Cayenne S 2007-2010 (957) High Pressure Fuel Pump (HPFP) Replacement DIY - Page 3 - Dorkiphus.net
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  #21  
Old 10-18-2015, 08:42 PM
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Quote:
Originally Posted by cmartin View Post
I picked 2008 see pumps listed as right and left, is it high and low pressure? Just curious.
No, those are the in-tank pumps. They are part of the low pressure system and they are significantly cheaper than the HPFP. The HPFP is on the driver's side cylinder head, right up against the firewall.
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  #22  
Old 10-19-2015, 12:24 AM
PorscheTX928 PorscheTX928 is offline
 
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Default Low Pressure Fuel Pumps

Yes, the low pressure fuel pumps are mounted inside the gas tank on the left and right side right under passenger seats. You have to open up both to do anything with either pump since they have inter-connecting fuel lines. The FPR is mounted on the opening above Right fuel pump, and the fuel filter on top of the left pump. I will tell you that the fuel filter and FPR should probably be replaced if you mess with pumps. I have seen many instances where pumps were replaced only to have similar issues which turned out to be the filter or FPR. My Filter was filthy, at 85K miles. I have replaced everything - Fuel Filter, FPR, and L and R pumps. MY 2008 CS is running better, but now I am getting something similar to the OP...So, I thought I would ask about the HPFP. I posted this in another forum, but the forum seems to be dead, no one responding.

Repost:
I have had a fuel delivery problem with my 2008 CS now for a few months. I have replaced the FPR, filter, and two fuel pumps...but am still having issues with a long crank time and pretty crappy running over 2K RPMs. Sometimes, usually when car is cold, the car will run perfectly, but once it heats up, it begins to act up.
I have a car scanner that can read some of the Porsche values so I decided to check on the high pressure at start up, and after running for awhile.

Ok...so after car warms up, the fuel pressure set point goes to 0.00...actual stays constant at around 5K mbar....at this point, you can give it gas and the actual value might go up to 6500 mb, but thats it....set point does not change.

I turned off the car and back on...I get a fuel set point of 40,000 mbar...actual around 32,000 mbar....car seems to run pretty good right after a restart...I gave it some gas, and the fuel set point went to 51000 mbar and the actual kept pace at 49800 mbar. BUT, after a few minutes the setpoint drops to 0.00 and stays there, and the actual again stays at 6500 despite giving it some gas. trying to bump it up.....

So what does all this mean? Seems like my HPFP is dying out after the car warms up...although even at start up it does seem to be running that well as it takes awhile for the car to start. Could it be a bad relay? Which relay is for the HPFP? Perhaps I can swap it out with another similar relay to test. Is there something else that would trigger the HPFP to turn off? Thanks in advance for any help.

__________


Also, if anyone has any questions regarding the low pressure pumps...I would be glad to help. Main things when working on them is (Do them on empty fuel tank!!!! Otherwise, you will be dunking your hands...have 1/4 tank or less and its not too bad, Depressurize fuel lines before disconnecting battery, work slowly and keep track of lines[sucks to forget a connection].)
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  #23  
Old 10-20-2015, 12:16 PM
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I had the same issue with the high pressure set point disappearing after a while, even with the Durametric tool. I don't think that it actually is a problem with the car, but rather a connection problem through the OBD2. The reason I say that is that I saw the set point drop out quickly sometimes and much later into a drive cycle other times, but the problems still existed even with the set point there. Replacing the pump fixed the car's performance issues, but did not fix the set point dropping out issue.

With a healthy HPFP, the actual value should track the set point almost perfectly. I had the same symptoms - the car ran better with a cold HPFP and worse once the engine/HPFP warmed up.
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  #24  
Old 11-15-2015, 03:12 AM
PorscheTX928 PorscheTX928 is offline
 
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Cool

Im pretty sure the HPFP is my issue. I do have a question about your DIY project. Is it possible for the problem with my pump to just be the cam stopper? You said that you didnt notice it when you removed your old pump because it has fallen apart. Is it possible that the stopper was the original cause of the pump not working? I am guessing the cam turning helps build pressure in the pump? I was going to take off my pump today to check, but it rained all day. It would be great if all I needed to replace was a 70.00 stopper.
I have an 08 Cayenne S, and the cheapest I have found the pump has been 936.00...I just put 1200 putting in the low pressure pumps, FPR and filter, I hate to spend another 1K on this car....especially since my funds have also been going to a project 928 im working on.

If its doable, i may take the pump out and leave it out until i get the new pump. And, if its the cam stopper, I can replace that and see if that is the issue.
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  #25  
Old 11-15-2015, 07:05 PM
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Unfortunately, no.

The cam stopper is only useful when assembling the components. It holds the HPFP clutch in place on the end of the camshaft. When I first assembled everything I didn't notice that the clutch had fallen out completely since the stopper wasn't there to hold it in place. I ran the car with the new HPFP and had the same symptoms as before. After removing everything again, I noticed that the clutch was missing and fished it out of the undertrays. Then I got a new stopper to hold the clutch in place while I installed the new pump again. With the new HPFP now engaged on the camshaft all issues were fixed.

As a side note, the HPFP "clutch" is just an aluminum piece that serves as an adaptor between the end of the camshaft and the nose of the HPFP. You are correct in that the HPFP is driven by the camshaft.
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  #26  
Old 11-27-2015, 04:25 PM
PorscheTX928 PorscheTX928 is offline
 
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Cool able to locate a cheap used HPFP

I am excited. I was able to locate a used HPFP for 199 Euros. Around 210 USD. I figure if it only lasts a year, it will be worth it. I just through almost 1500 into the rest of the fuel system so if I get a year off the used pump or at least 6 months, it will give me a little time to recoup from this hit to my wallet. At 200.00, it was a chance im willing to take.

I ordered stopper just in case from a supplier for 41.00 along with a gasket that is not mentioned in this post. Not sure if it is needed, but it was only 2.96 so I figured to replace just in case.

I will update once I get part and install....this has been a long road for me...and I would be happy to get fuel and performance issues out of the way once and for all. I have had start and performance issues for close to 6 months now, so if this is the last step, I would be a very happy p!g owner. Current symptoms are erratic idle, long starts, and complete power loss if you accelerate rapidly. I can get up to 60-70 with no problem as long as it is a slow, steady acceleration. Because of this, I havent driven it much on my hour and a half commute because I dont trust it. Oh, I also get the P1026 code, and have the lack of pressure as mentioned in my previous posts.
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  #27  
Old 12-01-2015, 04:25 PM
lubridges lubridges is offline
 
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Default Hpfp 2008 pc s

This was a very good read. Curious if your check engine light activated at any time during the degradation of performance with the pump?

My mech has indicated that my pump may need replacement and the cost are ~$1200.00 (very pricey)

Regards,

Lucien
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  #28  
Old 12-02-2015, 12:36 AM
PorscheTX928 PorscheTX928 is offline
 
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lubridges - Yes, ck engine light will trigger codes, especially 1024, it seems. But you will get codes for just about everything because it is making everything else run crappy. So I got misfire codes as well. Well, 1200 sounds just a little high...most say other than being hard to get to, this is a pretty simple job. As mentioned, one person had pump out in 30 min. I have seen the pumps as low as around 800.00. So if you choose to put it in yourself, you can save a little money. Make sure you get the newest part # if u are buying new. There have been several upgrades and versions of the HPFP, so make sure you are not buying an old version. For my 2008 Cayenne S (no turbo) it is 948-110-315-07
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  #29  
Old 12-03-2015, 12:23 AM
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I also got codes while the pump was failing. Also experienced misfires and all kinds of other codes per above.
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  #30  
Old 12-05-2015, 07:35 PM
PorscheTX928 PorscheTX928 is offline
 
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Ok....I received the stopper yesterday, so I was able to do the HPFP switch out today....it took me about 4 hours total...but to get the pump out it was pretty quick....30-40 min...I had some issues with the piece between the pump and the cam- it fell off when i pulled the pump out and I had to crawl under the car and search for it....it was stuck in a spot that was very hard to get to. Also, once the new pump was on, I had a bad fuel leak that took about an hour to fix...it was the small hose on top that is not very flexible. I bent it a little so it fit better and it solved the problem. I took the engine hoist eye completely off because it was in the way. I also removed a few other things to make room...I have huge (Fat) hands....with little hands, it would have been a snap.

Also, no one has mentioned, but there is a gasket on the pump that needs to be replaced. I order it and it cost around 3.00...the gasket on the old pump was bad. The stopper was worn down also so I am glad i purchased it. My cayenne now runs better than it did when i purchased it. I am taking my gf out tonight!!!! Woo hoo...unfortunately, I still have to go back in and put the plate back on, and the engine hoist mount, and the vanity engine covers....but Ill leave that until my hands heal a bit....you will get them scratched up squeezing them through very narrow openings.
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