Fuel filter: ahead or behind the pump
Turbo Mini Forums

Hi,

Should we put fuel filter ahead or behind external fuel pumps ?

I have an external pump running with a carb tank. MPI setup with a 3bar regulator and return path.

All the Bosch/Marelli docs I've seen show the filter behind (after) the pump. However the filter is expected to protect the pump as well.
On my Maserati (exactly the same setup like mine with a carb tank) there is a filter ahead (a small) and behind (the main one) the pump. On Alfa 75 (Bosch injection) the filter is behind the external pump. Same on Alfa 33 16v.

In the book written by the Emerald designer he says to put the filter ahead the pump.

What do you know/think about all that ?

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

Simple mesh filter before the pump, then the main filter after the pump.

This is how the SPi and MPi systems work. There is a mesh filter on the pump like this:



Then i use a filter after the pump:

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

With an internal pump you don't have choice.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

No, but you need to protect the pump but not starve it, hence the coarse mesh filter.

I think that there is a filter on the outlet of a standard tank that will protect the pump, so just put the main filter after the pump.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

The DON runs a filter before the pump. However if you do this you need to make sure that the fuel lines are sufficiently large and the filter sufficiently free flowing to not starve the inlet side of the pump. Fuel line size tank to filter on the DON is 5/8".