My HPFP in Bank 1 needs to be replaced, I ordered the part and bmwoem1 is going to be replacing it.
The car never stalled, only thing I notice is a long crank in the morning, other than that the car runs fine.
I was thinking to sell the faulty HPFP on eBay (of course disclosing that it floods the fuel tank vent valves), but then thought if there is someone that rebuilds these, I would rather have it rebuilt and replace the HPFP in Bank 2 with the rebuilt one. Any thoughts? Thanks
"Pressure attenuator
The excess fuel delivered by the high-pressure pump is returned through the fuel-quantity control valve into the pump feed area. The pulsations generated in the pump in the process are absorbed by the spring of the pressure attenuator (12).
The pressure attenuator is separated by a diaphragm (11) from the pump feed area."
So, does that mean the diaphragm actually does see 120 bar pressure, or is it only feed pressure?
The diaphragm should only see feed pressure unless you have a problem with valve #2 (which could be a reason the diaphragm rips) Although the fuel filter has a pressure regulator that should override that fear.
This activity on this thread is great. Also, I have a feeling we are all going to be in for a first or second round of HPFP failure soon, so this thread will likely get even more action.
I'd say we need answers to this:
1] are all the vendors we have identified unable to source the original diaphragm from Bosch? I need help from you all to look up possible HPFP modifiers or vendors, use the pictures and part numbers and ask them if they have a good enough relationship with Bosch that they can get that part.
2] is the diaphragm gas permeable? why does it vent? It would be great to know this.
3] can our European brothers and sisters please assist us in finding a good and inexpensive source for a brand new VW or Audi pump with this diaphragm ? I think I saw something for around $400 US each, but can't find it again.
4] if we cannot get any good responses for this, then we might want to approach Raj at Beisan Systems. I have already talked to him about this before, but since he's not a fuel pump expert, I decided to try Performance Diesel first. He got us the interchange parts, that's half the battle. But he's not confident he can make a good diaphragm, even though he has material he thinks is suitable.
Yeowch! $600 US each to get it shipped. Thanks Irish, that puts it into perspective. The only good thing about that is of the other spare parts on it can be used as well. I pinged the seller and asked he knew of any other cars/applications a similar pump would fit, that might be cheaper when new.
Pressure damping vent valve: N73, N73TU Installation location
The pressure damping vent valve is located on the high-pressure pump (cylinder bank 7-12) on the front of the engine.
Construction
Item Description Item Description
1 Vent line to fuel tank ventilation (scavenging air line)
2 Pressure damping vent valve
3 Cylinder bank 7-12
4 Vent line
5 High-pressure pumps
6 Feed line
7 High-pressure pipe
8 Fuel return line
9 Fuel tank
10 Return cut-off valve
How it works
The pressure damping vent valve is fed with vehicle voltage via terminal 87 and is actuated by the earth section of the DME. (the pressure damping vent valve and return cut-off valve are actuated together and simultaneously)
-
When the electric fuel pump is running, the pressure damping vent valve is switched so that fuel will flow into the fuel return line and not into the scavenging air line in the event of a defective pressure damper.
-
When the electric fuel pump is not running, the pressure damping vent valve allows pressure between the vent line for the pressure dampers and the activated charcoal filter to be equalised (via the scavenging air line).
SBT Pressure damping vent valve: N73, N73TU BMW AG - TIS 16.11.2013 07:13 Issue status (12/2007) Valid only until next DVD is issued
How it works
The return cut-off valve is fed with vehicle voltage via terminal 87 and is actuated by the earth section of the DME.
(the return cut-off valve and pressure damping vent valve are actuated together and simultaneously.)
While the engine is running, it allows leaked fuel to flow back to the fuel tank. Shortly after the engine has been
started, current is applied to the return cut-off valve to prevent a drop in pressure in the feed chamber of the highpressure
pump. A drop in pressure in the high-pressure pump would result in steam bubbles forming
>current is applied to the return cut-off valve to prevent a drop in pressure in the feed chamber of the highpressure
pump. A drop in pressure in the high-pressure pump would result in steam bubbles forming
>
so, if cavitation happens, I am thinking it must be that the diaphragm is gas-permeable to vent the "steam bubbles" which form in the feed/supply side (on rare occasions). If "steam bubbles" left in the pump, they could make it run like crap I would imagine. Last thing you want is a foamy HPFP.
any one else think otherwise?
The reason I am trying to nail this "gas-permable-or-not" down is:
1] it would not be smart to simply cap off the vent, even if one wanted to try it.
2] steel diaphragms appear to be out of the question.
A fault with the return cut off valve or it`s control function can cause the scavenging line to fill with fuel , this has been found on a couple of V12`s . It could also be the reason for the diaphragm failure .
Don`t know where the audi line goes .
Just out of curiosity - Do the tears in the diaphragm(s) coincide with the edges of (#12) Pressure attenuator plate below the spring? Are the edges of the plate rolled (cupped)?
My opinion is that the diaphragm(s) are not designed to be permeable from what I've read. I think the two layers are probably designed for flexibility & strength.
I called that guy and he said he tried a bunch of solutions and they all failed. He personally drives a 760Li, which is why he attempted it. I never asked him exactly what it was he tried. Does anyone have the time to call him and find out? If you get him on the phone, the more specific you can get him to be, the better. It would be good to ensure we are not heading down the same path.
I'd love a $50 solution to the diaphragms, but if I have to pay $600 each, to get them shipped from England, I just might.
MWS wrote.."I'd love a $50 solution to the diaphragms, but if I have to pay $600 each, to get them shipped from England, I just might."
My wife ordered $30 dollars of hair product from Amazon. Free shipping, not an amazon prime vendor.. My surprise came the next week when a package came in the mail from London. Weighed about 1 1/2 lbs... Thus someone in Europe knows how to get items here cheap. Just my 2 cents worth..
>Why not just pull the guts out of the existing fuel attenuator and put an external one on the outlet hose?
Just saw this. a bold move, to be sure. Using some other damper might have a tension that's not compatible for the pulsations coming in. If we get a replacement diaphragm in the stock pump, and if other components are not failing internally, then the diaphragm replacement "might" be able to be done on-car, and with little effort. The covers on them are easy to reach. The stupid tamper-proof bolts easily removed with a vice grip and then replaced with something good from McMaster Carr. That would make the experimentation and install of an external damper just as much, if not more work.
I think you're on the right track, though. buying inexpensive pulsation dampers and dissecting them to look for a compatible part, could come up with an interesting solution.
You know, I almost wonder if you couldn't just patch up your old membrane with
some thin fiber mesh and new viton sheet and ethyl acetate, or other similar Viton
solvent; I mean the membrane is so thin.
Yup, I figured. Different membrane thickness, so, different retainer ring thickness, so; CNC machine in Czech Republic. . OK folks. We have to find a replacement diaphragm. And, it needs to be the same thickness. Best thing we can do is figure out how to get them from Bosch.
Again, we are all set if one wants to buy a couple new pumps from England. It's just $1200 or so, including shipping. That is why we need a less expensive source for the pumps. According to the parts list Performance Diesel had, that list I gave are the ONLY pumps that have that exact diaphragm. We might find various pumps and pulsation dampers with diaphragms the same size, but being able to clamp and retain the diaphragm requires precision, and Nandro has done his homework.
Nandro, will you sell a kit of the retainer ring and membrane?
There I have different membranes, which must then be adapted to the spacer ring.
These kits, ring + membrane must deploy certain procedure and therefore it only makes himself and selling it to ensure proper function.
Ok guys - it's obvious that he's not going to sell just the diaphragms. He's in it for the American dollar, not to help fellow BMW owners. His english appears to be getting better, he made a halfway decent video, but it looks like they need light bulbs (poor lighting). You're nuts if you send your pumps (money) to Ostrava (where ever the heck that is). You're on the right track, just get some diaphragm material and give it a shot. (That's what he did)
hi guys... did anyone tried prying on some toyota, gmc and ford fuel pump? i think it operate the same way our pump did and it mey yield a diaphragm that my fit.
hi guys... did anyone tried prying on some toyota, gmc and ford fuel pump? i think it operate the same way our pump did and it mey yield a diaphragm that my fit.
Yep, I opened up a newer HPFP from a GM vehicle, and most of the newer designs use a metal layered diaphragm with the vent sealed
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