I need to plumb in a fuel return line on the RAV4. The OEM config is with a regulator in the tank, so the return is all inside the existing tank. The new motor has an external regulator at the end of the rail. I need to replace the fuel pump with a BIG one, remove the internal regulator and add an existing fuel return line. I'd rather not have to deal with hard lines, as bending them and getting them all to fit in the existing channel will be tough. I'm thinking of running some tough hose back to the tank, and some kind of bulkhead type fitting at the top of the tank, then drop it down inside the tank with the rest of the stuff. The tank is typical late model Toyota with the pump attached to a plate that bolts on the top.
So, what kind of bulkhead fitting do I need? Any other suggestions? When I converted the RN Truck to EFI, I kinda just used the vent line as the fuel return, and everything has work out fine with that. There is a vent line running up to the front. Don't know if I want to do that again or not. I'm putting a walbro 255 pump in the tank. I'm open to suggestions.
I've just drilled a hole and stuck an AN bulkhead fitting on my Dart's tank.
A regular beaded push-on fitting (used with a hose clamp) will work, I think that's how all factory EFI'd cars with fuel return lines are set up. A soft return line should be safe as long as it's well-protected - as in definitely not the lowest point on the frame.
There is kind of a cage over the existing fuel lines. It would be pretty hard to run the new line elsewhere. Maybe I could use the existing vapor hard line as the return line and plumb in a new soft vent line, change the vapor line connection to a bulkhead fitting, change the vapor connection to the new soft line? Still, I would rather not run gas lines through the cabin if I don't have to.
Modify the canister to bypass the regulator. If you google the "spoolboy mod" for Neon fuel pumps, it should give you a pretty good basic rundown of modifying a pump module.
Could use stock feed line to run to the rail. Attach an external regulator AFTER the rail (I see you already have this configuration), and run return line from regulator back to the pump module.
You can just run AN lines (-6 should probably work). They make nice aluminum brackets that will affix the line to a "frame rail" of your car, or you can use those rubber-coated metal jobs. Either will work fine. I've used the aluminum ones as a say to run AN pressure/return lines, and it always provides for a clean look. I would at the very least make sure you use braided line just for the sake of puncture resistance.
Alternatively, you can use the Ni-Copp hard lines. They're A LOT easier to work with vs. traditional hard line. You can actually bend it by hand.
I was going to just remove the existing in-tank regulator altogether when I replace the fuel pump.
Here's the stock setup:
You can see the stock FPR just down stream of the pump. My plan is to cut the pipe coming off that regulator and plumb the new pump directly to that pipe stub.
How is the factory system routed? Are you sure there's only one port in the tank, stock? On the non-return system I'm familiar with (NB Miata), the pump is in the tank, pumps the fuel out of the tank, through the filter, then it splits with one branch going to the fuel rail, the other going back to the tank and to the in-tank regulator. IOW, the "non-return" system here actually has a return, it's just that it only goes a couple feet out of the tank, instead of going all the way up to the engine bay. I think the reason they do it this way is that In order to build a system with only one port on the tank, you either have to put the fuel filter inside the tank or accept that the regulator will be unable to compensate for a fuel filter that slowly increases in resistance as it clogs.
How large is the existing vapor line? If it's significantly smaller than the fuel delivery line, then using it as the return line with an up-rated pump poses the risk of it being too large of a restriction and the regulator being unable to properly regulate the rail.
Have you considered getting a second factory fuel delivery hard line from a junkyard to use as your return line? It's pre-bent to the right shape, which solves that problem at least.
You can see in the pic how it is set up. Pump to FPR in the tank, FPR dumps excess fuel inside the tank, regulated line exits the tank. Fuel filter is mounted in the engine compartment on the wheel well, then to the dead end fuel rail (3SFE). No compensation for clogged fuel filter. Actually, I have only had one Toyota EFI system ever clog a fuel filter, and that was a 92 RN Truck very abused with a quarter million miles. Original filter, I'm sure, but the RN system has a return line. I have a new filter to put in this RAV. It, too, has a quarter million miles on it. The vapor line on the RAV is the same line size/material as the supply line.
A factory line would be nice, but pulling that from a vehicle at a junk yard would be a major job. I'm thinking either some braided line or work some generic hard line down the tunnel that shields the other 2 lines.
Codrus hit the nail on the head. Call Inline Tube or Classic Tube. They will have the CNC bending files to bend you a fuel line and you can even specify it in whatever diameter you need; for instance if the stock supply line is 5/16" (or metric equivalent) you can have them make it in 1/4" for the return. There is no problem using the full size return, its just easier to make subtle bends in smaller tubing.
They can also do factory beads on the end or 45 degree flare (brake line type) or 37 degree for AN fittings. I have sent both companies very detailed drawings and specs for custom brake and fuel lines and they have always come through flawlessly.
Another option would be to use a "soft" line like some American cars use. Its a black plastic tube that bends nicely with a little heat from a heat gun, but it does require special fittings.
Summit Racing and Jegs sell aluminum fuel line that bends very easily, or you could buy one of their kits with braided line (although soft lines fail more frequently)
I wouldn't trust anything short of a hard line or SS braid AN.
I think shipping like 8' of pre-bent tubing undamaged might be a bit expensive. I've worked with the JEGS coils of tubing. The Locost has that in it. Might even have some left over. Didn't think about the GM Plastic stuff. That might work. I'll still have to figure the ends out, but I wouldn't have to worry about it destroying everything around it like with stainless braided. I could use the plastic as the vent and the existing hard line as the return.
Dr. Hess wrote:
I think shipping like 8' of pre-bent tubing undamaged might be a bit expensive.
Its not bad. They ship it bent in half with a broad arc. The box isn't as big as you think.
Get another fuel line from a donor and wire tie it right next to the original.
Running a soft line under a vehicle (even braided) is sketchy, it must be up tight and in the groove and in no position to get smashed or otherwise run aground.
For the entrance to the tank, its best to go through the module and route the return fuel into the module canister.
If you route return fuel elsewhere in the tank the pump may pump the canister dry at lower tank levels. Especially during spirited maneuvers.
Another way to deal with this is with a swirl tank.
I could run brake line, right? I mean, it's just a vent if I use the existing vent as the actual return.
Too small may restrict flow and not allow the regulator to fully limit fuel pressure
I think the better stocked preflared racks have 3/8 available for fuel, trans cooler, PS, etc. I know they make polyarmor that big.
I would use the existing vent line, which is the same size as the supply line, as the new return line, and maybe a brake line as the new vent line going up to the engine bay.
Most vent ines I have seen are smaller, if it is the same size as the feed I would not hesitate to use it. It will need a re-direct at the tank end though.
What about capping the regulator at the rail and using a corvette style filter regulator combo and set it somewhere close to the pump? Less routing youd have to worry about. Just tossing out a random idea
chiodos wrote:
What about capping the regulator at the rail and using a corvette style filter regulator combo and set it somewhere close to the pump? Less routing youd have to worry about. Just tossing out a random idea
That's a good point. The corvette fuel pump includes the regulator for a short run back to the tank.
Not sure what you're putting in, but will the stock pump/reg supply enough to the new engine? If so, just remove the fuel rail regulator and cap it off. Its not the most accurate way, but it is effective.
You can get all kinds of bulkhead fittings for a return line. Try to install the return in the least likely place to see liquid fuel. For some applications its not a big deal, but if you have a lot of flow coming back the bypass/return and a wave of fuel smacks into the return it can cause a momentary pressure rise. That is usually a problem when people oversize the fuel pump and there is a large amount of flow coming back the return. I plumbed an A1000 pump in a 51 Merc (way overkill) and I had to end up putting the return fitting in the filler neck of the tank. Every where else I put it, it caused problems. There was enough flow coming back to the tank that the resistance of trying to push it into liquid fuel in the tank made the regulator confused.
The new motor is a 4th gen 3SGTE. The regulator is on the end of the rail and connected to vacuum/boost to adjust pressure accordingly. The original fuel pump supplied fuel for about 1/3rd the HP and "I read on teh intr4w3bz, y0" that it is insufficient for the 300 HP motor. Certainly, with the regulator down in the tank and no vacuum line to it, it would not work with the factory ECU that I am running.
The difference between idle and ZOMG fuel requirements are so large that there is a fuel pump resistor in the fuel pump circuit to reduce the output when demand is low, then it is bypassed by a relay when in ZOMG mode.
Same story with my RX8. I am using the stock fuel line as my return line. My new hgh pressure line is welded schedule 40 aluminum pipe, 0.364" ID, 0.090" wall with fittings welded to the ends. Way overkill... I'm using an AN bulkhead fitting to get the new pressure line out of the tank.
I've used this method in a few places as well. Take your pick of stainless or aluminium tube.
Monkeywrench racing has a kit to do mkiii mr2s, check out their site.
OK, the evap line is smaller and runs to the back top of the tank. There is also a line called the fuel return breather tube. It runs from the filler neck just below the gas cap down to the top of the cassette thing that holds the fuel pump. There is a rubber section close to the fuel pump side, it is metal the rest of the way up to the gas cap.
What I'm thinking here is to T into that line at the rubber part next to the tank and run a hard line to the engine bay. As there is no restriction on either end of the line, the return should dump back into the tank, or at very worst case, go against gravity up to the top of the filler neck, splash into the filler neck and come back into the tank. The gas cap is one of the typical modern screw-in kind. The hard line size is the same as the fuel supply size. If I made a Y connector and pointed the return towards the tank, the uphill flow would be even more minimized.
What do you guys think?
Dr. Hess wrote:
The new motor is a 4th gen 3SGTE.
This is what i was hoping you were putting in, please make a build thread for it!
