WARNING / HOW TO: Fuel Line Return (High Pressure)
Mar 9, 2010, 01:10 PM
#1
WARNING / HOW TO: Fuel Line Return (High Pressure)
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
Question:
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.
Answer:
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.
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
Question:
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.
Answer:
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.
Last edited by Clipse3GT; Mar 9, 2010 at 01:27 PM.
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Mar 9, 2010, 07:35 PM
#4
Based on the "evidence," you cannot conclude that any modification to the return line is necessary.
I am upgrading my fuel system shortly to accommodate E85 in this manner:
Completely stock fuel pump/tank
In-line filter
Surge tank
Walbro 255lph fuel pump
In-line filter
Stock fuel system from there up until a set of 1100cc injectors
The first in-line filter is mainly for the E85 conversion and to save the surge tank and Walbro from any "leftovers" the E85 frees up. The second in-line filter is for redundancy. I'll clean out and inspect both filters periodically to make sure nothing more than expected shows up while the system is getting used to E85.
clipse, thanks for the info on the stock return line's filter, I'll see what I can do with that when the time comes to connect the fuel rail's return line over to the surge tank.
Mar 9, 2010, 07:56 PM
#6
There's no way of telling if he would've just removed the clog and done no modification whether or not it would've COMPLETELY solved the high pressure issue.
Based on the "evidence," you cannot conclude that any modification to the return line is necessary.
I am upgrading my fuel system shortly to accommodate E85 in this manner:
Completely stock fuel pump/tank
In-line filter
Surge tank
Walbro 255lph fuel pump
In-line filter
Stock fuel system from there up until a set of 1100cc injectors
The first in-line filter is mainly for the E85 conversion and to save the surge tank and Walbro from any "leftovers" the E85 frees up. The second in-line filter is for redundancy. I'll clean out and inspect both filters periodically to make sure nothing more than expected shows up while the system is getting used to E85.
clipse, thanks for the info on the stock return line's filter, I'll see what I can do with that when the time comes to connect the fuel rail's return line over to the surge tank.
Based on the "evidence," you cannot conclude that any modification to the return line is necessary.
I am upgrading my fuel system shortly to accommodate E85 in this manner:
Completely stock fuel pump/tank
In-line filter
Surge tank
Walbro 255lph fuel pump
In-line filter
Stock fuel system from there up until a set of 1100cc injectors
The first in-line filter is mainly for the E85 conversion and to save the surge tank and Walbro from any "leftovers" the E85 frees up. The second in-line filter is for redundancy. I'll clean out and inspect both filters periodically to make sure nothing more than expected shows up while the system is getting used to E85.
clipse, thanks for the info on the stock return line's filter, I'll see what I can do with that when the time comes to connect the fuel rail's return line over to the surge tank.
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.
Answer:
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.
Mar 9, 2010, 08:01 PM
#7
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.
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Mar 9, 2010, 08:03 PM
#8
I don't think it hurts anything if you do these modifications. It is just peace of mind and gives you control over the fuel pressure better. Right now I can go from 20-90 psi pretty much.
I don't think people actually check their fuel pressure. I bet there might be a handful of EVO's that are running around 60+ psi without even knowing it.
I don't think people actually check their fuel pressure. I bet there might be a handful of EVO's that are running around 60+ psi without even knowing it.
Mar 9, 2010, 08:06 PM
#10
Yeah but really curious as to where that chunk of rubber came from...
Like you said, some might even be tuned with 60psi fuel pressure without even knowing it
I can just see it now... people purposely putting a restriction in the return line's filter as a ghetto way of raising fuel pressure and getting away with using smaller injectors...
Like you said, some might even be tuned with 60psi fuel pressure without even knowing it
I can just see it now... people purposely putting a restriction in the return line's filter as a ghetto way of raising fuel pressure and getting away with using smaller injectors...
Mar 9, 2010, 08:20 PM
#14
Yeah but really curious as to where that chunk of rubber came from...
Like you said, some might even be tuned with 60psi fuel pressure without even knowing it
I can just see it now... people purposely putting a restriction in the return line's filter as a ghetto way of raising fuel pressure and getting away with using smaller injectors...
Like you said, some might even be tuned with 60psi fuel pressure without even knowing it
I can just see it now... people purposely putting a restriction in the return line's filter as a ghetto way of raising fuel pressure and getting away with using smaller injectors...
However, with a restriction there. I noticed my pressure gauge was all over the place bouncing at back and forth +/- 5 PSI.
Mar 9, 2010, 08:24 PM
#15
Yeah but really curious as to where that chunk of rubber came from...
Like you said, some might even be tuned with 60psi fuel pressure without even knowing it
I can just see it now... people purposely putting a restriction in the return line's filter as a ghetto way of raising fuel pressure and getting away with using smaller injectors...
Like you said, some might even be tuned with 60psi fuel pressure without even knowing it
I can just see it now... people purposely putting a restriction in the return line's filter as a ghetto way of raising fuel pressure and getting away with using smaller injectors...
Dunno...
It's not from a rubber hose 100%. It looks almost like that sealing crap they put on the cover around the fuel pump assembly.