BVCRD wrote:
Why not just find the leak, and stop it up. Can only be coming from a small handfull of places.
Air leaks in the fuel system are inevitable. Hot fuel outgassing "air" is inevitable. Bubble are innevitable. Here's the problem that DCX doesn't seem to see:
Air bubbles will collect UPWARD. On the CRD, all "UP" leads you to back to the fuel filter, so any leak or bubble formation ANYWHERE on the lines before or after the filter still collects air in the filter HEAD in one big "bubble". This is particularly bad with a heating element that sits up there where the bubble will always be, leading to overheating of the element. Over heating leads to parts warping which leads to worse airleaks.
Air accumulation will even happen when the engine is OFF and there is no "suction" from the pumps, because the weight of the fuel in the lines before and after the filter will be "pulling" away from the filter, creating a small but unfortuneate negative pressure in the filter area...encouraging air leaks in the most likely area.
VW puts the filter below the pump, which also might be a bad idea because then air would accumulate in the pump (which we have discussed as a "bad thing".
A visable, high placed air trap (after the fuel filter) would be a simple add-on and a cheap, easy fix IMHO. A lift pump would not be an easy fix and would not, IMHO, "push" out this accumulated air bubble back out the leaks unless the leak was on top of the filter head. Instead, this bubble will go thorugh the engine at WOT...weee what fun. A lift pump would, however, slow the accumulation of air by reducing the time that the lines were under more serious negative pressue. But a lift pump would not stop the innevitable accumulation of air in the filter head.
You can't stop gas bubbles in the fuel lines. But you can trap them.