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Rebuilding HPFP

235K views 938 replies 86 participants last post by  BA760 
#1 ·
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
 
#31 ·
yes that is the goal



I have two vendors who are interested in looking into rebuilding them. Are either of you interested in discussing this privately and perhaps, donating your pump(s) to their research to help them determine if they can rebuild them?

It is probable we can get them back and send them along to vendor #2 if vendor #1 is not able to figure out a solution.
 
#30 · (Edited)
I don't even know if this pump failed or not. I just want to know more about a piece of hardware that is ridiculously expensive. So far, I have not seen anything torn. I will dig a little deeper later on, just wanted to give you all a little something to chew on. This was a pump I picked up on Ebay a couple months ago for next to nothing and it looked like the guy was a wrecker from his other car part auctions and didn't know the value of these pumps, a perfect candidate for the bimmerfest community knowledge bank.
 
#33 · (Edited)
The 50K mile wrecked car's engine, transmission and front cross-member, radiator, condenser, fan, PS and oil coolers, and all engine bay hoses, are in my 135K 760Li now.

Purrs like a kitten. Drove it to work today.

So, does it start quicker with the 50K mile HPFPs? yes it does.

The other thing to note: car spent some time upside down when it got wrecked. I did find a cc or two of liquid gas on each HPFP hose that attaches to the nipple when I first got it. Then, after many days of testing the motor, I left it alone for more than 24 hours. While working on it to remnve the engine from the wreck, I found a good 5-8 ccs of gas on one HPFP. Maybe it's beginning to die. Maybe not.

I'll keep an eye on it and see if more gas develops there. Thinking it is "possible" that while it was upside down, something could have gone wonky and allowed some gas in there. But I know that carbon canister vent systems are meant to prevent gas leaks while upside down.

Also of note: I plan to photograph and document and make a video of, the ENTIRE gas tubing and venting and drainback system so we can understand it. BMWs TIS is a joke when it comes to this system. There are no other sources of information. Bentley does not make a manual for the E65 66.
 
#34 ·
So I went back into the pump and discovered that the piece of plastic with the "1" on the top is just a plastic seat insert for the bottom of the spring;
it pops out easy enough. Below the cap is the diaphragm. This is where things start to make sense with the posts about fuel entering the regulator
vent line. The outer diaphragm annulus appears to be constructed of a wire mesh. Sitting on top of the mesh, near the aluminum housing of the fuel pump
was a deteriorated rubber washer. The center of the diaphragm is composed of a very thin, light-green, rubber-like material that easily deforms with slight
pressure. You can see where the bore lies and where the aluminum housing is; it's that thin of a material. On the bright side, it appears the diaphragm is
sandwiched between the aluminum housing and the brass outer annulus. Once I figure out how to remove the brass annulus, a replacement diaphragm may
be able to be used provided the material and thickness are suitable for the pressure and gasoline/ethanol environment. Pics of the diaphragm later tonight on the photobucket link in the earlier part of this thread.
 
#36 ·
My HPFPs are fine for the moment, no reason to disturb them. Once the diaphragm is
identified (dimensions, material), members can source out a replacement to have on hand
should their HPFP give up the ghost in the future. The way I see it, you've got nothing to lose
replacing the diaphragm if your HPFP is identified as being bad. Picture of the diaphragm is up now.
 
#38 ·
Might be kind of awkward trying to replace the diaphragm installed but if you had access to the fuel pressure regulator face, you should have access to the diaphragm.

My guess is some contaminant in the pressurized fuel chamber impacts the diaphragm and tears it open. Once punctured, high pressure will not be achieved since it will follow the path of least resistance (vent line) and will never achieve the minimum level needed for the fuel line.

Now, what is the contaminant? I read some threads that the dealer not only replaced the HPFPs but also the fuel injectors. If they replaced the fuel injectors, something likely clogged the injectors that wasn't soluble in gas. I doubt gasoline contaminants are making it past the initial fuel filter media for all these HPFP replacements and is more likely something in the pump, maybe fine aluminum particles from a lack of lubrication?

After looking at this fuel pump, I think it's in good condition (piston travels in the bore and the diaphragm is intact). Going to do a little more research on removing the brass annulus next week.
 
#39 ·
Has anyone gotten further on the solution?

I like you have rough idle and i have replaced everything but the hPFP. Before I go after that, I would like to know if it can be repaired. IT appears that the components that break down are accessible.

Did any of the people you spoke to want to try to repair them? at 2500 that is ridiculous not to have a repair option.
 
#40 ·
Do you have gasoline in your tank vent tubing? or the tank vent valves?

I have not sent mine in for evaluation and I have tried PM-ing others to see if they are interested in doing so if needed, and have not heard back yet. I'll try to get on it next week. I am out of town all week. A few things to think about:

rare cars, probably only a few hundred 760s ordered each year.

The part is not shared by any other BMW. we might luck out if some or all of the internal parts are shared by another pump, but do not hold your breath.

The newer BMWs that DO have a rebuild option, those pumps sell in the 10s of thousands of units, if not hundreds of thousands. Makes rebuilding them much more profitable.
 
#42 ·
N73 760Li HPFP videos!

I finally had the chance to remove my 2 known-dead 135K mile HPFPs. These were gushing gas into the tank vent tubing and the tank vent valve. This was definitely causing hesitation and bad driving, due to large amounts of gas gulping into the intake plenum/manifold.

One thing I will say: I wish "I" could get $3000 labor to remove and install them. I'd earn about $1000 an hour. :tsk:

removal:

http://www.youtube.com/watch?v=wFvdOVFRp0w&feature=youtu.be

the hole in the gas vent diaphragm:

http://www.youtube.com/watch?v=qvN1iUpLEVc&list=UUN5b2Wa-qOHFD0f_axcIqyw&index=2
 
#43 ·
Good job figuring out the diaphragm was the culprit. The VW Touareg and Audi Q7 have a high pressure fuel pump that
looks very similar to the N73 pump, just smaller. Those pumps run around $200 on Ebay and I wonder if the diaphragm
can be pulled and replaced into the N73 pump; better yet, if Bosch would sell the diaphragms separately but I doubt that
will happen.
 
#44 ·
Update on the 50K mile motor and pumps in my car: at 5K miles later...

I actually pulled the quick -releases off my Tank Vent valves this morning. They were clean. If they had gas up that far in the tubing, I would be worried. I then pulled the rubber hoses off the tops of each pump (by the diaphragm that is leaking in the above movies), and there was a cc or so, of wet gas in one hose and a few drops in the other. When the diaphragms are leaking, this is where the leak starts to build up--in the rubber hoses on top of each pump. Then the gas moves up the tank vent tubing, reaches the vent valves, then gets sucked into the intake manifold. But I also suspect this is normal gasoline condensation and it rolls to the lowest point in the system and sits in those hoses on top of the pumps as well.

or, my diaphragms are leaking EXTREMELY slowly.
 
#45 ·
Fuel in HPFP vent line

It's ok to have fuel in the lines, up to 1 litre per hour per pump flows back to tank. There's a lot of info on this in their TIS manual. I'm having problems with my car misfiring, I'm changing the fuel filter/ pressure regulator to see if its the problem. When I first started to get misfires I changed all my plugs and coils only to experience worse misfires.
 
#46 ·
V12seven it depends upon which fuel lines you are talking about. There's three that go to each HPFP. supply, drainback (back to tank, even has it's own filter to clean oil and particles out before going back to the tank) and then the tank vent tubing on top of the fuel pumps which goes to the tank vent valves which feed your throttle bodies with (hopefully) just a little bit of vented gas fumes. The tank vent valves should not be sending a litre per hour to anywhere. The drainback fuel lines are what you are referring to as shepherding a litre of gas per hour. It goes back to the tank.

I made a movie that shows the routing of all this, with engine out of car, but it's buried on an SD card somewehere.

I am pretty sure changing out the fuel pump with the regulator built in, will not fix your misfire, but if the car has any miles on it, it's not a bad thing to maintain.

I had a bumpy idle on the wreck donor car I got my fresher N73 engine from. The MAFs had oil on them. Not a small amount, I mean, they were caked in visible, dirty oil. I thought I had cleaned them, but--not enough. Even still the engine ran pretty good, but seemed to misfire, especially at idle.

I swapped out the MAFS for a cleaner set and the idle cleaned right up. I know I have the "bumpy idle movie" somewhere, I'll try to look for it. but here's the After movie:

 
#47 ·
You're right, my bad. I was reading up on it late last night, hoping of course that my hpfp's are not the cause of my troubles. I plan to disconnect and plug both vent lines from pumps and connect tubing from pumps to a container to see if my engine will run better, this should tell me if fuel was making its way from the pumps to the manifold.
 
#48 ·
not a problem, understanding this system is difficult. It's complex and not obvious. to make matters worse, TIS has no theory of operation of the vent system, that I could find, and there's no good diagram of the entire system. I had to piece it together by looking at the 3.5L turbo fuel system diagrams, and add our filtered drainback to the diagram in my head.

if you are having issues with the engine hesitating and bumping due to raw fuel being dumped in via your tank vent valves filling up, remove the two quick releases in this picture (make sure you click them back on firmly) and see if you have gas dribbling out. If you do, it's getting sucked straight into the TBs and intake manifold and choking your engine on occasion.



that would be bad, mmmkay..
 
#49 · (Edited)
Well I just got done with my pump check, I didn't see you're reply but had already disconnected that yesterday and there was a little fuel there. Today I disconnected both hoses from the pump tops, plugged the hoses and connected clear tubing to pumps. On starting the engine the left bank pump quickly started filling the tube with 2 to 3cc a minute, right bank was ok. I fashioned a crude five point out of a 5mm hex key socket, it worked and was easy to use with an extension. There was some residual pressure left in system on removal of the cap and I could observe a small jet of fuel from one area at the edge of the diaphragm. The leaking pump has yellow writing on the cap as well as on most components relating to this pump, car was still under warranty when I purchased it but things are not perfect under the hood. My diaphragm looks a little messy, almost like its had sealant spread around the edge, could it be........? Could that work, short term? Not fully understanding what pressure is under the diaphragm makes me wonder, can that membrane really withstand 1700 psi or the 87 psi from the tank? I may try some petroleum resistant sealant, nothing to lose.
I've read these or forums for years, they are a great help, thanks for your input.
 

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#50 ·
I realize that the plastic cap limits the membranes movement, for this reason I hope that a coat of sealant compressed between the cap/ spring and diaphragm seat will effect a functional repair.

Mws, unrelated to pumps, I replaced my plugs with Bosch 4 prong thinking that's what was installed. All coils replaced with factory Bosch. Are the NGK laser platinum a better plug? Like I mentioned, I'm still getting misc. misfires, I'm wondering if the plugs could cause this. My car is 2003 and has 87,000 miles.
 
#51 ·
I realize that the plastic cap limits the membranes movement, for this reason I hope that a coat of sealant compressed between the cap/ spring and diaphragm seat will effect a functional repair.

Mws, unrelated to pumps, I replaced my plugs with Bosch 4 prong thinking that's what was installed. All coils replaced with factory Bosch. Are the NGK laser platinum a better plug? Like I mentioned, I'm still getting misc. misfires, I'm wondering if the plugs could cause this. My car is 2003 and has 87,000 miles.
I used the Bosch 4-prong myself. In fact the exact part number they have on realoem.com is no longer available through regular channels. I went with a vendor on Amazon that still had the old Bosch number. My engine purrs smooth as a kitten. Maybe order a Torx Plus bit set (also a new, strange 5-point design) from Amazon and remove your mafs from their tubes and use some Maf cleaner (at all parts stores these days).
 
#56 ·
HPFP diaphragm removed

After using the nitrile rubber adhesive to hopefully seal the leak in the diaphragm, I noticed that it wasn't bonding as well as I thought it would, (too gummy)' so I didn't expect much from the repair. I'm now not sure that the diaphragm is in the nitrile family, maybe it's a hybrid of some kind. I was hoping to find some thing that would bond permanently and still be elastic and be impervious to gas. After the failure, I removed the pump again and decided to remove the diaphragm, it's OUT! Or seemingly they are out, I have 2, I don't think they are supposed to be together, (like they became delaminated). I have suspicions about my car, I purchased under warranty 5 years ago but this pump and all lines associated with it are marked with yellow permanent marker. Did BMW repair this pump by laying a good diaphragm on top of the old one? If so, that means that there are diaphragms available. Can anyone confirm that there is supposed to be 2 diaphragms in the pump, one on top of the other?

I can't figure out how to upload more than 1 picture at a time, I pick 3 and it gives me the last one I picked, any help?
 

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#68 ·
Two layers

After using the nitrile rubber adhesive to hopefully seal the leak in the diaphragm, I noticed that it wasn't bonding as well as I thought it would, (too gummy)' so I didn't expect much from the repair. I'm now not sure that the diaphragm is in the nitrile family, maybe it's a hybrid of some kind. I was hoping to find some thing that would bond permanently and still be elastic and be impervious to gas. After the failure, I removed the pump again and decided to remove the diaphragm, it's OUT! Or seemingly they are out, I have 2, I don't think they are supposed to be together, (like they became delaminated). I have suspicions about my car, I purchased under warranty 5 years ago but this pump and all lines associated with it are marked with yellow permanent marker. Did BMW repair this pump by laying a good diaphragm on top of the old one? If so, that means that there are diaphragms available. Can anyone confirm that there is supposed to be 2 diaphragms in the pump, one on top of the other?

I can't figure out how to upload more than 1 picture at a time, I pick 3 and it gives me the last one I picked, any help?
I've talked with someone else to fully disassembled the pump and found the diaphragm to be two-layer as well.
 
#57 ·
Good work removing diaphragm!

How did you remove the solid annulus piece pressing the diaphragm against the housing?
Was it a screw thread and if so, what tool did you use to remove?

I have an extra pump which appears to have a good diaphragm. I could check later tonight whether its one piece or some kind of laminated part.

Any idea on what material the diaphragm is made of?
 
#75 ·
FOUND a possible replacement Bosch diaphragm!!!!



V12Seven, I need pictures of what blind puller and attachment you used to get the ring off. Also, it has to be done without damaging anything. Were you able to accomplish that?

If you are still having trouble uploading several pictures, then feel free to post as many single replies as is needed. This is really important.

I bought, from England (they are not available in the US)

A 2002-era VW/Audi diesel direct injection pump, # 06D127026J that a rebuilder told me shares the same exact bosch diaphragm part number!!! They are cheap enough that if only the diaphragm were damaged on ours, then our pumps can be repaired for hundreds of dollars buy buying these new and removing the diaphragms!!!

 
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