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Discussion Starter #1
Hi all, hopefully someone can point me in the right direction.

I have a 3.0l V6 TDI 7LA with the BKS engine.Recently I tried to start it after it had been sitting for a few weeks and it turned over once before the battery was completely drained. The battery is 4 years old, so no surprises there.I tried jump starting it, and while the engine turned over quite readily, it would not fire. I've replaced the battery as it is most definitely history, but it still just turns over without firing when I try to start it.

Has anyone experienced this before and know how to resolve it?
 

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2005 Touareg - 3.2L BMX
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Is the fuel pump priming when you open drivers door? If you listen when you open drivers will hear a sound similar to that which the power seat makes. You might not be getting any fuel from the pump behind the drivers side access located under the bench seat. No check engine light?
 

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Discussion Starter #3
Pretty sure the lift pump in the tank is not supposed to run when the drivers door opens, it's only supposed to run when the key is turned to the on position - Then it runs for about 30 seconds (I haven't timed it though).

Is there any way of checking the pressure in the fuel line before it reaches the high pressure pump, and also in the high pressure rails using VCDS? Also, what pressures should I be seeing?

The car is due a service. I haven't replaced the fuel filter yet, it's still sitting in its box in my office. Wondering if I should replace that (Following procedure as outlined in Elsawin) and try again?
 

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The SSP is easy to find, if you need more information. I am a petrol owner so I can not verify that the prime function does not exist on diesel, but the guide suggests that. I can verify that it does work this way on the petrol engines.

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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Discussion Starter #6 (Edited)
I appreciate you trying to help, but the diesel system is completely different to the petrol. The delivery pumps (there are two in the diesel tank) do not operate when the door is opened. They operate for a timed period when the ignition is switched on, and continuously while the engine is turning over. The high pressure pump is engine driven so does not operate at all if the engine is not turning over.
 

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Discussion Starter #7
I timed the duration the delivery pumps operate after turning on the ignition - it's 60 seconds. Replaced the diesel filter on the off chance that's it's clogged, and while it was really, really manky, the problem persists with the new filter (Yes, I carefully followed Elsawin, and I did purge the system before attempting to start)
 

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2005 Touareg - 3.2L BMX
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Kind of curious as to why the diesel is different. The petrol has two pumps in the fuel tank that send low pressure fuel to the high pressure pump which then feeds the injector rail. See no reason why diesel operation would be different. The fuel tank is the same odd somewhat U shaped larger (primary)behind driver with secondary smaller side of tank behind passenger each with a pump. In any event still seems like a fuel pump problem. Generally when any car turns over rapidly and won’t start it is a fuel or electrical problem.
 

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Discussion Starter #9
It's started. I just had to crank it for longer (15s) than I'm used to (5s).

Various differences, I don't know if this is because mine is diesel ROW and yours is petrol NAR, but:
1. Pumps do not operate when a door is opened. The do operate for 60s when ignition is switched on but car is not started (you can hear them)
2. VCDS group 035 in the Engine module is supposed to provide a on/off/next button that can be used to run the pumps. It's there, but it it does not run the pumps. I purged the system after replacing the fuel filter by turning the ignition on and letting the pumps run, and I could hear the air purging and also could tell (on the third cycle) when purging had completed, as the pump sound changed frequency.

It's now back to starting after just a second or so. I suspect that due to the age and milage of the car, I will need to replace both the engine speed sensor and the starter motor (Apparently a known issue on these engines) soon.
 

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All of my long cranking problems were related to camshaft position sensors, although I would get error codes for both the sensors and the speed sensor. Unless the speed sensor is intermitent should not cause long cranking. Car wont start or run if speed sensor fails, however car will eventually start with a bad camshaft sensor, usually, just takes forever.
 
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