Fuel Filter & Pump Swaps

The silver S4 got a new fuel filter and fuel pump.

Audi B5 S4 Fuel Filter Swap
Audi B5 S4 Fuel Filter Swap

Neither of these is a task I enjoy doing, and when the fuel filter started leaking gas after being tightened to the advertised torque I was not happy.  Finding that I could not fit a wrench between the banjo fitting and fuel filter had me even more steamed.  Unable to find a suitable wrench I had about resigned myself to shopping for a new wrench with a thin body when I thought I might be able to get a good grip on the fuel filter with an oil filter wrench.

That hunch turned out to be a successful idea and the extra little bit of tightening the banjo bolt stopped the gasoline leak.

This car is also receiving a fuel pump upgrade with a ProjectB5 setup.  The fuel pump turned into a bit more effort than the “drop-in” name would suggest.  For the life of me I could not get the pump holder to engage with the basket.  This is the fourth time I have swapped pumps in one of these S4s and the first time I have had a hard time getting the pump in place, other than the first when I had not yet purchased the Schwaben fuel pump removal tool.

After 45 minutes of trying, and cursing, I decided to pull the pump out and try to figure out why the darn thing would not lock in.  Comparing it to the recently removed stock unit I noticed that the sock on the bottom of the PB5 pump seemed to to extend a little further than the stock part.  I pulled out the calipers to measure and sure enough the PB5 setup extended down 17 mm further than the stock part.  While the location makes it hard to be conclusive about the cause, it seems likely that the added length is preventing the fuel pump holder from descending far enough into the basket for the notches to engage properly and hold the pump firmly in place.

The next hurdle was a do-over on my part as I forgot that Audi wires the fuel pump backwards, the RED wire goes to the negative post and the BLACK wire to the positive post.  I wired up the normal way and got nothing when I tried to start the car.  Out came the pump so I could swap the wires, but happily upon re-installation the car started right up.

The car is on the base tune but is looking pretty good thus far.

CP Initial Boost Profile
Initial Boost Profile