Fueling & Injection Fuel Pumps | Injectors | Rails | Regulators | Tanks

Fuel plumbing

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Old Feb 20, 2026 | 07:08 PM
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Default Fuel plumbing

Just want to make sure Im going down the right rabbit hole. Got a boost refernce FPR it has vacumme port and three fuel ports two marked in/out and one marked return. I am going to assume I come off my intake pump to filter (just filter one in one out) up to FPR "IN" and the other one marked "OUT" goes to feed side of fuel rail and the return goes back to the tank. Now th3 question is what do I do with my stock vacuumm regulated rails? Just plug in the feed rail and be done? I am thinking no. Ditch the stockers and go full money send on more aftermarket yeehaww or try and salvage the flex fuel rails I have from when I poached my flex fuel injectors because they dont have a return line just an inlet and cross over tube.
second question I have a set of aftermarket rails but they are tapped on 3 ends fir pipe thread and the 4th end is ready for a push fitting and lock screw but then in an awkward positiin I ha e two more push fittings for cross over tube but there is no way to clamp them down if i did use thwm and if i just run a flex line from one end to another i dont see any way to cap those holes easily anyway. There is a small hole that looks like ment for a gauge also butnit is not tapped just smooth.
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Old Feb 21, 2026 | 09:47 AM
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You don't want the regulator before the rails, it's a restriction that way. Run the fuel line directly to one rail, then a crossover to the other rail, then a return line from that rail to the regulator, cap off the fuel out side and run a line back to the tank from the return port.
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Old Feb 21, 2026 | 09:56 AM
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Originally Posted by LS1Formulation
You don't want the regulator before the rails, it's a restriction that way. Run the fuel line directly to one rail, then a crossover to the other rail, then a return line from that rail to the regulator, cap off the fuel out side and run a line back to the tank from the return port.
so pump,filter,rail, rail,fpr...plug second port on regulator and return back to tank. You got it toyota
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Old Feb 21, 2026 | 10:40 PM
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Originally Posted by BReal408
so pump,filter,rail, rail,fpr...plug second port on regulator and return back to tank. You got it toyota
You could also run pump, filter then into a Y block then into both rails and out the back into the regulator then return line to the tank.
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Old Feb 22, 2026 | 12:06 PM
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Either way we've described will work. Just always place the regulator after the rails.
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Old Feb 23, 2026 | 09:31 AM
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I have mine before rails with no issues
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