn't there an electronically controller pressure regulator in the HPFP also? I thought it was pretty common for those to go bad and cause issues also?

Great post! Cool to see someone trying to repair these things...they have gotten really expensive!

[swellengear]

Originally Posted by iqraceworks

Isn't there an electronically controller pressure regulator in the HPFP also? I thought it was pretty common for those to go bad and cause issues also?

Great post! Cool to see someone trying to repair these things...they have gotten really expensive!

Thanks man. As you say, they are very pricey, so figured I'd have a go!

Re the solenoid, can't really comment. I have not had a bad one, they seem to be quite reliable. They regulate the pressure by either sending the fuel straight through to the rail, or, via the pump. It switches between these two states very quickly to regulate the pressure. (I stand to be corrected on this, but that is my observation) There are 2 o-rings on the solenoid which could cause problems I guess, but have not experienced this yet.

From having looked at a few failed pumps, my take away is that the common failure point seems to be the fluid leaking out of the pump over time. The fluid leaks into your engine oil, so there is no externally visible leak.

As above, easiest way to check, is to get a measurement of the diaphragm. This can be done with the pump in situ.

[Wolf 335]

Why do you think new seal is poping out?

[swellengear]

Originally Posted by Wolf 335

Why do you think new seal is poping out?

To be honest, I have no idea. On the first rebuilt pump, this did not happen. Perhaps down to the seal itself.

[lambo911]

I had a go at repairing my pump as oil had leaked out by the drive peg.

I followed the tips in this post and managed to get plenty of oil in through the drive, I used a mitty vacuum pump to get good suction on the diaphragm and spent a couple of hours making sure all the air was out. I then installed a new oil seal and measured the diaphragm depth which was about 14mm.

Installed it in the car and it ran brilliantly for about 15 minutes before the engine light came on with the hpfp fault which I was getting before. On startup, using my diagnostic tool I could see decent pressure on the hpfp side but after a few minutes it would drop off and the engine light came on.

I took the pump off again, which is quite quick when you know how to do it and expected to see oil again in the drive chamber but that was pretty dry. I measured the diaphragm depth and it was now 26mm.

Any ideas what might have caused this ?

[swellengear]

Originally Posted by lambo911

I had a go at repairing my pump as oil had leaked out by the drive peg.

I followed the tips in this post and managed to get plenty of oil in through the drive, I used a mitty vacuum pump to get good suction on the diaphragm and spent a couple of hours making sure all the air was out. I then installed a new oil seal and measured the diaphragm depth which was about 14mm.

Installed it in the car and it ran brilliantly for about 15 minutes before the engine light came on with the hpfp fault which I was getting before. On startup, using my diagnostic tool I could see decent pressure on the hpfp side but after a few minutes it would drop off and the engine light came on.

I took the pump off again, which is quite quick when you know how to do it and expected to see oil again in the drive chamber but that was pretty dry. I measured the diaphragm depth and it was now 26mm.

Any ideas what might have caused this ?

When I had the issue you mention above, it was because the new rotary seal was being pushed out. Was your seal still seated correctly? If not, you can get a machine shop to cut a groove to take a circlip. This solved that issue for me.

Another question, was there any fuel in your pump when you opened it?

[lambo911]

Hi,

The seal was still in place and did not look like it had moved. That's what I was expecting had happened but it was ok.

I didn't notice any fuel in the oil.

I can take it apart again to check if there is any in it now.

I used Miller MT-90 SAE 90W gearbox oil.

[lambo911]

Ok, just pulled it apart and it is full of fuel, not oil

[iqraceworks]

Honestly, with such a "mission critical" type part like the HPFP.......especially on a daily driver, I would just replace it with a new one.

Having your car broke down on the side of the road, and possibly having to get it towed....along with the time wasted, and hassle......you are probably money ahead to just get a new one from FCP

[lambo911]

iqraceworks, you are right of course but I did want to see if I could fix it.

My concern about the ones for sale is that the new BMW ones being offered do look like they are remanufactured and the copy ones seem far too cheap and I doubt they are good quality.

So I have decided to go with a second hand one from a breakers for £250 which will hopefully last for a few years.

[swellengear]

Originally Posted by lambo911

Ok, just pulled it apart and it is full of fuel, not oil

That will be the 0-rings on the bellows. These can also be replaced. I have not had to do this repair myself yet, and you will need a specialised socket to remove them.

[swellengear]

Originally Posted by iqraceworks

Honestly, with such a "mission critical" type part like the HPFP.......especially on a daily driver, I would just replace it with a new one.

Having your car broke down on the side of the road, and possibly having to get it towed....along with the time wasted, and hassle......you are probably money ahead to just get a new one from FCP

Fair enough. Personally, I much prefer to fix, than replace. (unless absolutely necessary) My rebuilt pump has been working for over a year now with no issues. Granted, it took a bit of trial and error, but got there in the end.

Each to their own I guess.

[iqraceworks]

Originally Posted by swellengear

Fair enough. Personally, I much prefer to fix, than replace. (unless absolutely necessary) My rebuilt pump has been working for over a year now with no issues. Granted, it took a bit of trial and error, but got there in the end.

Each to their own I guess.

I agree.......but when it comes to a touchy part that can leave you stranded on the side of the road, that's prone to failure anyways, I'd rather just replace it with a new OEM part.

But yes.....most of the time, I'd rather repair something or rebuild it.

[swellengear]

Originally Posted by iqraceworks

I agree.......but when it comes to a touchy part that can leave you stranded on the side of the road, that's prone to failure anyways, I'd rather just replace it with a new OEM part.

But yes.....most of the time, I'd rather repair something or rebuild it.

Yeah man, 100%. I guess I have the "luxury" of the 135 not being my daily, so if it konks out, it can just sit in my garage until I feel like sorting it.