Fuel Line Replacement – 2.5L NA

Overview

This procedure replaces the fuel delivery and return lines on the Porsche 944 (2.5L NA engine, 1985.5–1988 models) to eliminate the risk of fuel leaks and potential fires caused by aged, brittle lines. The process involves accessing the fuel lines through the front wheel well, disconnecting them at the fuel rail, and installing new high-pressure hoses, typically using cutting ring fittings. This guide is tailored for DIY enthusiasts with mechanical experience, ensuring safe and accurate replacement specific to the “LATE” configuration (1985.5–1988 models).

(This guide does not currently include the replacement of the jumper line (Fuel Line – Rail to Diaphragm Damper – 94411041303). Watch this video for more information.)

Special Note on Fuel Line Kits: Different fuel line replacement kits may require slightly different installation methods, particularly with regard to the types of fittings and connections used. For example, some kits use compression fittings for both the feed and return lines, while others may use clamps for the return line. Modern PTFE (Teflon) lines are also an option for enhanced durability and performance, especially for high-performance applications. Always refer to the instructions provided with your chosen fuel line kit for specific installation details.

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Tools Required

• Flathead screwdriver
• 16mm (5/8 inch) open-end wrench (Metric set)
• 19mm (3/4 inch) open-end wrench (Metric set)
• 24mm (15/16 inch) open-end wrench
• 10mm (3/8 inch) socket and ratchet
• 8mm (5/16 inch) Allen key
• Miniature pipe cutter or sharp blade
• Gloves (fuel-resistant)
• Aluminum foil (for covering fuel ports in fuel rail)

Parts Required

• Fuel Lines Kit – 944store.com
• Black heat shield sleeve for fuel lines
• Fuel pressure regulator o-ring (same as injector o-ring) – 944 1109 0101

Step-by-Step Procedure

Step 1: Prepare the Vehicle

1. Park the vehicle on a flat surface and engage the parking brake.
2. Disconnect the negative battery cable to prevent electrical issues during the procedure.
3. Jack up the front right side of the vehicle, securing it with jack stands at the longitudinal member. Remove the front right wheel to access the wheel well.

Step 2: Remove the Wheel Well Lining

4. Locate the six fasteners securing the wheel well lining: two plastic nuts at the top (near the fender edge), one behind the strut, one at the lower edge, and two sheet metal screws at the front.

• Use a 10mm (3/8 inch) socket for the sheet metal screws and a flathead screwdriver for the plastic nuts. The lower screw may require an 8mm (5/16 inch) socket if different.

5. Carefully pull the lining away, starting at the rear seam and sliding it past the strut, to expose the fuel lines and their holders.

Step 3: Disconnect the Fuel Lines at the Fuel Rail

Caution: Ensure the engine has been sitting for a number of hours so that the fuel system is depressurised and the exhaust headers are cool to avoid the risk of fire.

6. Open the hood and locate the fuel rail at the top of the engine.
7. At the rear of the fuel rail, use a flathead screwdriver to loosen the clamp on the return line connected to the fuel pressure regulator. Slide the clamp back to free the hose.
8. At the front of the fuel rail, use a 19mm (3/4 inch) open-end wrench and a 24mm (15/16 inch) open-end wrench to loosen the delivery line fitting connected to the fuel pressure damper. Place a rag or container to catch any fuel spray.
9. Cover the open ends of the fuel regulator and damper with aluminum foil and secure with tape to prevent contamination.

Step 4: Remove the Old Fuel Lines

10. In the wheel well, locate the two plastic holders securing the fuel lines. Use an 8mm (5/16 inch) Allen key to carefully loosen the screws, applying gentle pressure to avoid stripping.
11. Release the fuel lines from the holders and rubber grommets. Apply petroleum jelly to the grommets to ease removal and protect them.
12. Use a miniature pipe cutter to cut the delivery line as low as possible in the wheel well, rotating and tightening the cutter gradually to avoid burrs. Repeat for the return line.
13. Carefully maneuver the old lines out through the wheel well, navigating tight spaces around the brake lines.

Step 5: Install the New Fuel Lines

14. Insert the new delivery line from the bottom of the wheel well, routing it through the same path as the old line. Ensure it sits in the rubber grommets of the holders.
15. Follow the specific instructions provided with your fuel line kit for assembling the fittings. Typically, this involves using compression fittings for the high-pressure feed line and either compression fittings or high-quality hose with clamps for the return line, depending on the kit.
16. For standard kits using cutting ring fittings:

• Measure 7mm from the end of the delivery line and cut cleanly to remove any flared portion.

• Slide the nut onto the line, followed by the cutting ring (thicker side toward the fitting). Insert the line into the fitting and tighten to 20 Nm (15 ft-lbs).

17. Repeat for the return line, measuring 6mm for the cutting ring fitting due to its smaller size, and tighten to 20 Nm (15 ft-lbs).
18. Connect the delivery line to the fuel rail via the fuel pressure damper. Connect the return line to the fuel rail via the fuel pressure regulator with the clamp.
19. Depending on your kit, it may be required to flip your regulator around, and this is done by simply removing the bolts, gently pulling it out of the rail, inspecting the seal (o-ring) to ensure is intact (installing a new one, if needed), and installing it with the vacuum tube side pointed towards the front of the car.
20. Secure the lines in the wheel well holders, ensuring they are fully seated in the rubber grommets, and tighten the holder screws with an 8mm (5/16 inch) Allen key to 5 Nm (4 ft-lbs).

Step 6: Reassemble and Test

21. Reinstall the wheel well lining, securing the six fasteners (plastic nuts and sheet metal screws) with a 10mm (3/8 inch) socket or flathead screwdriver to 10 Nm (7 ft-lbs). Ensure large washers are used under plastic nuts to prevent tearing.
22. Reinstall the front right wheel, applying a thin layer of ceramic paste to the hub (avoid copper paste on aluminum). Hand-tighten the lug nuts in a star pattern.
23. Lower the vehicle from the jack stands and tighten the lug nuts to 130 Nm (96 ft-lbs) in a star pattern.
24. Reconnect the battery.
25. Test the fuel system by turning the ignition to the “on” position (do not start the engine).
26. Use a fuel relay jumper to activate the fuel pump.
27. Listen for the fuel pump and feel the hoses for flow. Check for leaks at all connection points in the wheel well and at the fuel rail.
28. Verify that the lines are routed away from heat sources and sharp edges.

Post Procedure Checklist

• Check for fuel leaks at all connections in the wheel well and fuel rail.
• Verify that the fuel pump primes when the ignition is turned on.
• Ensure the new lines are secured in holders and routed away from heat sources and sharp edges.
• Confirm the wheel well lining and wheel are securely reinstalled.
• Inspect the fuel rail seal for integrity; replace if damaged.

Sources

• Pelican Parts
• Porsche 944 Workshop Manuals
• YouTube
• Lindsey Racing Tech Garage
• Rennbay Installation Videos