Fuel Line Layout for LS Swap with LM4

[19SIKtySix]

I know this is the best place to come for answers so:

I just picked up the heartbeat of my LS swap, but there's so much to learn about these swaps.

I found out my particular engine has a returnless fuel rail so I'm trying to map out my fuel layout. I was told the FPR is located on the rail, so all that is needed is a filter outside the tank. Is this correct?

I plan to move the tank to the rear, anybody have experience with the FiTech single pump retrofit kit?

[MIKESAD50]

What year is the LS out of?
Generally cars that have "returnless" systems have the regulator in the pump assemblies in the tank, or near the rear of the vehicle. on part of the fuel filter.

Returnless fuel rails have just one connection.

I used a Aeromotive Phantom in tank pump and used Holley LS sway Fuel regulator/filter assembly mounted on frame rail then ran a return line back to tank.

Youu can use a corvette style filter which has built in regulator.
Have never used the FI tech set ups

[mongocanfly]

there is no regulator on the fuel rail of a returnless system,
if you use a intank pump with a built in regulator you can use just a filter inline..
on my last one I used a external walbro 255 with the vette filter/reg...and I works fine
im thinking of using intank pump on my next one...but may go external as well

[19SIKtySix]

I'm trying to sort everything out as I'm going over this motor. With this being my 1st time dealing with a swap, there's a bunch of info to sort thru.

So regarding the LM4s, there were 3 years and it varied between return style and returnless depending on the vehicle year.

So when looking over the fuel rails, there are 2 lines coming off the driver side fuel rail. I was told it was a returnless system and all that is needed would be a filter outside the tank.

I ordered a boyd's welding tank with in-tank pump but still unsure what I need to have for my setup. I purchased a CPP fuel line kit with the filter/regulator combo but how would I plumb the fuel lines?

Any help is appreciated.

[mongocanfly]

If you have 2 lines on the rail then it IS a return rail system...if you got the boyds intake pump I think the reg will be in the tank and all youll need is a inline filter...not a inline reg...I capped off my return rail with a pushlok to taper fitting with a taper cap on that...dont use rubber caps or the like...thats still high pressure....
Not sure what all you got with the cpp kit but all you should need is one fuel line from intake pump to the fuel rail...with a inline filter somewhere along the way...put it where it'll be easy to get to ...cap off the return side of the rail like I stated above...you don't need the filter/reg...

[ls1nova71]

Originally Posted by 19SIKtySix

I'm trying to sort everything out as I'm going over this motor. With this being my 1st time dealing with a swap, there's a bunch of info to sort thru.

So regarding the LM4s, there were 3 years and it varied between return style and returnless depending on the vehicle year.

So when looking over the fuel rails, there are 2 lines coming off the driver side fuel rail. I was told it was a returnless system and all that is needed would be a filter outside the tank.

I ordered a boyd's welding tank with in-tank pump but still unsure what I need to have for my setup. I purchased a CPP fuel line kit with the filter/regulator combo but how would I plumb the fuel lines?

Any help is appreciated.

I don't know where you are getting your info, but if you have 2 lines coming off the rail, then it is a return style, not a returnless. It should have a regulator on the rail, with a vacuum hose attached to it. If that is the case, then just run a feed and return line from the tank to the engine with a regular filter in the feed line, you don't need the Corvette filter/regulator.

[mongocanfly]

/\ correct/\ I pulled up boyds...if you got the 340 in tank pump you'll need to use the return rail..

[19SIKtySix]

Yes, I tried to figure on a cheaper tank and retrofit an efi, but it only saved me like $150. Then Boyd's posted a sale this past weekend and I ended up saving like $60 so I went for it, I didn't want to cut corners on a tank.



I snapped a pic last night, so am I correct to assume the top line is the return and the bottom line is the input? Being that the top line tees off after the regulator on the rail.

The fuel line kit I purchased from CPP includes 25ft of hose, fittings with (2) 45 deg and filter/reg combo. Would it cause a problem to run (2) regulators on my fuel system? The 1st being the one located on the rail and the 2nd being the combo unit just outside the tank?



Thanks for the help guys, it's really appreciated!

Originally Posted by mongocanfly

/\ correct/\ I pulled up boyds...if you got the 340 in tank pump you'll need to use the return rail..

[mongocanfly]

It's not a problem to use the vett filter/reg that you got with the kit....but you'll need to cap off the return rail...if you do be sure to use -an fittings...
If you use the reg on the rail youll need to run that line back to the tank and not use the vett stuff...
I don't think you can run both regs...but I'm not sure..
You could do it either way...
And your system IS a return type system
And the top line is supply....bottom is return...
Here's a pic of mine...yellow arrow pointing at capped off return...

[19SIKtySix]

I have one more question about my swap, from looking around the web I think this is the vacuum connection but can somebody confirm?

[ls1nova71]

That is for the power brake booster if that's what you're asking. As for the 2 regulators thing, I personally wouldn't do it. Those regulators are known for leaking and will cause driveability problems when they do. Having the return blocked off will negate it so you may or may not know if its leaking, and leaking fuel on a hot engine is never a good idea. I would just run a return line, but if you're dead set on using the Corvette filter, just get a return less rail and do it the right way. They're all over the salvage yards for cheap. Also, I dont know what brand of filter CPP sells with their kit, but if it isnt AC Delco or Wix, you could have problems, cheap ones are known to be bad right out of the box.

[mongocanfly]

"( if you're dead set on using the Corvette filter, just get a return less rail and do it the right way. They're all over the salvage yards for cheap.)"

Stuff like this is what I had no clue about when I built mine all these yrs ago....at the time all i had to go on is what people were telling me.....

[19SIKtySix]

I'm just trying to sort out all the connections that need to be made to complete the swap. I only have a few disconnected plugs and hoses, so I'm trying to verify exactly what goes where.

Yes, I'd rather not use (2) regs, so I can avoid any issues. Thanks to Mongo, I'll just cap off the factory return rail. I'll wait and see if there's a part reference with my CPP order.

I'll go the route that causes the least amount of headache. My only concern about buying rails from a junkyard is making sure I purchase everything that's needed.

I feel there's so many little items that need to figured out with this swap and with those little changes, it could affect something else. So my goal is to do as much research as possible.

Originally Posted by ls1nova71

That is for the power brake booster if that's what you're asking. As for the 2 regulators thing, I personally wouldn't do it. Those regulators are known for leaking and will cause driveability problems when they do. Having the return blocked off will negate it so you may or may not know if its leaking, and leaking fuel on a hot engine is never a good idea. I would just run a return line, but if you're dead set on using the Corvette filter, just get a return less rail and do it the right way. They're all over the salvage yards for cheap. Also, I dont know what brand of filter CPP sells with their kit, but if it isnt AC Delco or Wix, you could have problems, cheap ones are known to be bad right out of the box.