[sustdi]

After you replace the fuel filter,a lot of air enters the system which needs to be bled out. If you have the pump or hardlines off, or run out of fuel (i've done it), there is a ton of air in the high-pressure side which will result in very long cranking, and if youve run it dry and your fuel pump isn't toast already, could result in even more damage.

I heard people say that cycling ignition will run the pump, this is not true though.

Does keying ignition on and off without starting engine run the lift pump?
At least on CNRB, No.

Does door-open run the lift pump?
No.

There are two ways to prime with the lift pump, but the best way is by running thru Engine -> Basic Settings -> Transfer Fuel Pump Test in either OBD11 or VCDS which runs it for roughly 5 minutes.

There is also a concern that running the lift pump may not be able to bleed the high pressure side sufficiently or at all (up to the injector furthers from the pump), thus some recommend to crank the car while cracking the nut on the injector furthest from the pump, which for v6/v8 tdishould be done on both sides. There is also suggestion to unplug the rail pressure sensor. Theoretically, both of these will allow the car to crank without starting as the the car will not be able to build pressure in the car. If the car is off when the injector is cracked, there is no risk of damage, and even if you do it while the car is running, I don't believe there is risk.

Cranking the car without the engine starting is also desired for priming the oil system.

I had several rails (feed from HPFP and crossover rail) off of my car and wanted to test if the lift pump will actually push fuel all the way to the injectors. the answer is yes it does. I ran the lift pump and cracked the injectors on each rail closest to the front of the car, and both burped the air out and then fresh fuel came out. so the answer is:

Does the lift pump actually push fuel all the way to the injectors during transfer pump test?
Yes, but for major high-pressure side repairs, I recommend to run TF pump, crack furthest injector and then close them when only fuel and no more air is coming out, then repeat on other rail.

Will Unplugging the rail pressure sensor on a CNRB prevent it from starting.
Surprisingly no it starts right up...

 

[New2Tregs]

Good write up.
Hopefully it'll help those that need the info on re-priming/re-filling the system.

 

[Smendzer]

I just did the fuel filter on my 2012 Cata 3.0 TDI, pulled the top off, sucked out what was in it, removed the old filter, filled with diesel purge and put in the new filter, was nowhere near full after the filter soaked up most of it, top back on, key on key off key on key off key on key off, started right up and has been running just fine since.

 

[SaVAGeSoot]

I just did the fuel filter on my 2012 Cata 3.0 TDI, pulled the top off, sucked out what was in it, removed the old filter, filled with diesel purge and put in the new filter, was nowhere near full after the filter soaked up most of it, top back on, key on key off key on key off key on key off, started right up and has been running just fine since.

You should read the topic\post again... slowly....

 

[Smendzer]

You should read the topic\post again... slowly....

I think you should be more specific about what you take issue with, the title says "after filter OR high pressure" he also didnt specify that it was cnrb, just that he didnt think the key on or door open trick worked on them.

 

[SaVAGeSoot]

The post reads

I think you should be more specific about what you take issue with, the title says "after filter OR high pressure" he also didnt specify that it was cnrb, just that he didnt think the key on or door open trick worked on them.

So are you saying then that your post confirmed that key cycling primed the CATA? Maybe I should read your post slower.....

 

[Smendzer]

The post reads

So are you saying then that your post confirmed that key cycling primed the CATA? Maybe I should read your post slower.....

Well I didn't use vcds to prime it and I had no issues on start up or running it for about 15 minutes after changing the filter.

 

[ToolmanJohn]

I've never used VCDS to prime the fuel system after a fuel filter change either. I just fill the fuel filter cannister with clean diesel from a small one gallon container, or top it off with Diesel Kleen additive (I've done it both ways a few times) , then replace the bolts, and start it. Never had issues.

 

[volkswagens-for-life]

Fill the fuel canister up with diesel purge

 

[sustdi]

letting your HPFP dry hump itself after a fuel filter change isn't the flex some people think it is

 

[sustdi]

I just did the fuel filter on my 2012 Cata 3.0 TDI, pulled the top off, sucked out what was in it, removed the old filter, filled with diesel purge and put in the new filter, was nowhere near full after the filter soaked up most of it, top back on, key on key off key on key off key on key off, started right up and has been running just fine since.

When you say key on key off you mean you let the car crank and kill it before ignition starts?

 

[Smendzer]

When you say key on key off you mean you let the car crank and kill it before ignition starts?

Nope, just ignition on ignition off a few times. Never hesitated, coughed, stuttered, bogged, anything.

 

[sustdi]

Nope, just ignition on ignition off a few times. Never hesitated, coughed, stuttered, bogged, anything.

With foot on brake?

 

[Smendzer]

With foot on brake?

Nope, it likely would have started right away if I had done that.

 

[sustdi]

Yeah that didn't seem to run the pump on the CNRB at least that what i saw which is why i made this post

 

[icrashcoolcars]

UPDATE FOR CATA 3.0 TDI:

cycling key primes the pump. I physically had my hand on the pump while my gf cycled the key to the “on” position without starting, and everytime felt the pump whir for about 5 seconds, and could see some of the rubber lines swell a tiny bit form the pressure. After a few, I’d crack some fuel lines to let air out while she did it, almost like bleeding brakes.

this worked on my 2010 CATA Touareg.

not trying to hijack the thread, just posting definitively for the CATA guys. Again, mine is 2010, not sure if maybe some oof the earlier ones were different, but I doubt it.

 

[sustdi]

it works on cayenne as well .

 

[bollarichards]

Good morning everyone, I have a 2008 VW Touareg V6, can someone please help me the car sometimes had trouble starting and went into limp mode, mechanic came to check and said it was the diesel pump, He took the pump off and sent in, Bosch services tested the pump and found the suction control valve faulty, it was replaced, the pump was tested again and was 100%, the pump was put back, he primed the system by cycling the ignition key to allow the low pressure pump to push fuel through and remove any air pockets by loosening injector lines to allow air to escape while cranking the engine. It still doesn't want to start at all, the battery is dying very quickly, please help

 

[New2Tregs]

Good morning everyone, I have a 2008 VW Touareg V6, can someone please help me the car sometimes had trouble starting and went into limp mode, mechanic came to check and said it was the diesel pump, He took the pump off and sent in, Bosch services tested the pump and found the suction control valve faulty, it was replaced, the pump was tested again and was 100%, the pump was put back, he primed the system by cycling the ignition key to allow the low pressure pump to push fuel through and remove any air pockets by loosening injector lines to allow air to escape while cranking the engine. It still doesn't want to start at all, the battery is dying very quickly, please help

Did you get any contaminants in the system?
Did you change the filter also?

 

[bollarichards]

Yes but didn't change the filter, mechanic took the pump off again because it shows on the dinostics has pressure but drop fast so he took the pump back to Bosch service