K-Swap Fuel System: Center-Feed Fuel Rail and Tucked Return Fuel Lines (Civic EG/EK, Integra DC2)
- Fuel vapour is explosive: no smoking, sparks or open flames, and keep a fire extinguisher nearby.
- Wear eye protection; fuel can spray from a line that is still under pressure.
- Disconnect the battery before opening fuel lines.
- Never block the fuel tank vent line.
Introduction
K-series engines come with a returnless fuel system, with the pressure regulator in the fuel tank and a single line to the rail. A 1992-2000 Civic or 1994-2001 Integra has a return-style system, so a K-swap needs a regulator in the engine bay to control pressure and send excess fuel back to the tank. Hybrid Racing's tucked kit runs a feed line from the center port of an aftermarket rail down between runners 2 and 3, through an inline filter and along the transmission to a regulator mounted below the brake booster, then ties into the chassis feed and return hard lines. This guide covers swapping the rail, routing the lines and setting pressure. Adapted from a community writeup by Hybrid Racing on guides.hybrid-racing.com (https://guides.hybrid-racing.com/Guide/Hybrid+Racing+Tucked+K-Swap+Fuel+Line+Kit/177).
Procedure
14 steps-
Step 1: Identify the lines and ports
Lay out the rail, filter, regulator and lines. In the Hybrid Racing kit, line A runs from the rail's center port to the filter, line B from the filter to regulator port 2, line C from regulator port 1 to the chassis feed line, and line D from regulator port 3 (return) to the chassis return line.
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Step 2: Relieve fuel pressure and disconnect the battery
Work outdoors or in a well-ventilated area with no ignition sources, wear eye protection and keep a fire extinguisher within reach. Disconnect the battery and relieve fuel pressure using the procedure in the factory service manual for your chassis before opening or cutting any line. Keep rags around any fitting you open, because lines can still hold pressure.
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Step 3: Remove the injector cover and harness
Remove the two 10 mm cap nuts and pull off the injector cover (it is held by rubber grommets). Unplug the four injectors, unbolt the injector harness ground from the manifold and unclip the injector harness from the rail.
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Step 4: Remove the stock rail
Remove the two 12 mm nuts and pull the rail off the manifold; the injectors usually come out with it. Pull the retaining clips and remove the injectors over a drain pan, as fuel will run out of the rail.
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Step 5: Set up the new rail's ports
Fit the feed fitting your line kit needs to the center port; the Hybrid Racing line kit does not include the rail adapter. Plug unused ports, or fit a gauge in the gauge port, using fuel-safe sealant on pipe threads.
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Step 6: Fit the injectors and rail
Lightly oil each injector O-ring, press the injectors into the new rail, then line them up with the manifold bores and press the rail home. Refit and tighten the two 12 mm nuts. Reconnect the injectors in the correct order (INJ1 at the timing-chain end).
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Step 7: Route the feed line from the rail
Connect line A to the rail's center port and route it down between the intake runners and along the side of the head. Fit the inline filter on the end of line A.
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Step 8: Route the line to the regulator
Connect line B to the filter and turn its 90-degree fitting so the line heads toward the driver-side (left-hand) shock tower. It may run above or below the shifter cables as long as it is clear of heat and moving parts.
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Step 9: Mount the regulator
Pick a regulator position where lines C and D will reach the chassis hard lines; Hybrid Racing's kit is designed for a regulator mounted below the brake booster. Mount it solidly.
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Step 10: Cut the chassis hard lines
Cut the factory feed and return hard lines to length with a tube cutter and file off any burrs. The feed line is the larger tube that originally went to the factory fuel filter on the firewall; the return is smaller and shorter.
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Step 11: Connect feed and return
Connect line C to the chassis feed line and line D to the chassis return line.
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Step 12: Leave the tank vent line open
The third line in this area is the fuel tank vent (charcoal canister) line. Never cap or plug it; it must be able to vent at all times. A temporary cap to keep dirt out during the job must come off before the car runs.
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Step 13: Fit the gauge and leak-check
Install a fuel pressure gauge and check every fitting is tight. Reconnect the battery and cycle the key several times to build pressure; a car that has sat may need several cycles. Inspect every joint for leaks before starting. Then start the engine and inspect every joint again at running pressure. Shut off immediately if you see a drip or smell fuel.
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Step 14: Set fuel pressure
With no leaks, adjust the regulator. Hybrid Racing specifies 52 psi for its kit; confirm the base pressure with whoever tunes the car.
- Hybrid Racing describes its lines as E85-compatible; check the filter and regulator are also rated for the fuel you run.
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