2003 Cayenne fuel system

[Cap'n John]

Lots of questions:
1. How many fuel pumps does this car have? Obviously there is a driver side (DS) and passenger side (PS) pump in the fuel tank, is there also an additional pump up front under the hood?
2. Which of the two pumps in the tank are considered the "main" pump? Which is considered the "high pressure pump"? Is that the same thing?
3. Are the "sucker pumps" on both sides an integral part of the fuel pumps, or are they separate items?
4. This car runs very rough with less than 1/4 tank showing on the fuel guage. This seems to be a common problem. Which of these items is responsible for that? Doesn't seem to make sense to replace everything.
5. What exactly is a fuel system delivery test? Is this something that is performed with a code analyser or does it require an additional tester?

Thanks for any help or suggestions!

John Saggese
john@saggese.net
6/22/20

[guru944]

Cap'n John;

Yes, there are two pumps left side -primary and right side -supplementary.
They are staged, such that primary works to supply fuel while engine is running and secondary right pump comes in under heavy load, throttle activation , acceleration and above ~ +40 mph. Fuel system is returnless and ECU controls via PCM signal.
Due to some oem defect issues, you may have a cracked fuel pressure regulator housing or a defective fuel pressure regulator (right tank cover); Typically you will smell fuel especially when tank is full or under heavy throttle and also have a emissions leak in tank. Code P0455. Also you may need to change your fuel filter, (left tank cover) every 3- 5 yrs.
You may also have some dirty/clogged fuel injectors a good fuel injector cleaner will resolve that in 2 applications with 93 octane
Its a big job to service fuel system and can get pretty expensive. Personally I would service everything including replacing both in tank fuel pumps. I did this job last year and had a noticeable improvement in drive-ability and power. Parts cost was under $650.00. See Pelican Cayenne 955 troubleshooting/ fix section.