Return line filter for HPFP?

Is it possible to add a filter on the HPFP return line? I'm assuming that the return line has virtually no pressure (ie, open at the fuel tank), but correct me if I'm wrong. Could you get a cheap inline fuel filter, cut into the hose, and install it?

The return from the HPFP already goes to the filter, then to the tank.

If that's the case, then why the need to replace the tank, fuel lines, etc after a HPFP failure?

You could.
A cheap inline filter would not get the size particles you are interested in stopping, though. (Making some assumptions here, please forgive me if they are unwarranted.) Cheap small inline filters range from 120 micron to about 30 micron - and the ratings do not mean much.

I did put a really cheap filter in my return line, more as a tell tale (hoping to see metal particles if they appeared) rather than in an attempt to save the fuel tank, fuel pump and fuel lines in the event of failure.

MayorDJQ said:

The return from the HPFP already goes to the filter, then to the tank.

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The flow path is often misunderstood.

Though the return goes to the filter housing on the dirty side of the filter, it is normally directed right back out the filter, still on the dirty side, to the tank.
Only fuel going to the aux pump and engine goes through the filter.

If the fuel is really cold the return fuel can be pulled back through the filter to go back to the engine - but not normally.

I know this discussion is valid for the mark V filters with the extra screw on the top and the "olympic ring" seal inside - I am not sure about the other filter housing types that come on Mk V's. This discussion is also valid for Mk IV type filters with the thermo Tee.

This is a photo of a Lubrication Specialist's Mk IV filter head, with a Caterpillar 2 micron filter and some sort of cheap see through fuel filter on the return line. This is mounted on a CJAA Common Rail engine. The return line fuel filter is present more of a hope that it will show metal particles if they start to appear. I think this one had (a rather meaningless) 80 micron rating.

I'm just gonna make all of my fuel lines out of filter material. That'll show that HPFP who's boss!

WVU TDI said:

I'm just gonna make all of my fuel lines out of filter material. That'll show that HPFP who's boss!

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Good call, I've got some extra gauze laying around that I can stuff into my lines!

dpg said:

Good call, I've got some extra gauze laying around that I can stuff into my lines!

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Sounds like a couple of somebodys need some 6 figure engineering jobs at VW!

The return line pressures for 2.0T's I think it 10BAR but I could be wrong.
I think it needs between 8-10 for the injectors to operate correctly after the inital injection, the 10 bar is used to bring the injector back up to shut off the injection sequence.

WVU TDI said:

I'm just gonna make all of my fuel lines out of filter material. That'll show that HPFP who's boss!

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How did making your fuel line come out?