Fuel Pump

Remove and replace the mechanical fuel pump on the 390ci V8 engine, including fuel line disconnection and pushrod inspection.

Warnings

Tools required

Parts

• Mechanical fuel pump × 1 — Use OEM specification for 390ci V8
• Fuel pump mounting gasket × 1 — Use OEM specification
• Fuel pump pushrod (inspect and replace if worn) × 1 — Use OEM specification

Preparation

1. Ensure engine is completely cold to touch
2. Park vehicle on level surface and engage parking brake
3. Disconnect negative battery cable to eliminate ignition sources
4. Place fire extinguisher within immediate reach of work area
5. Ensure work area is well-ventilated with no ignition sources present
6. Position drain pan under fuel pump area to catch fuel spillage
7. Have multiple shop rags ready to contain fuel spills

Procedure

1. 1

   Relieve residual fuel pressure
   Remove the gas cap to relieve any vapor pressure in the fuel tank. On the 390ci V8 mechanical pump system, residual pressure is minimal but fuel will still drain from lines when disconnected. Ensure drain pan is positioned directly under the fuel pump on the right side of the engine block.
   ⚠Fuel will drain from lines when disconnected. Keep rags ready to absorb spillage.
2. 2

   Disconnect fuel inlet line
   Using a flare nut wrench, carefully loosen the fuel inlet line fitting at the fuel pump (line from fuel tank). Hold the pump inlet fitting with a backup wrench to prevent twisting the pump body. Once loose, have a rag ready and remove the line completely. Fuel will drain; catch it in the drain pan. Plug the line with a rubber cap or wrap with clean rag to prevent dirt entry.
   ⚠️Fuel will spill when line is disconnected. Keep face and ignition sources away from connection point.
3. 3

   Disconnect fuel outlet line
   Using a flare nut wrench, loosen the fuel outlet line fitting at the fuel pump (line to carburetor). Hold the pump outlet fitting with a backup wrench. Remove the line and plug or cover the end with a clean rag. The carburetor fuel bowl may drain back through this line.
   ⚠Additional fuel may drain from carburetor. Position drain pan accordingly.
4. 4

   Remove fuel pump mounting bolts
   Locate the two fuel pump mounting bolts securing the pump to the engine block on the right side. Using a 1/2" or 9/16" socket (verify size on your specific pump), remove both mounting bolts. Support the fuel pump with one hand as you remove the second bolt to prevent it from falling.
5. 5

   Remove fuel pump and pushrod
   Carefully pull the fuel pump away from the engine block. The fuel pump actuating pushrod may come out with the pump, fall into the block, or remain in the block bore. If it doesn't come out with the pump, use a magnetic pickup tool or carefully extract it from the pushrod bore in the block. Inspect the pushrod for wear, scoring, or uneven wear patterns on both ends.
   ⚠Do not drop pushrod into engine. If pushrod falls into block, it must be retrieved before continuing or engine damage will occur.
6. 6

   Clean mounting surface
   Remove old gasket material from the engine block mounting surface using a gasket scraper. Be careful not to gouge the aluminum or cast iron surface. Clean thoroughly with a wire brush and shop rag. Inspect the mounting surface for cracks or damage. Ensure pushrod bore is clean and free of debris.
7. 7

   Inspect and install pushrod
   Inspect the fuel pump pushrod for wear on both ends (the eccentric-contact end and pump-contact end). Replace if any wear, scoring, or uneven patterns are visible. Coat pushrod lightly with clean engine oil. Insert pushrod into the block bore, ensuring it seats properly against the eccentric on the camshaft. Verify pushrod moves in and out freely when rotated by hand (rotate crankshaft slightly if needed to feel movement).
   ⚠Pushrod must move freely and seat against camshaft eccentric. If binding occurs, investigate cause before proceeding.
8. 8

   Position new gasket and fuel pump
   Place the new fuel pump gasket on the engine block mounting surface (dry installation - no gasket sealer needed unless specified by pump manufacturer). Position the new fuel pump against the gasket, aligning the mounting bolt holes. The pump actuating arm must engage with the pushrod - you may need to rotate the engine slightly to position the eccentric for easier installation. Apply light pressure to compress the pump spring while aligning bolt holes.
   ℹ️Pump spring tension will push pump away from block. You may need to rotate crankshaft to position eccentric at low point for easier installation.
9. 9

   Install fuel pump mounting bolts
   Start both mounting bolts by hand to ensure proper thread engagement. Tighten bolts evenly in a crossing pattern to prevent cocking the pump. Use a torque wrench to tighten bolts to proper specification (typically 18-22 ft-lbs for AMC 390ci applications, but verify with pump manufacturer specifications as no database torque value is available). Do not overtighten as this can crack the pump body or distort the mounting flange.
   ⚠Overtightening can crack pump housing. Tighten evenly and to specification only.
10. 10

    Reconnect fuel outlet line
    Remove the plug or rag from the fuel outlet line (to carburetor). Thread the fitting into the fuel pump outlet by hand first to prevent cross-threading. Use flare nut wrench to tighten securely while holding pump fitting with backup wrench. Tighten until snug - do not overtighten flare fittings.
11. 11

    Reconnect fuel inlet line
    Remove the plug or rag from the fuel inlet line (from tank). Thread the fitting into the fuel pump inlet by hand first. Use flare nut wrench to tighten securely while holding pump fitting with backup wrench. Tighten until snug but do not overtighten.
12. 12

    Reconnect battery and prime fuel system
    Reconnect the negative battery cable. Before starting engine, manually prime the fuel pump by rotating the engine over several times with the starter in short bursts, or by manually operating the pump priming lever if equipped. Check all connections for fuel leaks during priming. Wipe any spilled fuel and allow vapors to dissipate.
    ⚠️Inspect all fuel connections for leaks before starting engine. Any leak must be corrected immediately.

Reassembly

1. Ensure all fuel line connections are tight and leak-free
2. Verify no tools or rags are left in engine compartment
3. Double-check that fuel pump mounting bolts are properly torqued
4. Clean up any spilled fuel and ensure work area is well-ventilated before starting engine

Verification

• Start engine and let idle - observe fuel pump for leaks at all connections and mounting gasket
• Check for fuel leaks at inlet and outlet line connections while engine runs
• Verify fuel pressure at carburetor inlet (should see fuel flowing when throttle is pumped)
• Listen for unusual noises from fuel pump - should operate quietly without knocking
• Test drive vehicle to verify proper fuel delivery under load and acceleration
• Re-check all connections for leaks after test drive when engine is warm
• Monitor for fuel odors in following days - any fuel smell indicates a leak requiring immediate attention

More procedures for this vehicle