Fuel Rail Pressure Test with VCDS

   #1  

Jef

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Using VCDS to check/test fuel rail pressure on direct injection gas engines.


This video also shows how different control modules will do things different because that is how the Germans designed them.
 
   #2  

Jack@European_Parts

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Great video Jef.........way to go! .......... now add mechanicals to part 2 :D

NostraJackAss foreseen problem's quatrain & FACTS about Fuel systems :


When fuel PSI and Volume are in question, never omit doing actual mechanical measurements further use the OBD as a guide to compare to actual specifications obtained.

Since VCDS only sees what the controller does, this is a very important thing to factor into a diagnostic path.

OBD also can not detect vapor lock or air PSI being mistaken for fuel PSI!

"Every time" I get one of those cars no one else can fix, it was because the OBD lied to the past repair shop just like Mr. Meter did!

Keep these tips in mind and use serious safety precautions when working on the HPP system.

NostraJackAss Has Spoken!
 
   #4  

dodaman

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Hello All,

Quick question. I have been told this test cannot be done on the 3.0L A4 engine. Anyone know if this is true? Thanks.
 
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Uwe

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Quick question. I have been told this test cannot be done on the 3.0L A4 engine. Anyone know if this is true? Thanks.
"3.0 A4" engines have existing since 2002. Needless to say, they've changed a few times since then. Can you be more specific?

-Uwe-
 
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dodaman

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"3.0 A4" engines have existing since 2002. Needless to say, they've changed a few times since then. Can you be more specific?

-Uwe-
Well, I had some negative trim numbers on my 2005 3.0L. I found a vacuum leak and wanted to start looking into the fuel system. The numbers haven’t gotten worse, but they are still negative. (Just inside the +/-10%) The filter was replaced recently, and after reading about this fuel rail pressure test, I thought I’d try this. I don’t remember where I saw it, but somewhere I read this test wasn’t able to be performed on the 3.0l engine. That’s Why I was asking Uwe. Thanks.
 
   #7  

Uwe

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Well, I had some negative trim numbers on my 2005 3.0L. I found a vacuum leak and wanted to start looking into the fuel system. The numbers haven’t gotten worse, but they are still negative. (Just inside the +/-10%) The filter was replaced recently, and after reading about this fuel rail pressure test, I thought I’d try this. I don’t remember where I saw it, but somewhere I read this test wasn’t able to be performed on the 3.0l engine. That’s Why I was asking Uwe. Thanks.
A 2005 A4 3.0 still uses low-pressure MPI injection, not high pressure FSI, and I don't think it even has a fuel pressure sensor, so no, I don't think you can do this test with a scan tool. I do think there's a port someplace on it that you can connect a mechanical fuel pressure gauge to.

However, there are newer 3.0 engines that do use FSI injection on which it should be possible to run this test with a scan tool.

-Uwe-
 
   #8  

dodaman

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As always, thanks Uwe. A bit of a bummer. But I’ll look around for a valve to hook up a tester. Appreciate it.
 
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