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Parts needed for installing longer fuel line from stock FPR to hard line?

80K views 245 replies 45 participants last post by  chechem84 
#1 · (Edited)
I've searched extensively on what seems like a pretty simple question, but I haven't found any definitive answers. :p

I'm looking to install a longer fuel hose from my stock FPR to my stock hard line (to solve the "GR stumbles at 2500-3200rpm" issue.) Everything in this area is stock. I know I need a simple fuel line tool to remove the quick-connect on the hard line end. I'm thinking the cheapie plastic ones from Harbor Freight should do the trick.

Once that's off, what else do I need on the quick-connector side? The stock connector has a crimped metal piece on it. Will I need to hack out the fuel line side of the quick connector to re-use it or should I just buy another one? I haven't been able to find a part number for the quick connector. Two different local Autozone-ish places had squat, too.

Edit: Pic:

 
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#3 ·
Thanks for the reply.

So I'll use a disconnect tool to remove the connector, throw away that fuel line and that metal fitting, then just get new fuel line and use one of these in the end of it?

Dorman Fuel Line Connectors - SummitRacing.com

Basically, the black plastic Dorman quick-connector on that site will replace all the metal (and the green plastic) in my photo, right?
 
#6 · (Edited)
There's about a 50/50 split of people that have success from that kit, and people that have no change with the kit. The simplest solution is actually extending the fuel line as I'm doing. It seems like this solution (and the 100% success rate it has so far) has just come up on here, nasioc and romraider in the past month or so.

It turns out that the problem is caused by a resonance wave (or standing wave, I'm not sure I'm using the correct term) in the fuel line at certain RPMs, for larger-than stock injectors. I believe there's also load compensation data in the stock tune indicating Subaru has done work to tune around the mechanical issue. Doubling the size of the injectors means you and I are making the mechanical problem way worse and therefore, way harder to tune around (which is what a lot of people have been working on for a while.)

Thanks for the link, though. I was pretty close to just throwing the $200 at the problem. Even with my modest 350whp 20G-XT setup, I have to very deliberately drive around the flat spot. Otherwise, the car lurches and makes me sad.

Edit for interesting trivia: The plumbing term for what is happening in the stock fuel line in this situation is called water hammer.
 
#7 ·
Are you extending both the return and supply hoses? you mentioned the hose to the FPR which should be the return. Unless im mistaken, the pic above looks like the supply line.
can you take some pics of what you end up doing and the parts? I wouldnt mind giving it a shot to see if it helps, tuning definitely took care of most of the stumbling but its not 100% as I would like it to be.

Thanks!
 
#8 ·
I'm definitely extending just the supply hose, which is what I've taken a pic of. It sounds like I said FPR when I was actually referring to the fuel dampener? Whatever is the stock piece that the supply line comes out of (and heads straight to the hard line, as pictured) and looks like it has a plastic jimmy hat on the top of it.

EVERYBODY SHUT UP I TOTALLY KNOW WHAT I'M DOING. :D

Will post pics when I'm done.
 
#9 ·
Also, i think once you get that quick connector off, you might find that you have enough hard line to install a fuel hose on it and clamp it down......negating the need for a barbed quick connect. I cant verify that though since ive never taken it off. but if its anything like the wrx one you should have plenty. Check out pics at this link.

How to remove fuel disconnect? - Ultimate Subaru Message Board
 
#10 ·
I did a little search, looks like you wont need any type of quick fitting with a barb after removing the stock inlet line, kinda looks goofy though with all that extra fuel line just coiled up. I wonder if a universal fuel filter tapped into the stock inlet line would serve the same effect to reduce the resonance wave. I might try both out...

see pic at middle of page linked below

RomRaider • View topic - How to fix the GR STi 2400-3200 stumbles
 
#11 ·
After buying (but not installing) the parts this morning, it does look like all I really needed was the fuel line and the same simple metal clamp that's on the other side of the line.

As for adding a universal fuel filter: I'd think a longer fuel line is a better solution because it's simpler, cheaper and will never clog. I wasn't psyched about that coil, but if it resolves most of the drive-ability issue, I'll be too busy hauling ass to even think of it. :)

But yeah, that RomRaider thread has been my jam. You can even see my retarded "plz help!" post at the end there. Kind of a bummer that it took a few days for the mods to approve that.
 
#16 ·
Im sure you already know this, but remember to release the fuel pressure before taking off that line unless you want a 93 octane bath. Pull the fuel pump fuse from under hood while the car is running and let it stall out. You should be good to go after that!
 
#17 ·
OP, just a side note for you. i recently did this 4 days ago using 2' of 5/16" fuel line i bought from a local pep boys auto center. coiled it all around i believe there was 3 coils, although i left oem connection intact and just tied into oem hose w/ a barbed coupling then onto feed line dampener. beware of using the normal fuel line from generic auto places. My extra line actually burst with in 4 days. Not sure whether it was do to being coiled up and extra pressure on that hose, i had 3 zip ties loosly keeping it coiled, or just bad luck. the generic hose labeled as fuel line did not have a psi rating or anything on it. i replaced today actually when it burst on start up w/ heavy duty gates fuel line, it is the 4AN braided fuel line and rated to 300psi. and only has 2 coils between the connections.

i also read that some people have taken the oem feed dampener off and either used a inline tee for the connection of feed and balance line. and others have removed feed dampener and used barbed coupling, and capped off balance line going to return fpr.

As you stated i also heard that the kits you can buy sometimes didnt help peoples stumble issue, and i dont have the $ atm to do a complete fpr setup w/ parallel rails, which also will solve this stumble problem. Hence why i went searching all over till i found the same write up on rom raider, and went the cheaper route for the time being.

either route you go keep an eye on the fittings and fuel line coiled up, mine was very soft after i removed it almost like it had been stretched and broke the internal reinforcement.

also please keep us all posted on the route you go, and update after awhile so others can also have options and feedback on this.

and remember to pull fp fuse in the fuse box under the hood, remove fuel cap and run car till it dies to relieve as much of the pressure as u can, you will still have some so have a towel wrapped under all the lines so fuel dont spill down your motor and fuse box. but it does stop after a few seconds.. when all done replace fuse tighten fuel cap and prime the fp a few times to check for leaks b4 starting..;)
 
#20 ·
OP, just a side note for you. i recently did this 4 days ago using 2' of 5/16" fuel line i bought from a local pep boys auto center.
Sounds like you bought normal fuel line/hose when what we need is fuel injection line/hose, which is rated for much higher PSI. The stuff I got and linked a few posts up is fuel injection line rated to 225 PSI.

I'm curious why you would spend $200 to swap in a FPR and fuel dampener when the extra-long fuel is actually the solution that works. The GR's FPR and dampener work fine otherwise. *shrug*
 
#18 ·
based on your comment that it didnt have any psi rating on it and that it was very soft when you removed it, you probably ended up purchasing something other than fuel line.....and the fuel broke it down causing it to burst.
on another note, did it have any effect on the stumbles for you?
 
#19 ·
the line i originally had purchased was labeled on tag and on the hose itself as 5/16" fuel line.. yes it cured the stumble issue completely. although i do not feel comfortable leaving it that way forever, due to being a temp band aid. it does seem to work extremely well for the time being and as long as there is no other side effects all shall be ok. this is however just my opinion. i do plan on replaceing the known 08 fpr and dampener flaw after the holidays and winter..
 
#22 ·
I had the older style STi fpr and damper setup on my car installed at my tuners shop. It didnt cure anything, some additional tuning did smooth it out some but not completely. Based on other peoples experiences, im willing to go back to the stock fpr/damper setup and try the longer hose deal. If it works, im keeping it that way ;)
 
#23 · (Edited)
Ok so I removed the older style STi fpr and dampers and reinstalled the stock 08 fpr and damper setup. I took off my stock inlet line from the fuel damper to the hard line inlet and installed 3' of 5/16" high pressure fuel injection line. Im not too crazy about having 3' of fuel line coiled up in the engine bay but I made sure its out of the way of any moving parts or areas where it can rub. I got on the highway and using light throttle went through the stumbling rev range (2800-3400) in 5th and 6th gear and it accelerated smoothly. I would like some more seat time as there was a lot of traffic but it does appear that the stumbles are gone.
Just a note - if you do this make sure you purchase the correct fuel injection hose and that it states as such on the line itself. I asked one of the counter jockeys at Autozone for 3' of fuel injection hose and he came back out with regular fuel line. When I asked him about it, he took me to the back and there it was in plain sight --- 5/16" fuel injection hose.
 
#31 · (Edited)
I don't like adding 2 more connections to the fuel line like Avrgmike did. Nor am I a fan of using worm-gear hose clamps for a fuel injection line. (I used clamps identical to stock.).

However, I would add this: You couldn't use a hose/fuel-injection clamp on the hard-line anyways because the hard-line doesn't have a flared end. The fuel dampener end does, which is why the stock setup uses a hose clamp there.

The standard solution that I've gone with doesn't break anything when you remove it. So, if you wanted to go back to stock, you'd just undo 1 quick-connector and one hose clamp and swap the stock quick-connector and hose clamp + line in. 5 minute job, tops.
 
#26 ·
Yea. That's why I left it alone,that n it's easier to pull it apart n go back to stick if need be ;) I've had no problems since switching to the high rated line. Met w my tuner black Friday and did road tuning w/ a bunch of 3 rd n 4th pulls, along w/ 1-5 pulls and no leak or swelling. Tyvm Ray@turbotektuning my baby is extremely smooth n happy now.
 
#29 ·
Here's the connector and clamp I ended up using. Everything seems to fit, except the new connector has a tiny bit more movement once it's fully installed. I also noticed (because I had forgotten to slide the metal clamp on the line before plugging the quick connector in) that the connector I got actually lets you push the black plastic piece in to disengage the internal clips so you can release the connector. The stock green one did not do that.

 
#30 ·
Also, you don't need to buy a disconnect tool to get the stock green quick-connectors off. You can just slide two large zip-ties into the green connector (90 degrees off of the two divots/marks visible on the lip of the green connector) and you'll disengage the internal clips just like a disconnect tool. No breakage, no stress on the connector at all. Definitely a zero-damage method of removing that connector such that it would be re-usable. (The new one I got is built just like the stock one internally. The main difference is in the black plastic quick-connector clip on the new one.)

 
#32 ·
Utah, tyvm for the comments. And also the picture of the napa part you used. I will definitely be switching to that, this way there's 1 less spot ( barbed connector) to worry bout leaking. Also it's a lot cleaner look. This is the great thing about forums ;) everyone has input and technique
 
#34 ·
Awesome update, rube23. Glad to hear it worked out for you. You're a braver man than I am, pushing that fuel line over the hard-line's quick-connect ridge like that. ;)

I've got other work on-going with my car at the moment, so I'm thinking about switching from my Walbro to a DW200 for a quieter fuel pump, while the fuel system is already de-pressurized...
 
#36 · (Edited)
If you go to the last page of the romraider thread, someone put two dampers on the inlet line and that seems to cure it.

EDIT: I'm a skeptic until someone actually uses this setup (2 dampers) for more than 100 miles. I will probably try the 2 dampers on the inlet line, but I don't understand why 2 are needed.
 
#37 ·
Why would anyone choose the more complex, more expensive solution that also has more connections? I just don't get that. 3 feet of fuel line sounded like a ridiculous and clunky solution to me, but you coil it 2 times and tuck it in and it's not noticeable unless you're looking for it.

I'll take a picture of my fuel-line setup tonight.
 
#42 · (Edited)
I found this way the easiest to Eliminate the Lean Stumble which Romraider guys have dons as well. Just buy 8mm Fuel line 3feet long and run it from Damper to Fuel rail. simple. No connectors needed just use the old clamps.Get your tuner to Zero out Load compensation tables and adjust from there. Wont need much adjusting though.

 
#43 ·
I found this way the easiest to Eliminate the Lean Stumble which Romraider guys have dons as well. Just buy 8mm Fuel line 3feet long and run it from Damper to Fuel rail. simple. No connectors needed just use the old clamps.Get your tuner to Zero out Load compensation tables and adjust from there. Wont need much adjusting though.
You know that's exactly what this entire thread is about, right? :eek2:

Also, there are no "old clamps" on the hardline side for stock GRs. It's a quick connector. As you'll see in the pics. That I posed. In this thread. ;)
 
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