Hi Guys
I have a 2004 turbo with a starting issue. Occasionally, the car will not start immediately when cold and has been left for a few days. It takes a little gas from the accelerator to get it to fire, then it starts and runs fine for the rest of the day. No dash warnings.
I remember this happening on a 1977 Carerra 3.0 and I replaced the fuel accumulator which wasn't holding fuel pressure overnight and causing similar starting issues.
Does the Cayenne have some similar device to store fuel pressure overnight?

many thanks

Robert

 

There is no fuel accumulator on these cars or any other Motronic fuel injected cars that I am aware of. Mechanical fuel injection systems, like the CIS system on your 1977 Carrera 3.0, required fuel accumulators due to the nature of the mechanical fuel injection which opened all injectors at the same time. The fuel accumulator helped to serve this sudden fuel demand and maintain a more constant pressure in the fuel system. A bleed off in those systems resulted in starting problems for a few reasons: 1) these cars did not have fuel priming systems, 2) until the accumulator itself was repressurized there would be insufficient pressure to open the mechanical fuel injectors.

When you open the driver's door prior to a cold start do you hear the fuel pump priming? This should be audible for a second or two. The intent of this, of course, is to pressurize the fuel system so that when you go to crank the car the fuel system is ready to do its thing.

Do you have access to a scan tool? I know that you said that there were no dash warnings but there may still be codes stored that would provide clues. How does the car run otherwise? Does it idle well and deliver smooth power? Have you stayed on top of regular maintenance items (plugs, vacuum system, etc.)?

 

Hi Brett
Thanks for the reply. I do hear the fuel pump working when the driver's door is open and the car runs very well.
I do have a good scan tool but I haven't got any codes stored. I can read real-time data if needed.

I have had this issue only 2-3 times. I have been wondering if these were times after I had been working on the car with the driver's door open for extended periods. Could the car be flooding with fuel when I next start it? I haven't considered this before. If it happens again I will try to run round the back of the car to see if it smells of unburnt fuel.

Could this be an option? Would the symptoms be the same?

 

Strange. I doubt it's a flooding issue as the fuel injectors are only going to open when commanded by the DME and a leaking fuel injector is more likely to cause problems on a warm start then a cold start.

It almost sounds like an issue with the canister purge valve. When this goes on the fritz it will throw a code for sure but yours may be in the early stages of failure.

Since the issue is so sporadic and infrequent you may just have to wait until it becomes more regular in order to diagnose it properly.

 

The driver's door pining only works once every 10 or 15 minutes. It won't do it for repeated door openings, like you won't hear it the 2ns time you open the door of you do it right after the first time. There is also no way for it to flood the engine as the injectors shouldn't open during this process (a leaking injector being the exception). .