🔧 Installing a Fuel Pump & Sending Unit in an ’84 Monte Carlo LS Swap

When upgrading to an LS swap, fuel delivery is one of the most critical parts of the build. On my 1984 Chevy Monte Carlo, I’m replacing the entire sending unit with an upgraded in-tank fuel pump to support the LS engine’s higher fuel pressure requirements. This ensures reliable fuel supply, proper return line function, and long-term performance.

🛠️ Step-by-Step Overview
1. Safety First – Disconnect the battery and safely relieve any remaining fuel pressure. Work in a well-ventilated area and keep a fire extinguisher nearby.
2. Drop the Tank – Support the gas tank with a jack and remove the retaining straps. Carefully lower it enough to disconnect the filler neck and any vent hoses.
3. Remove Old Sending Unit – Once the tank is out, clean around the lock ring to prevent debris from falling in. Use a brass punch or fuel pump lock ring tool to turn and release the old unit.
4. Install New Sending Unit with Pump – Place the new sending unit (with integrated high-pressure fuel pump) into the tank. Make sure the pump sock/strainer is properly seated. Secure the lock ring tightly.
5. Update Fuel Lines – Run high-pressure-rated fuel lines (return and supply) from the pump to the engine bay. Ensure proper clamps and AN fittings if upgrading to EFI-spec lines.
6. Reinstall Tank – Lift the tank back into place, reconnect filler neck, vent hoses, and electrical connectors. Bolt the straps back securely.
7. Wire the Fuel Pump – Use a proper relay and fuse to wire the pump to your LS swap harness, ensuring it primes when the ignition is switched on.
8. Test & Verify – Reconnect the battery, cycle the key to pressurize the system, and check for leaks. Verify fuel pressure matches LS requirements (usually ~58 PSI).

✅ Results

With the new sending unit and in-tank pump, the LS engine will have consistent fuel pressure and flow—no starvation issues, no hiccups, just smooth power delivery. This is a crucial step in making the LS swap reliable and ready for the road or track.

🔑 Key Notes
• Always use an EFI-rated fuel pump and lines for LS swaps.
• Replace the fuel filter when doing the pump swap.
• Double-check wiring polarity—reversed pump wiring can burn out the unit instantly.
• Plan for a fuel return system unless you’re using a returnless setup with a regulator.

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