Mark06111

So I went through the spring and summer primarily driving my Boxster GTS leaving the Cayenne to bask in the sunlight at the end of my driveway. I drove it a few times when the weather was simply annoying enough to keep the GTS garaged. Now that the weather is changing to Cayenne type 4 wheeling weather I found it time to get back into this thing, finally figure it out and fix it. Long story short, the fuel tank pumps were fine. Good pressure, good flow. The likely problem then was the HPFP. I wanted a new unit, not rebuilt but after a quick discussion with my dealers parts guys decided to go rebuilt. Warranty is the same and their experience is that they're just as good reliability wise as a new one. So finding the best price was next. Got it for about $850. Pulled the intake off and using some of the DIY's available got it pulled out fairly easily and installed without much fanfare. The first start was rough, expected as there was little fuel or pressure left in the fuel rail. Cleared all codes, restarted and now for the better part of 2 weeks it's been great. Thanks for the help and support to the team here. It's great to know folks out there are willing to help!

OK, I changed the crankshaft position sensor and the fault code related to that hasn't returned. It's been about 2 weeks. And the problem of stalling occasionally also seems fixed as it hasn't stalled since replacing that. Since then the hard starting when warm continues, however it's not once been so bad whereas power is reduced after starting. So now although it starts hard, it runs fine once started. Fault code 1023 did return however. Now I have a full tank of fuel and start further testing. I hooked up the durametric, erased the fault code and then set up to watch the fuel pump signals. Upon start, both activate. After about 5 seconds, fuel pump 2 signal drops to zero as expected. Truck continues to run and no additional faults. Pull fuse 14 (I believe this to be fuel pump 2) and it continues to run no issues. Since that pump isn't active anyway, I would expect that. I replace the fuse then pull fuse 13. Takes about 10 seconds and the truck dies. Watching the 2 fuel pump signals, it seems as it dies fuel pump 2 is activated but the truck still dies. So I leave fuse 13 out, restart. Both pumps get the signal to activate but since fuse 13 is still out it's obviously not running. The truck starts and as seems typical, the signal for pump 2 drops leaving pump 1 signal active. Again the truck dies after about 10 seconds and again pump 2 signal goes active but too late. When the motor stalls both signals are dropped. Looking at faults, now I have 1632 "Fuel pump "B" control circuit/open - No signal/communication". Also have a 0230, "Fuel pump primary circuit - No signal/communication". So I clear these. Now both fuse's in, restart. No faults. Pull fuse 14, no faults. Turn off the motor, restart and fault 0230 returns. Since fuse 13 is still in place the truck contuse to run. I put in fuse 14, then pull 13. After 10 seconds the truck dies and registers fault 2632. Code 1023 hasn't returned yet. So it seems both pumps are active on starting, then pump 2 shuts off after about 5 seconds. This appears to be normal behavior. I would have thought though that pulling fuse 13 and killing pump one that at some point pump 2 would kick in and keep the truck running. It almost seems like that's how it should and want's to work but it kicks in too late - or perhaps that 2nd pump is the problem. Any insight on this one from anyone? I suppose the next logical test would be to check the fuel pressure. I don't have the kit yet and don't know yet where to plug in either. I believe I've seen this somewhere either on this forum or on rennlist. I know deilenberger ran into a similar situation and it ended up being the check valve that's part of the in tank fuel filter. Sure seems like a potential candidate, but - would or could that contribute to a fault 1023? I'm assuming possibly yes but am not sure. From what he was saying the check valve should maintain 4 bar for 10 minutes or so. How quickly it should or could fall after that is unknown. I know that if I restart within minutes after shutting down it will typically be a hard start. Same if it's been 30 minutes to an hour. Jury is still out... Does anyone know what the failure mode is on the HPFP? What fails only when warm?

Hi Ekstroemtj. Check this DIY. https://rennlist.com/forums/porsche-cayenne-forum/944275-cayenne-s-957-v8-crankshaft-position-sensor-replacement-diy.html. Take your time, expect some bleeding but yea, it's doable. The smaller your hands the better too. The upper harness I ended up breaking otherwise it was a reasonable job. I'm still not sure if my problem is resolved yet though. Might take a few weeks before I know.

Crank Position Sensor replaced. Early indicator is good, but after reading many a story here and elsewhere that have or had similar symptoms I'll wait a while before I declare success. After replacement I took it for a 5-6 mile ride, pretty much what I would typically do from home to work or back. I turned it off, waited 5 minutes like when you refuel, then restarted. Absolute no issue, no hesitation, no roughness. Generally I would have expected a 10-12 second crank with a crappy hesitant start and some roughness. I'll be back in a couple weeks to follow up on status. If I'm back earlier than that, the problem isn't resolved. Hope to be back no earlier than January 10-15. Happy New Year! Mark

I hadn't noticed the tach issue at all but I did notice a display oddity in that the gear indicator was all mucked up. See the attached picture, lower left of the LED display. It stayed there no matter if it was in park, reverse or any forward gear no matter speed either. Nothing changed it, sport mode, not, etc. On a cold restart the problem was gone.

Update: Using my Durametric I've been getting 0335 & 1023 codes. 0335 is crank sensor and 1023 is high pressure too low. The CEL wasn't lit and hasn't been lit. After clearing the codes earlier today and starting up when warm, 0335 kicked in right away as well as the CEL. It took about 10 seconds to start and once started had no power to speak of. The 1023 didn't return yet but I'm sure it will without doing anything else. After starting I turned it off, restarted and where previously (days earlier) it started right up and acted normal, this time it started but was still crappy. I had to drive it and it was just lethargic, no throttle response, max maybe 3500 rpm and after about 4 miles showed 9 gallons per mile. I've never seen it that bad. After turning it off and getting out, seemed to be very hot from underneath with some metallic popping like the CAT's were seriously overworked. After researching the 0335 and 1023's, then checking the rail's fuel pressure set point and actuals, I'm thinking it could be the crank sensor. Driving it today was so bad that I decided to pull that trigger and picked up the Bosch unit from Pelican for just under $70 with delivery by the end of the week. I'll put it in Saturday and report back on the result. Hopefully that's it. For the $70, and with nothing else to go by it's worth a shot before going further.

Thanks!

For a while now, when warm my 08 Cayenne S cranks fine but takes a while to fire up. Cold is fine, warm is not. And recently after starting power is significantly reduced. Floor it and it takes a while to get to 4K RPM, and that's about it. I'm leaning towards the HPFP but... the last 2 days I smell an electrical sort of smell which could be the started overheating, not sure. But I can't reconcile the starter being the issue when it cranks for 10 seconds then fires and no matter what, RPM's are slow to increase to a max of 4K. HPFP? I'd naturally go there but read too that a fuel filter fixed some issues. Any codes I should be seeing? I'm not. Lost in CT - I don't want to be lost on the road when it gets below 32F !!