[s-cars] Fuel Pressure Regulator R&R

[David Giannandrea]

I don't think changing either FPR or filter will fix a non-starting urS4. I
do believe the car should still start.  A plugged fuel filter would starve
fuel at high loads. A failing FPR might be similar, not providing enough
pressure to flow enough fuel at high loads.

Regardless, fuel filters are cheap ($12). The fuel pressure regulator (FPR)
might be a bit more expensive if you buy from Audi. I bought aftermarket and
didn't like the smaller outlet port, returned it, bought from Audi. But I
was being overly conservative about wanting enough fuel to flow. 

Regarding the fuel pump, I again returned the aftermarket pump because of
two differences. Aftermarket required a minor modification to the connector
and it was substantially lighter in weight than the original.  So, once
again, I returned the pump for the Audi part. Not that the pump would not
have worked. I'm sure it would have been able to supply the necessary 4bar
of pressure...most of the time. I was again concerned about it's ability to
provide 4bar at high flow rates.

Regarding the fuel pump, you can give it a limited test by letting it run
fuel into a can. It's supposed to have a something like a gallons/minute
rating. BE VERY CAREFUL. You're working with spark and gasoline here.

David G.