Hi there,

I have read the DIYs and many references to HPFPs since I have been a forum member, always wondering if/when it would hit me, well I think it just has and I am looking to the experienced folk on here to confirm my initial diagnosis. My CS is at ~170k klms.

For the first time in this car I have experienced hard starting, the car will crank several times before firing and then starts initially with a rough idle/miss for a second or two.

I have noted that it is worse after sitting or on cold start and if I turn the engine off and straight back on again it starts up straight away. I believe this is due to the fuel pressure bleeding off after sitting.

also experienced yesterday the 'reduced engine power' warning for the first time.

I am looking for confirmation that this is almost certainly my High Pressure Fuel Pump failing and it will need replacement. If there are any other ideas on what this could be please let me know as HPFP is an expensive part and job. I have pretty much out ruled the starter motor due to the behaviour with starting easily straight after I switch off the ignition.

Thanks in advance,

 

Hey Tim,
Yes, this sounds like it’s new pump time. A starter will not cause a reduced power warning.

 

Thanks Garrett, i ended up getting the P1026 code and some misfires on all cylinders. Is there any simple way with a scanner to confirm whether it is the HPFP even though it is highly likely? My thinking, if it were one of the low pressure pumps, this probably would not result in an implausible HPFP signal, thoughts? I am wondering how I could out rule the fuel pressure sensor before replacing the pump depending on how difficult that might be.

cheers,

 

These issues are pretty tough as I've had the components go in different ways: the regulator, the high pressure pump, and the low pump - the only thing that has not caused a failure that I've seen in this system is the filter or the pressure sensor itself. The majority of time in my cases, and other internet reports, and the fact the dealer cannot keep the pumps in stock and at times has a several month backlog, the high pressure fuel pump is the most frequent failure point. With that said, just today I replaced a HPFP on a Cayenne Turbo, and it was not the solution - but this was using a chinese eBay part... I'll be swapping the low side pump in a few days, and that will answer the question whether the "new" HPFP is a dud, or if it was actually the low side pump causing the fueling issue.

A scanner just reports the fuel rail pressure - so the high pressure - and doesn't give indication of the low side performance. If you had the time and energy and tools and don't mind working with fuel, you could hook up a gauge interrupting the low pressure circuit and measure the low pressure side output pressure while the engine is driven, to see if it dips to indicate the low side is failing to keep up feeding the HPFP. But by then, it's so easy to replace the low side pump, that at this age, I'd think it would make more sense to just replace the pump while you're there. And if you get "Fault Fuel Gage" warnings (funny how it's misspelled) - may has well replace those senders, too!

 

One more comment about low side fuel pressure measuring: unless you have some way to also measure the fuel pressure regulator activity (how much fuel blows by that's over the set point pressure) it's too hard to tell if the pump is not delivering properly, or if the regulator is bleeding pressure off too early, not letting the proper fuel pressure be maintained.

Unfortunately there is an element of "pick a part" when it comes to solving this, since each Cayenne will be different!

 

Garrett thankyou for this information. I am hoping you can help me with some more questions I have. My situation is I have an aftermarket (not CPO) warranty where if my claim is successful they will probably use the cheapest repair they can (cheap pump and minimal parts). If it wasn't covered I would do this myself with genuine parts.

1) What is your experience with aftermarket (cheap) pumps?
2) If buying genuine, the rebuilt option is ~$500 cheaper, do you see any issue with this? https://www.fcpeuro.com/products/por...he-948110316hx
3) Do I need to replace the camshaft plugs (2 parts as listed with this kit - https://www.fcpeuro.com/products/por...-948110316lxkt)
4) Are you suggesting I replace the low pressure pump while I am at it? I am at ~105K miles. Is there just one pump? - https://www.fcpeuro.com/products/por...10000074800kt1

Thanks in advance!

 

99% sure it's the HPFP, had the same issues you described, but I fixed the pump and it's working fine now: "I believe this is due to the fuel pressure bleeding off after sitting." not exactly, it's got more to do with the hydraulic oil pressure inside the pump,
"Is there any simple way with a scanner to confirm whether it is the HPFP even though it is highly likely" Yes there is, you can look for fuel pressure, at start up within 1 second you want 40 bar,
"Do I need to replace the camshaft plugs " you don't need the $80 plastic plug at all. And don't need the Engine Camshaft Plug $275 either, you can take that from your pump.

I have 3 Cayenne's, and the fuel tank pumps, none of them have failed at (116k miles, 126k miles, 156k miles), but the HPFP failed on all three of them now.

read more here, me fixing the HPFP.

https://rennlist.com/forums/cayenne-...fp-myself.html

 

I don't have any direct experience, as I've used factory parts only in the past.

Can you even get a new pump vs a rebuilt one?
I would contact the dealer and ask them about what's available - the parts supply on these has been weird in the past years - sometimes updated parts are more expensive, and leftover older parts are less, etc. In the past I've seen that some dealers can sell you pumps, while others are not allowed to unless they have to have proof of the car in the shop in order for them to order one from Porsche.

If you've never removed the HPFP before, you'll need one of these couplers: 94810511400 - the original is a brittle black plastic that will be in a hundred pieces when you remove the pump and the coupler. The newer white part is more rubbery and can survive multiple R&Rs I've seen. Now there are aftermarket versions that aren't $70: URO makes one for like $45, and Hamburg Technic has one for $35.

And unless you somehow lose it, you will not need the expensive coupler 94810511302 that is in the FCP kit.

Not necessarily; I think you just need to realize sometimes the problem can be the low side pump, and sometimes it's the pressure regulator, but most times seem to be the high pressure pump as the cause.
And on the 958, there is just one in-tank pump compared to the two in the 1st Gen Cayennes. If you truly depend on your Cayenne - as in you go off-road to places in the middle of nowhere, or you depend on the car for long distance road trips with the family, since the engine cannot run if the low pressure pump dies, it's worth considering replacing it, given its low cost: aftermarket versions are just $100, factory are $700.

 

I have decided to do this job myself. I now just need to source the pump and the plug at a competitive rate (lol). Any suggestions on suppliers welcome.

Also any tips that aren't mentioned in the DIY - things to replace while your there etc.

Cheers,

 

If you are referring to the plastic plug, You don't even need it at ...

 

Suggest staying far away from aftermarket (non Continental) pumps... The internal tolerances have been shown to be imprecise and have caused more than one Cayenne to break a camshaft due to them internally seizing.

 

I got two aftermarket pumps coming in next week. Will take them completely apart to see what the issue really is with those.

 

I have found the genuine parts in Australia, based on what I have read and the experience of others I will be purchasing a genuine reconditioned pump and the plug because they are known to disintegrate in earlier vehicles. As I understand the clutch is metal and shouldn't need replacing (and is also expensive) so I won't be purchasing that part. Planning to do the job myself when the parts arrive in the next week. Should set me back around $2600 AUD in parts after the core charge refund (which is comparable to FCP pricing without the international freight and hassle if something goes wrong). Must be the most expensive part for its size lol.

 

There's a guy on the 957 forum who can rebuild your pump.

https://rennlist.com/forums/cayenne-...fp-myself.html

 

that's me, lol
Not taking any new orders right now, got 4 pumps to do.