Loss of fuel pressure

Tiny
DENNISREISER
  • MEMBER
  • 2005 PORSCHE CAYENNE
  • 125,000 MILES
After filling up with gas engine was hard to start when it did ran bad then would die. Found codes referring to cam sensor problems, replaced cam sensor and code for cam sensor was gone, also replaced catalytic converter and now engine will start and run but for only about 30 seconds then fuel pressure would drop to 20 psi and engine would just about die then recover for a few seconds then fuel pressure would drop again, replaced both fuel pumps and seemed to be ok? After driving for about 100 miles the same problem has returned only now after driving for about 10 miles loss of fuel pressure occurs and then happens sooner and sooner, replaced with another fuel pump ran ok for awhile then died again. Somehow loosing fuel pressure? I am at a loss. Any suggestions?
Saturday, May 25th, 2013 AT 7:48 AM

5 Replies

Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
Hello,

This sounds like you have a problem with the crankshaft angle sensor which is common with theses cars. When this sensor goes out it may not set a code. This is where I would start. Here is a guide to help you see what you are in for when doing the repair. Also did you replace the fuel filter?

https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

Here is what the job will be like for your car.

Please let us know what you find.

Cheers
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Saturday, May 25th, 2013 AT 8:19 AM
Tiny
DENNISREISER
  • MEMBER
  • 3 POSTS
Have not replaced fuel filter, had a test light at fuel pump while driving and light remained on while it was failing, once the engine died test light did go off?
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Saturday, May 25th, 2013 AT 8:38 AM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
You need to do a voltage drop test for resistance in the circuit using a voltmeter.
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Saturday, May 25th, 2013 AT 9:27 AM
Tiny
DENNISREISER
  • MEMBER
  • 3 POSTS
I will do thanks! If there is a voltage drop everything is okay so I replaced the crankshaft sensor like you said and the car has never run better. Thanks for you help I love this site.
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Sunday, May 26th, 2013 AT 9:59 AM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
You can have too much resistance in any component or connector in the circuit, When a voltage drop test is done correctly you can bracket various parts or the circuit to isolate the loss point.

I'm glad you got the car fixed that what we are here for.

Use 2CarPros anytime, we are here to help. Please tell a friend.

Cheers
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Sunday, May 26th, 2013 AT 10:27 AM

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