Relocating Fuel Filter Under Hood and Deleting In-Tank Filter.

Has anyone successfully bypassed or deleted the in-tank fuel filter and installed one under the hood? I'd like to figure out a way to do the bypass then I can install a filter with AN-6 fittings just before the fuel rail.

 

I found a thread where the STI guys have figured out a way to do this, but they have a different style of in-tank filter. I suspect it is going to be a little more difficult with the LGT filter because it is part of the housing that the fuel pump mounts to.

 

Here's the link to the IWSTI thread, see post #15.

http://www.iwsti.com/forums/2-5-liter-litre-factory-motor/191712-deleting-tank-filter-relocating-under-hood-2.html

I guess you could cut the filter off the intank one and then install your inline one. It should be easy if your good with fittings.

 

While the pumps out might as well do a DW65c too.

I don't know why you would delete the filter at the pump.

 

Its basically a fine mesh screen, and don't think it impacts fuel delivery other than protecting your pump from ingesting grit (which there definitely was in my fuel pump housing).

 

But if you REALLY want to delete it, you can just take the screen off the pump.

 

And, at one point I actually installed a basic metal canister in-line fuel filter in the fuel delivery line, partly because I didn't like the fact that there wasn't a "real" filter before the injectors and also to provide some pulse dampening to the fuel circuit.

 

I took it out about 6 months later because it was getting so hot that you couldn't touch after cruising on the highway. No sense in super heating the gas before it hits the rail. IMHO.

there's a filter in the pump housing. why not replace just that? 42072AG140

I installed a DW65C to support my BNG 20G/TD05H and I'D 1000'S. Then when I called Cobb Tuning Surgeline to schedule my tune they suggested that I should not only replace the intake screen on the pump but also the actual fuel filter that resides inside the housing in which the pump is mounted.

Here's a pic of a used filter that's been cut open. I lifted it from this thread over at iwsti. http://i859.photobucket.com/albums/ab157/smitty5788/IMG_0528.jpg

 

So that got me thinking, it's about the same price for the stock replacement as it would be for a nifty inline AN-6 filter I could mount under the hood. It would go nicely with the new fuel regulator that Cobb also suggested I buy. Which by the way I'm think about getting the Fuelab 53501-1. what's your opinions on that regulator?

 

I'm thinking I could just drill out the plastic assembly above where the pump mounts and put a hose on the pump outlet that runs down to the tube which exits the assembly, effectively bypassing the stock filter. In the pic above you can see there is a hole where the pump discharges up into a channel which directs fuel into the top of the filter. I'd just oversize the hole and put my discharge tube straight onto the pump. The part I haven't figured out yet is where to attach the other end of the tube. Probably not hard to figure out once I have it in front of me. I've read it's best to have the filter as close as possible to the injectors to eliminate any chance of contamination between the filter and injectors. I realize that it's pretty far fetched that there's going to be any contamination with the hardline between the two, but you never know.

Edited August 15, 2014 by elgin.owens

The risk of contamination between pump and injector is very low, in my opinion the best is to have the filter somewhere between pump and any pressure regulating equipment so it won't cause any problems with that. Any contamination in the line between pump and engine is likely from assembly, and if you have used the car it shouldn't be a problem unless you get some new introduced when you mess around.

 

And don't mess with the intake filter to the pump, that will just cause you to need a new pump sooner or later.

I'm wanting to do this myself. One of the added bonuses is more fuel near fuel rail (since extra is stored in the old styled fuel filter), this could help reduce random leanness. I guess I'll plan on doing that around the time I do my fuel pump.

 

You would want to bypass the filter after the pump, don't touch the one before the bump or you will burn it up. This post shows it best. Make sure to use fuel injection hose ($7 per foot), not fuel hose ($2ish per foot), because fuel hose is meant for less pressurized carburetors.

I don't have any intention of messing with the pre-pump filter only the post pump filter will be bypassed.

 

Covertrussian - Unfortunately the thread/pic that you linked to is the STI or older WRX style pump assembly. In the new WRX and 4TH gen legacy they use an assembly that is entirely made of plastic there is no metal bracket. The pic that I posted shows the plastic assembly which houses the pump & filter on the LGT. I wish we had that metal bracket style assembly because it would make the bypass way easier.

 

I'm going to remove the pump assembly from my car in the next few days and see what it will take to do the filter bypass. Hopefully I'm able to figure something out because I'd love to make a tutorial as my way of giving back to this community. I've learned soo much from the people here and all of the tutorials they have created that it's the least I could do.

Sweet, definitely take some pics and post them here as you mock with it, I'm curious myself too. I'm worried that getting rid of the filter will cause flow & pressure issues due to big open space.

interesting, wish I had realized there was another filter in that housing assembly the two times I've had it out. Also wish it wasn't $75 to replace.

It's $75 just for the filter, or is that the whole assembly?

 

EDIT: I'll be darned, part #42072AG16A $75

Edited August 15, 2014 by covertrussian

You don't want to get rid of the screen in tank. It's there to protect the pump from large damaging pieces of foreign debris.

 

Nothing wrong with putting g a fine filter before the rails. But I'd spend my money on an oil feed filter first. If you did already the your set.

We are not talking about replacing the prepump sock, we are talking about the post pump one.

 

Seeing how the fuel pump is in this thread, I think I might be able to bypass the factory filter altogether...

Edited August 15, 2014 by covertrussian

Yeah I wish I had known that I was holding the filter assembly in my hand when I mounted my DW65C inside of it, lol. I didn't get around to working on it yet, but here's a pic I took during the DW65C install, looks like it should be pretty easy to figure out a way to switch up those tubes so they bypass the filter.

 

Can anyone tell me what each of the 3 tubes are that attach to the top of the pump assembly?http://i216.photobucket.com/albums/cc228/elginowens_photos/IMAG1133.jpg

Edited August 16, 2014 by elgin.owens

Thanks Subaru for making something usually very simple to be overly complicated. I'm gonna have to dig through the fsm to find a way to bypass the stock filter.

Cost me about $90 for one of those filters here in Australia.

I'm interested to see if anyone performs the relocation and where/how you mount the filter in the engine bay.

Posted on NASIOC since there are a ton of people there with newer WRX's with the same filter.

 

To reiterate on two ideas on how to solve this. First install Inline filter in engine bay then...

 

1. Gut the filter, reglue the lid and put it all back together.

Issues:

Glue can get undone = loss of fuel pressure

big empty space = requires a lot more power from fuel pump to pump that much volume of fuel

 

2. Run a fuel hose from the pump to the feedneck.

Issues:

There seems to be two exists on the stock assembly not sure why and FSM is not useful. I'm trying to get my hands on a stock assembly to see how it works.

aside from the cost of the filter, is there some other issues with it I am missing?

Cost and difficulty of replacement is the main thing. Older cars always suggested yearly fuel filter replacements, all of the sudden Subaru makes a magical metalic filter that never needs to be replaced right? Not, they used paper that deteriorates with age.

 

Another problem is we don't run 100% gas anymore, e85 is known to clean out your tank & lines and deposit all of the crap into your fuel filter, but it's also hydroscopic (gathers water) and with water the paper elements break apart and clogs your injectors. e10 is not as bad, but still overtime can have the same effect.

Edited August 19, 2014 by covertrussian

I found something useful in my research... If one were to run hose from the pump to feedneck, one must choose the type of hose carefully because not all fuel hose is designed for submersion in fuel.Standard fuel injection hose carried by autopart stores is only SAE R9 rated.

SAE 30R7 is for low pressure, fuel inside only (return lines and carb feed lines)

SAE 30R9 is for high pressure, fuel inside only (feed lines in engine bay and hoses externally around fuel pump)

SAE 30R10 is for high pressure, submersible. (use for In-tank plumbing).

 

I'm thinking the two exits on the stock assembly have to do with the jet pump which transfers fuel over the driveshaft tunnel, between the two sides of the tank. See this info from Subaru. Also worth noting is that there is another intake screen/filter on the jet pump, similar to the intake screen/filter on the primary pump.

Good info on the fuel lines!

 

As for the jet pump, that was a very interesting system indeed, I saw it in the FSM and was confused why there were two fuel level meters. After seeing the fuel tank design (and drive shaft being in the way) it made more sense.

 

I don't think it's the jet pump, because the side with two holes is post fuel pump, as in under pressure. If it was from Jet pump you would be pumping fuel into the other half of the tank. I'm working on getting my hands on a whole assembly to figure out how it all works.

MDTURBO did a great write up about 10 years ago about how the fuel system functions, unfortunately the pictures have gone missing. Even without the pictures some useful info can still be salvaged from his thread. http://legacygt.com/forums/showthread.php/mts-fuel-pump-project-24003.html

Here's a diagram showing the plumbing for the fuel pump and jet pump. http://i216.photobucket.com/albums/cc228/elginowens_photos/FuelPumpPlumbing-1.jpg

That picture is a little deceiving. It makes it look like the Delivery and return hoses dump into the jet pump assembly. Looking at the FSM images carefully I noticed that they are just connected to the hard lines that go to the front of the car by the jet pump.

 

Took some screenshots and tailored them excluded cruft.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/General/Fuel%20Pump/FuelTankDesign.png~original

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/General/Fuel%20Pump/FSMDiagram_FuelHoses.png~original

 

Jet pump design

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/General/Fuel%20Pump/FSMJetPump.png~original

 

Just found out that Y return line design is actually off the 04 and older Legacy's, Subaru sucks at updating the FSM with proper information. The 05+ concept might be similar but implementation looks nothing like that.

Edited August 20, 2014 by covertrussian

Looks like the secondary plug is actually a plug and nothing more!!!

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/General/Fuel%20Pump/CIMG1361.jpg~original

 

Here is the secondary port in question, yes the oring is that deformed... this fuel pump was probably leaking fuel pressure because of this...

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/General/Fuel%20Pump/CIMG1360.jpg~original

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/General/Fuel%20Pump/CIMG1366.jpg~original

 

Sadly to get to the filter I had to really destroy the top cover.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/General/Fuel%20Pump/CIMG1371.jpg~original

 

Here's the filter, typical paper element. This is a 30k mile filter btw...

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/General/Fuel%20Pump/CIMG1375.jpg~original

 

Plug in place

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/General/Fuel%20Pump/CIMG1378.jpg~original

 

Sadly there is also not much working room, for wiring the fuel pump directly to the feed line.

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/General/Fuel%20Pump/CIMG1383.jpg~original