deilenberger

My mis-type. They said it was in the filter. Both pumps go to the filter, then a single line goes across to the FPR, and a single line from the FPR to the fuel rail. There is the "excess" line from the FPR (where the "extra" fuel goes) that goes back and dumps into the pumps (I assume to keep them flooded even if the truck is at an extreme angle.)

If you study the plumbing diagram, it makes sense that the check valve be in the fuel filter - it's the place the flow from both pumps is combined.

I suspect the check valves in the pumps are primarily there for two reasons (1) to keep the pumps filled when they're off if the fuel level is below the pump (2) to keep one pump from pumping into the other one, since the outputs are combined where they go into the fuel filter:



You can see the two fittings on the bottom where the pumps attach, and the single output pipe (with the black end) that goes over to the fuel-pressure-regulator. It would seem fairly easy to have a check valve over the output pipe that closes when flow stops.

Interesting that it screws together - love to get a bad one and take it apart and see what is in it..

I thought more about the function of the FPR in the circuit - and it woudn't make too much sense to have a check valve there - since the high-pressure side of the FPR has both the input from the fuel filter, and the output to the fuel rail - plus the actual regulating valve output. You'd need a check valve on output to the fuel rail, but that would eliminate the over-pressure relief function of the FPR when the engine is off (apparently dead-headed FI rails need this - there are a number of "interesting" stories on the Interwebz of people who added an in-line check valve to their dead-head FI system, on the line going to the rail, and shortly after found things like injectors popping out of the rail. There is apparently some hammer effect when the check valve closes. Having the FPR regulation-valve open to the line/rail avoids this - the FPR dumps the excess pressure buildup..) But I digress..

They said it was in the fuel filter, since that's what made it start behaving I have no reason to doubt them.

sup44

Hi Deilenberger,

Are you still around? I have a 2009 Cayenne S that sounds like it is having similar problem. Im hoping I can post a video of what it sounds like when I tries to start up and you can tell me if it is the same problem you encountered. Pls LMK.
Thanks,
Mark

deilenberger

Hi Mark,

Sure - I'm still here someplace.. let me know when you post the video..

sup44

Just went out to take video.. figures... started up 3x without showing the problem.. I went and changed the battery yesterday thinking its was a weak start due to that, but that didnt fix it. not sure if it is the same problem as yours. Mine sounds like a weak battery trying to turn it over.. turns over maybe 2x then stops. then I can turn it over again and even though weak, it starts..

now it is raining.. once it stops i'll see if I can reproduce the problem and take that video..thanks,..

deilenberger

Sup44 - was the battery you installed fully charged? Typically - even with "dry-charged" batteries it's recommended to charge them overnight before installing them in the vehicle.

It doesn't sound as if your problem is the same as mine was..

With mine - it turned over fine - but it took a while for the engine to actually fire, and when it did it fired poorly and ran slow. Since the Cayenne has the auto-starter function (where the starter keeps turning once initiated until a certain engine RPM is reached) this meant the starter motor was still engaged after the engine started. This caused an unDogly screech as the engine overrode the pinion gear on the starter..

If I shut it off when it did this - it would always start fine on the 2nd try since there was now residual fuel pressure in the fuel rails.

Yours sounds like either (1) bad battery - or not fully charged battery or (2) bad connection between the battery and the starter or (3) bad starter. Or a combination of two of these.

sup44

Thanks for the info deilenberger. I havnt been able to replicate the problem. So maybe you are right and the battery just needed full charge before I installed it... so far so good...

markar

I think this will be your starter motor? I have same problem when car is been running for couple hour then it wont start again until its cool down. Starters are sensitive to heat.

Slow Guy

If the starter is sensitive to heat then they sure put them in a ****-poor location. The starter is located on TOP of the engine block between the 2 heads and under the intake manifold, not too conducive to keeping it cool.

markar

Yes you right about that, i just buy my 2008 Cayenne S with bad starter from Porsche dealer
Hoping they will fix it free

LABoomBoom

Deilenberger,
Seems like you're the go to guy on this one. I have a 2006 S Titanium w 62k.
Went away on vacation and my Dad bought a bottle of Chevron Techron Concentrate Fuel System Cleaner and filled her up. Ever since that when I fill the tank it takes three tries to get her started. First two tries all you hear is clicking for 3-5 seconds. Third try always starts up with a low rumble and low rpms. This only happens right after I fuel up. Every start after is fine on first try till next time I refuel. I've tried refueling on half tank, quarter tank and almost empty and all three produce same result.
Any idea what it could be or where I should start? Hopefully not an expensive fix with the holidays around the corner.
Oh an I replaced the coils and plugs last year.

deilenberger

LaBoomBoom,

Sounds like a starter problem, although the clicking could indicate a battery going bad. I'd have a load test done on the battery under the drivers seat to see it's condition. If it's OK - then the starter relay might be worth checking (under the panel under the cowl in the fuse box IIRC..) and if all those pass muster - it's probably a starter. And that might get expensive unless you can find a place to rebuild it. Getting to it isn't too awful a job, but it does require R&R of the intake manifold (you can find details on that job by looking for write-ups on replacing the cooling pipes.) And if you're going in that far - then you may want to consider having the coolant pipes replaced if they haven't been done. Eventually they will fail.

Oh - one other thing to check. The ground cable to the front battery (your S probably only has the front one) - connects to the chassis with a big-*** (tech-term) bolt that is under the carpeting right in front of the seat. The bottom front of the seat pulls out (the carpeted part), then you can pull the carpeting forward a bit and see it. These have been known to loosen up and cause these sort of symptoms. Fix would be to remove it, clean all the contact surfaces until they're nice and shiny and reinstall it. That's a no-cost fix for even beginning DIYers. Since you've done coils/plugs - this should be quite simple for you.

bigbuzuki

Wouldn't go changing the starter just yet.

You have a fuel tank vent valve or fuel tank cap issue.

https://rennlist.com/forums/porsche-...h-already.html

deilenberger

How would that cause "First two tries all you hear is clicking for 3-5 seconds"??

It might cause a non-start condition, but AFAIK it's not going to cause a non-cranking condition. Perhaps LaBoomBoom can clarify what he hears exactly.

CALMOTION

My car 2005 CTT started doing Click on the first try sporadically and start on the second try. Was wondering if this is battery. Thanks in advance

cordsig79

Go by Autozone or Batteries Plus, ask them to measure CCA, cold cranking amps. If you are below 700 CCA, its dying or dead.

This is an hour long DIY, you can probably get a coupon for 15% off online for Batteries Plus, and buy the 12 spline bit to remove the seat and rock it back @ autozone.