[Boosthund]

Happy New Year.
I own a 2005 VW Passat TDI w/ almost 100k miles.
I have replaced the balance shaft module, aftermarket axles and everything seems to be running well w/ one exception: about a 1/3 decline in fuel mileage.
During BSM replacement therapy, I had water pump and timing belt replaced ... this was over a year ago. Recently installed new gas tank. Decrease in gas mileage has happened recently. I will be changing air filter, but am wondering if it is anything else.
Thanks.

 

[chittychittybangbang]

Welcome! I don't think it's due to the balance shaft module or axles.

1/3 decrease in fuel mileage is major. Did you change tires? There's a FAQ article on how to check and adjust camshaft timing (torsion value) but if it's off it won't cause a 1/3 loss in mpg.

When you turn the key on can you hear the fuel pump in tank running?

 

[Boosthund]

Symptoms

Welcome! I don't think it's due to the balance shaft module or axles.

1/3 decrease in fuel mileage is major. Did you change tires? There's a FAQ article on how to check and adjust camshaft timing (torsion value) but if it's off it won't cause a 1/3 loss in mpg.

When you turn the key on can you hear the fuel pump in tank running?

Thanks Chitty...

No change of tires, and yet to put the vag-com on to see what the T-V value is.
I did just have the fuel tank replaced as it failed. Early on I had rust near the filler cap, but but I'm told that that wasn't the problem this time around. I would fill the tank and find a quart or 2 of fuel on the ground under the car ... ahh, nothing the smell of diesel when you least expect it!
I just checked for that funky noise that I used to hear with the ignition on, GP light still on, but before I turned over the engine ... didn't hear it.
Might that be the problem?

Looking forward to benefitting from your valuable site.

Happy New Year,
Paul V.

 

[chittychittybangbang]

Maybe. Lift the trunk area and have a helper turn the key to ON while you put your ear to the pump and feel it for running.

FYI, the fuel tank is mostly plastic. Here is a video showing it out of the car: http://www.myturbodiesel.com/1000q/a4/vent-fuel-tank-FAQ.htm