Fuel pump doesn't prime when I open the door - Club Touareg Forums
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post #1 of 14 Old 10-17-2015 Thread Starter
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Question Fuel pump doesn't prime when I open the door

I'm hoping someone can lead me to the right direction. I had the 30 sec shut off after startup. So i replaced both fuel pumps and the fuel filter (which was very dirty) and everything is back together. I open the driver door and I don't hear the pump priming at all. Engine turns over fine but wont start, and I stop it after a few seconds (I dont want to burn out my starter).

I pulled both 404 relays and try get same results.
I checked both 15Amp fuses both are good.

My battery is weak from me trying so much so I have to charge that now.(Its at about 11.8 Volts now.

My question is what else tells the pump to prime when you open the door?

I checked all the hoses are hooked up correctly, They seem to work only one way. Does the polarity mater on the green wire connector on the filter assembly?

Any help is greatly appreciated. Thanks in advance.
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post #2 of 14 Old 10-17-2015 Thread Starter
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Fuel filter

Fuel filter before and after


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post #3 of 14 Old 10-17-2015
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It sounds like only one of the fuel pumps is working. I am pretty sure that the 30 second cut off was a sign that only one of the two fuel pumps was pumping fuel. Seach the old threads as I am pretty sure that it was explained in one of them.

VW put out some PDF's that explained the theory behind the touareg systems. I am pretty sure that one of those training PDF's had a breakdown of the fuel system. Perhaps someone knows of the correct link and could post it here.
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post #4 of 14 Old 10-17-2015
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This link has a lot of pictures. Perhaps something in it can help you.

https://www.ifixit.com/Guide/Fixing+...Gas+Leak/11326
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post #5 of 14 Old 10-17-2015
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The Touareg Electrical System Design and Function
Self-Study Programme 298

Priming function of electrical fuel pump

The petrol engines of the Volkswagen Touareg all feature a priming function of the fuel pump so that enough pressure in the fuel lines can be built up.

Function:
When the driver's door is opened and terminal 15 is closed, a signal is sent via the CAN bus from the entry and start authorisation control unit J518 (terminal 15 off), a signal is also sent from the driver's door control unit J386 (driver's door opened) and, for reasons of safety, a discreet signal (status of terminal 15) is sent to the onboard power supply control unit J519. This then actuates the relay to prime the fuel pump for approx. 2 seconds. The priming function of the fuel pump is stopped when the ignition is switched on. Continued actuation is done through the engine control unit.

If the driver's door stays open, the actuation is repeated a maximum of three times in intervals.

Timed actuation from the onboard power supply control unit prevents continued actuation of the fuel pump if the driver's door is opened and closed a number of times in short intervals.

Crash shut-off
If with the ignition switched on a crash is detected, a signal is sent from the airbag control unit J234 via the CAN bus and the fuel pump is switched off immediately. After about 5 seconds it can be activated again by switching the ignition off and on.

Electric circuit:Onboard power supply management Key
G6 Fuel pump
J17 Fuel pump relay
J386 Driver's door control unit
J518 Entry and start authorisation control unit
J519 Onboard power supply control unit
J623 Engine control unit
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post #6 of 14 Old 10-17-2015
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Good, helpful research, NickyT.


VW Touareg models are as follows:
Generation 1: T1 is model 7LA & facelift T2 is model 7L6
Generation 2: T3 is model 7P5 & facelift T4 is model 7P6
Generation 3: T5 is model CR7 [Not available in "VW Atlas" North America!]
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post #7 of 14 Old 10-18-2015 Thread Starter
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I can give direct power to both pumps and they both work. I checked every fuse on the vehicle and swapped both 404 relay with others in the ebox. I get no power to the priming pump when the door opens. I scanned and have no codes either.
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post #8 of 14 Old 10-18-2015 Thread Starter
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How can i test the j623 and j519
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post #9 of 14 Old 10-18-2015
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You need somebody with the Bentley cd manual to print out the procedure or to go up to VW site and take out a subscription to the online service manual.

I don't have access to either.

Hopefully someone will have access and print out the procedure for you.

PS: You are in deep enough here that you will have to own or have access to a VCDS if you are going to have any chance of fixing this on your own. If you are checking with codes with an OBD2 scanner, it ain't gonna work out for ya.
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post #10 of 14 Old 10-18-2015 Thread Starter
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Update
I found the issue that I'm having. I decided to take everything apart and trace my steps. Looking at the fuel filter housing i noticed the two hoses on the left and right were full of fuel but the middle hose that goes to the passenger side was empty. I gave direct power to the filter housing and fuel was spraying out of the sides. Taking it apart again the o ring in the filter housing was pinched and not giving a tight seal allowing pressure to build in the housing to send fuel to both pumps. After reseating the oring between the top and bottom part of the housing the pump primes fine and touareg runs great.
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