WARNING / HOW TO: Fuel Line Return (High Pressure)

Clipse3GT · Mar 9, 2010

This is an Update to below:

"Originally Posted by Clipse3GT View Post
Update!!!

BOSCH 044

I enlarged mine to 3/32's or 2.4mm because of the new BOSCH 044 pump I am running to keep pressures down. It settle around 50 psi base pressure.

Walbro 255 or similar.

Okay, I did more research. I think I came with a severe issue.

If you drill this hole out to 5/16" it will be way too large.

It will cause not enough pressure to be driverted to the hole that connects to the blue connector on the fuel assembly holder. So what does this mean? It means that blue connector causes a "swirling effect"/"venturi pump effect" which will not suck fuel the other side of the tank. Meaning you will run out of fuel 1/4th to 1/3" tank of fuel left. Scary on the highway.

The porting does not effect this effect. However, removing that restrictor does.

The fix is to get some aluminum rod. cut about .125" off drill a 5/65th" hole in the middle, then start filing away the sides to make it fit the hole. Luckily if you used a 5/16th earlier, it leaves a step, which now inturn you can insert the restrictor pill and press it in. Solves the issue and restores the venturi pump effect intank.

Correct size should be 5/64th or 2mm for Walbro 255."

---------

There is a potential for having very high fuel pressure in the EVO X if the stock fuel system is modified.

The reason for this is the stock fuel pump assembly return line flaw...

I upgraded my fuel system with the following...

Upgraded fuel rail, injectors, fuel lines AN 6 feed and return, return line AN 4 to hard line, inline fuel filter, 1:1 fuel pressure regulator, walboro fuel pump.

What started to happen is a very high fuel pressure... of 80+ psi at the FPR.

STOCK: 38 PSI with VAC
STOCK: 45-50 PSI with NO VAC

My reading = 80 PSI (something was not right)

After getting to do the fuel pump assembly installing the new fuel pump and FPR I was still getting 80 psi...

After much searching (with help of theSIN) we figured out why...

1.) You need to take out the fuel pump assembly and all the goodies inside... there is multiple how to's refer to those for the steps.

1.) There is a restriction in the fuel return housing part. There is a 3 way connector. One hole has a pin hole (literally) in it. It has to be enlarged in order to accommodate more flow (larger lines, higher flowing fuel pump). Here is a after the enlargement picture.

Need a 5/16" drill bit & drill to enlarge it.

2.) The fuel return line has a FILTER!!! I know WTF is what I thought as well. It is miniature. Maybe like 4mm in size. It sits in the fuel return line assembly (you need to take off the fuel hose to see it or unclog it). If this filter gets clog it will cause your fuel pressure to sky rocket.

Here is the picture of the filter... It was clogged with this rubber gasket (not sure where it came from).

Also in the same connector there is a spring with valve in it. I believe it is a pressure relief valve. I opted to keep mine functional however. I did port the passage with a 5mm drill bit.

Pressure Relief Valve Apart

3.) I also ported 3 of the 4 passage with a 5mm drill bit to enhance flow.

TOP

SIDE

BOTTOM

Picture of Setup

Clipse3GT said:
Update!!!

BOSCH 044

I enlarged mine to 3/32's or 2.4mm because of the new BOSCH 044 pump I am running to keep pressures down. It settle around 50 psi base pressure.

Walbro 255 or similar.

Okay, I did more research. I think I came with a severe issue.

If you drill this hole out to 5/16" it will be way too large.

It will cause not enough pressure to be driverted to the hole that connects to the blue connector on the fuel assembly holder. So what does this mean? It means that blue connector causes a "swirling effect"/"venturi pump effect" which will not suck fuel the other side of the tank. Meaning you will run out of fuel 1/4th to 1/3" tank of fuel left. Scary on the highway.

The porting does not effect this effect. However, removing that restrictor does.

The fix is to get some aluminum rod. cut about .125" off drill a 5/65th" hole in the middle, then start filing away the sides to make it fit the hole. Luckily if you used a 5/16th earlier, it leaves a step, which now inturn you can insert the restrictor pill and press it in. Solves the issue and restores the venturi pump effect intank.

Correct size should be 5/64th or 2mm for Walbro 255.

BigT · Mar 9, 2010

Are you sure it wasn't just the clog? I know in 2g dsm's, once the fuel pump is upgraded, you need to drill a larger hole somewhere. Its on part due to having a saddlebag fuel tank.

Clipse3GT · Mar 9, 2010

I first drilled the larger orifices (step one) reinstalled the assembly. It dropped my fuel pressure 60 psi. Still too high. I went searching and the return line filter was clogged. So if you do any work on your fuel system it is very possible to clog the return line. The filter is tiny. So anything small will clog it no doubt.

goofygrin · Mar 9, 2010

WTF

Rogue · Mar 9, 2010

Kris... nice writeup!

TheSin · Mar 9, 2010

I had both of the same problems, though I only drilled mine with a 5/64th bit, very very small and I testing it with 40psi of air and it still created good suction from the hump.

I first unclogged mine return line though, and it helped lots I went from 80-110psi (which would pop the return line off the pump housing, to about 45-50, but I still couldn't get it low enough to set it to factory pressure, that is when I went further and figured out how the return worked, once I drilled out that pin hole a little (5/64th) I was able to get 30psi (which the car hated

) but then I could set the pressure with the regulator which is what I wanted, now I'm 42psi without vac and 38psi with at idle and it purrs. And if I need more later I know i"m in control of it.

Also I have -6AN on both sides, just for comparison. And I was extremely careful about debris but somehow that filter still got full, mine was more like dirty then a gasket though

Glad you got it working though! That little filter really messed me up when I found it, I was like what the hell, it's in a line that can't be reused, what a stupid place. Thanks to JNZ for the new lines BTW! Trying to use rubber hoses in there was stupid of me

It's too tight and harsh angles just keeps kinking.

Clipse3GT · Mar 9, 2010

Yeah, I think if you have a adjustable FPR you can use 5/16 and just make it really free flowing. If you have a stock FPR using a smaller bore might be a good idea something like 5/64th's.

No ill effects... drives perfect. Plus my AFR is much more stable at WOT with a better FPR.

TheSin · Mar 9, 2010

perfect I might open mine up and drill it out a little more then

Very good info and pics BTW, much better then what I had

Rogue · Mar 10, 2010

You had pictures and did not share!

Whitewind · Mar 10, 2010

Great write up!!!

Note: After doing this make SURE you did not leave shavings around on you fuel system. Spray it down after drilling everything. (I know its common sense but lol)

TheSin · Mar 10, 2010

I documented it all in my thread

I didn't take pics of the during cause i had no idea if it was going to work I only had pics of the pump all in pieces. this is a much better write up

nystc23 · Mar 10, 2010

so if you are stock with stock set-up, this is not necessary? or do you need to make sure you clean that filter every X,XXX miles?

TheSin · Mar 10, 2010

I think stock you are fine, it's not a reusable line, you need to buy new ones everything time you want to clean that filter, so hopefully it won't need it. I think most of the debris in that filter is from messing with the fuel system, since it's in the return that would be after the injectors

nystc23 · Mar 10, 2010

ok, good to know :thumbup: thanks!

Rogue · Mar 10, 2010

Is the filter even needed?

TheSin · Mar 10, 2010

I questioned that when I cleared mine, but the return system is so OVER complex I didn't want to mess with it. If debris made it passed that point it could create major havoc and some of the path ways aren't so accessible. So I opted to put it back I guess it depends on how confident your lines will stay debris free, the filter is a pain to get to and you have to replace a line, but at least I know the parts I need, if past that you'd have to check the entire system and clear it out of each of the 3 different pathways.

Clipse3GT · Mar 10, 2010

I got rid of mine... no issues lol... I added a inline filter though.

Clipse3GT · Mar 15, 2010

Okay, I did more research. I think I came with a severe issue.

If you drill this hole out to 5/16" it will be way too large.

It will cause not enough pressure to be driverted to the hole that connects to the blue connector on the fuel assembly holder. So what does this mean? It means that blue connector causes a "swirling effect"/"venturi pump effect" which will not suck fuel the other side of the tank. Meaning you will run out of fuel 1/4th to 1/3" tank of fuel left. Scary on the highway.

The porting does not effect this effect. However, removing that restrictor does.

The fix is to get some aluminum rod. cut about .125" off drill a 5/65th" hole in the middle, then start filing away the sides to make it fit the hole. Luckily if you used a 5/16th earlier, it leaves a step, which now inturn you can insert the restrictor pill and press it in. Solves the issue and restores the venturi pump effect intank.

Kooldino · Aug 3, 2010

Might wanna update your first post with this.

Golden · Mar 15, 2010

I thought that aluminum and Ethanol don't mix well?

Clipse3GT · Mar 15, 2010

Hmm.... AN fittings are made of aluminum, fuel rail made of aluminum...

I am sure it is fine to use.

I run on 93 oct. Not too much ethanol either way...

TheSin · Mar 15, 2010

so I'm gonna just stay with the 5/65th hole I drilled to start with, gives me the same effect, good info thanks for the heads up.

boostin20 · Mar 15, 2010

sub'd

goofygrin · Mar 15, 2010

Straight Al = REALLY bad with E85.

Anodized (including clear anodization) Al is fine with E85.

Frankiago · Aug 2, 2010

Clipse3GT said:
fuel rail made of aluminum...

I am sure it is fine to use.

Stock fuel rail is aluminum, no? Clear anodized on the inside surfaces?

I'm working on my E85 conversion now, rounding up parts and pieces for a surge tank setup...

Clipse3GT · Mar 15, 2010

Then use steel/brass rod...

big boss · Aug 2, 2010

Would this happen with the Blaqops Fuel Pump kit?

Clipse3GT · Aug 2, 2010

IIRC, yes it still can happen with that kit.

IndyEvo · Aug 2, 2010

stock fuel rail is steel. aftermarket rails are aluminum.

Kooldino · Aug 3, 2010

Are you guys talking 80psi at idle or what?

Inner Control · Sep 6, 2010

make it a sticky guys..
did it to my car today after burning 4 walbro`s
same gasket completely shoved in that tiny needless filter...
did a small porting like "the sin"
need to change the tired walbro but AFR already steady at 11..5-12.5

kathleenp980 · Sep 6, 2010

Clipse3GT said:
There is a potential for having very high fuel pressure in the EVO X if the stock fuel system is modified.

The reason for this is the stock fuel pump assembly return line flaw...

I upgraded my fuel system with the following...

Upgraded fuel rail, injectors, fuel lines AN 6 feed and return, return line AN 4 to hard line, inline fuel filter, 1:1 fuel pressure regulator, walboro fuel pump.

What started to happen is a very high fuel pressure... of 80+ psi at the FPR.

STOCK: 38 PSI with VAC
STOCK: 45-50 PSI with NO VAC

My reading = 80 PSI (something was not right)

After getting to do the fuel pump assembly installing the new fuel pump and FPR I was still getting 80 psi...

After much searching (with help of theSIN) we figured out why...

1.) You need to take out the fuel pump assembly and all the goodies inside... there is multiple how to's refer to those for the steps.

1.) There is a restriction in the fuel return housing part. There is a 3 way connector. One hole has a pin hole (literally) in it. It has to be enlarged in order to accommodate more flow (larger lines, higher flowing fuel pump). Here is a after the enlargement picture.

Need a 5/16" drill bit & drill to enlarge it.

2.) The fuel return line has a FILTER!!! I know WTF is what I thought as well. It is miniature. Maybe like 4mm in size. It sits in the fuel return line assembly (you need to take off the fuel hose to see it or unclog it). If this filter gets clog it will cause your fuel pressure to sky rocket.

Here is the picture of the filter... It was clogged with this rubber gasket (not sure where it came from).

Also in the same connector there is a spring with valve in it. I believe it is a pressure relief valve. I opted to keep mine functional however. I did port the passage with a 5mm drill bit.

Pressure Relief Valve Apart

3.) I also ported 3 of the 4 passage with a 5mm drill bit to enhance flow.

TOP

SIDE

BOTTOM

Picture of Setup

Thanks you for the post picture

:yay:

mlomker · Sep 6, 2010

Clipse,

A bit off-topic but do you consider it safe to put the afpr on the firewall? I had someone tell me that since it is the hot-side of the motor that such a placement isn't considered safe (wouldn't pass tech at some tracks).

For that reason I was about to mount mine up front, on the driver's side radiator support. It's an awkward placement but seemed to comply.

WARNING / HOW TO: Fuel Line Return (High Pressure)

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