08 Cayenne S - Cranks when warm, long time to start

[Mark06111]

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 !!

[JFP in PA]

You need to have your fuel pressure and delivery checked, which requires some special equipment due to the high pressures involved.  A failing fuel system does not always result in codes.

[lewisweller]

On 06/12/2017 at 6:18 AM, Mark06111 said:

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 !!

Classic hpfp symptoms, software will show the pressures which identify the specified and actual, this will tell the story more accurately. 

Fuel filter can be blocked but less likely. 

Low pressure fuel pressure regulator and low pressure fuel pump (left primary) can also cause long cranking and struggling to rev up. 

Don't waste money on parts until you confirm the fault. 

[Mark06111]

Quote

Appreciate the input and indeed nothing will be bought until i've had the chance to isolate this better.  So far the HPFP puts out 40bar after starting, right at the set point.  After turning it off, it drops quickly to about 5bar.  I haven't been able to go further than that yet.  Today after starting cold, driving a bit, stopping for 30 minutes, then restarting it started fairly and didn't have the huge power loss it does typically but the pig stalled out approaching a stop sign.  The restart was then the typical 10-12 seconds as when warm with the huge power loss.  I've hit some spotty information on how to test various things.  Is there one or two high information threads or articles that explain the tests and what the results should be?   I'm still looking (when time permits - soon this might be lots of time if the pig dies altogether :-))

Thanks!

 

[Mark06111]

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. 

 

 

[lewisweller]

16 hours ago, Mark06111 said:

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. 

 

 

I think the crank code is triggered as a result of the bad running. 

My bet is the hpfp is the real issue here. It's expensive I know, so understand your hoping its the crank sensor at 70 bucks instead. I hope I'm wrong and your right for your wallets sake. 

Good luck. 

[JFP in PA]

21 minutes ago, lewisweller said:

I think the crank code is triggered as a result of the bad running. 

My bet is the hpfp is the real issue here. It's expensive I know, so understand your hoping its the crank sensor at 70 bucks instead. I hope I'm wrong and your right for your wallets sake. 

Good luck. 

 

Perhaps not.  Porsche has a long history of using the crank sensor to tell the DME that the engine is turning over and it is OK to run the fuel pumps.  No signal, or a very intermittent CPS signal and the DME thinks the engine is not turning over and shuts off the fuel pumps.  Two usual giveaway signals: Hard starting when warm, and the tachometer does not move when cranking the engine over.

[Mark06111]

On ‎12‎/‎20‎/‎2017 at 2:20 PM, JFP in PA said:

Two usual giveaway signals: Hard starting when warm, and the tachometer does not move when cranking the engine over.

 

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.

 

Edited December 23, 2017 by Mark06111

[Mark06111]

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

[ekstroemtj]

Hi Mark

 

since 2 weeks I experience the same issue. Cranking several times before firing. Never had it before. Strange running car almost only when it was filled up. I got a code. P0335. Crankshaft Sensor. I could delete the code but the problem cAme back after some days. First i was thinking it is related to my faulty AGR Ventil. But I am shure it’s the sensor from crankshaft to dme. Bought the Bosch part.

 

could you do the repair by yourself? What read at Pelican it’s hard to connect in the engine bay close to firewall. May i ask how you did it? Thank you

Edited December 28, 2017 by ekstroemtj

[Mark06111]

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. 

[lewisweller]

On 30/12/2017 at 5:11 AM, Mark06111 said:

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. 

Thomas ours is easier to do as there is no hpfp or harness in the way of the sensor plug harness on the 03-06 ctt. The locations are the same as the diy posted and it helps to have a friend in my case the wife work from the top and you work from underneath, disconnect from top and bottom and pull old one out from bottom. Fit new sensor by dropping it from the top down with you waiting at the bottom to grab it and fit. Piece of cake really compared to other nightmare repairs ie alternator....... 

[ekstroemtj]

@Mark06111 & @Lewis

 

thank you very much guys. Have found the harness connection behind the air pump. Should be easy to access. It needs a lift I guess to reach the sensor in the bell housing. 

 

HAPPY NEW YEAR FOR EVERYBODY!!!

[lewisweller]

On 01/01/2018 at 6:17 AM, ekstroemtj said:

@Mark06111 & @Lewis

 

thank you very much guys. Have found the harness connection behind the air pump. Should be easy to access. It needs a lift I guess to reach the sensor in the bell housing. 

 

HAPPY NEW YEAR FOR EVERYBODY!!!

Set suspension to max height and switch off regulation and there is enough room to go under just, but to be comfortable jack it up a bit as well and use jack stand for safety.

Happy new year  

[ekstroemtj]

@Lewis thank you Lewis.

 

my mechanic did it for 50 EUR

i didn’t have time

[Mark06111]

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? 

 

[lewisweller]

On 21/01/2018 at 7:42 PM, Mark06111 said:

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? 

 

https://rennlist.com/forums/porsche-cayenne-forum/986829-2008-cs-with-p1023-error-code.html

 

This sounds like the same issue. Check valve built inside. Whole hpfp needs to be changed. Watch out for the cheap ones, infact even Porsche had some go bad after only a few 1,000 km. 

Some guys are on there 2nd or 3rd hpfp for similar symptons. Expense item so make sure it's that before you shell out. 

[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!