David Borden

I have a 2010 997.2 C4S that seems slightly slow to start. I did some research and ran across several threads about it most likely being the high pressure fuel pump and at times possibly the lower pressure fuel pump.

I tested it with the Duramentric pro monitoring RPM, the high-pressure set point and the high-pressure actual value. I have started the car several times over a number of days and it takes between one and two seconds to start the car based on the data logs. Most of the time it is close to two seconds give or take. I tested this by checking the time between when the RPM registers on the log and when the high-pressure actual values registers within approx 5 bar of the set point. Once the car is running the actual values tracks the set point almost perfectly, including under full load with a set point of roughly 130 bar.

My assumption is the LPFP is fine as its able to keep up with fuel load and everything tracks great between idle and full load across the RPM range. As far as I know, the car does not have any of the codes associated with a failing HPFP.

What I am looking for is how long it should take normally to start a 997.2? Does anyone have any insight on whether this is a HPFP on its way out, or if its acting as it should?

David

Wayne Smith

One thousand one, one thousand two ... that's about the time it takes mine to start over the last 4 plus years and 85K miles. Maybe takes an extra half second in the winter.

doclouie

ADias

It could also be a sulfated battery with increasing internal resistance...

swingwing

Here's what I read on p. 42 of Porsche's 2009 Technik Introduction:

"Fuel high-pressure system in DFI flat-six engines
The fuel high-pressure system generates the injection pressure of 580 psi to 1740 psi (40 to 120 bar)."

BTW, I'd say my engine fires in about two seconds. Quick.

swingwing

I don't think you have a fuel delivery issue. LPFP's primary job is to deliver fuel to the HPFP at a constant 5 bar pressure. If HPFP fails the LPFP will supply the engine with fuel in Emergency (i.e., limp) mode. The CEL will be activated.

dspill

I was having a similar experience a year ago with my 2010 w/ ~100K miles at the time. It would turn over for what seemed a bit too long at cold start but would fire right up when hot or warm. It slowly got worse (took even longer after several days of sitting) and I had to do something. I found the same comments about HPFP vs. LPFP and was worried about replacing the HPFP only to find it wasn't that. So I took it to the dealer hoping they would be able to positively identify the problem with their PIWIS. Unfortunately the tech could not identify anything systematically but said his experience and intuition told him I needed a new HPFP. I was hoping for a more definitive diagnosis from a dealer but no luck.

Eventually I bit the bullet and replaced the HPFP (and the water pump because its in the same area) and the problem was fixed. The water pump appeared fine for what that's worth.

Good luck.

docdrs

David Borden

Thanks for all the feedback, very much appreciated! Sounds like roughly 2 seconds to start is pretty common. It makes sense as it has to build up quite a bit of pressure before it's getting the right amount of fuel.

Would it be beneficial for me to post a screen capture of the log in the thread for others to compare it to going forward?

David

jbaker136

I have the same problem on my 2009 997.2 with 55K miles. It takes about twice as long to start (crank speed is the same, very fast and strong) after sitting over night or longer then it does when sitting for only several hours or less. My HPFP was showing some external signs of pending failure (per independent, verified by dealer) but I had no other issues such loss of power or running poorly. The original HPFP had been replaced a few years ago under the campaign but dealer went ahead and replaced it again under good will warranty however this did NOT fix the long crank time problem. The dealer now thinks it is most likely the low pressure pump check valve not holding pressure over time. I notice that if I turn the key on and wait a few seconds before cranking it seems to start almost as fast as when it has not sat long so this seems to align with the low pressure pump check valve leaking pressure over time. The other possible cause could be one or more leaking injectors but the dealer says they almost never see that issue. I would love to confirm the cause before I replace any more parts.

Jeff

RGS

My 2009 C2S and My 2014 Cayman S take a while to crank and start in the colder months especially. Sounds normal to me. I did change out my HPFP on my 09 and it did not help the cranking either.