user113 wrote:
An in-line lift pump works well. There is a possibility of still getting air in the system from the joints at the fuel tank itself, but the in-line pump will help push those through the fuel filter. I am using a Mr. Gasket pump (12D) and it works just fine, way cheaper than many of the others. The cheap Facet's should work as well.
I don't think, however, that there is much of a nexus between fuel economy and a low pressure fuel pump. The fuel pump may cause it to run smoother and quieter, but that's all I would expect.
As to your economy, are you relying on the EVIC numbers, or are you calculating by hand? On the highway (long trips) my EVIC reads 31-32 mpg, going to work it reads around 27, and around town it shows 22 or so. My hand calculated numbers are usually slightly higher. Try hand calculating and see what you are actually getting.
I may just try the inline pump you mentioned here. I have had air in fuel issues on other diesels and it seemed to help my fuel economy as I fixed them. The best example was on an 01 F250. Put the fuel return system and airdog on it and got a smoother, better running and more effecient truck. Wish I still had the thing!
I don't have the EVIC. All my numbers are hand calculated. I am a little disappointed as I have wanted one of these for a long time. I will probably keep it for a hunting vehicle but if the pump doesn't help I may buy a VW Passat. Used to have an 03 Jetta tdi. It was one of the best I have ever owned.