Mechanical Fuel Pump Service

Remove, inspect, and replace the mechanical fuel pump on a 1966 Chevrolet Corvette 327ci V8, including gasket replacement and fuel line service.

Warnings

Tools required

Parts

• Mechanical fuel pump × 1 — AC Delco 40902 or equivalent
• Fuel pump mounting gasket × 1 — Use OEM specification
• Fuel pump pushrod × 1 — Inspect and replace if worn
• Fuel line crush washers or gaskets × 2 — Use OEM specification

Preparation

1. Ensure engine is completely cold to touch
2. Position vehicle on level ground and engage parking brake
3. Disconnect negative battery cable to eliminate ignition sources
4. Place fuel-safe container and absorbent rags under fuel pump area
5. Verify fire extinguisher is accessible
6. Remove air cleaner assembly if it obstructs access to fuel pump
7. Relieve fuel system pressure by loosening fuel tank cap

Procedure

1. 1

   Disconnect fuel inlet line
   Using a line wrench of the correct size (verify on the fitting, commonly 5/8") on the inlet fitting nut (larger line from fuel tank), hold the fuel pump inlet fitting steady with a wrench while loosening the line nut. Expect fuel spillage. Allow fuel to drain into container. Inspect line condition for cracks or damage.
2. 2

   Disconnect fuel outlet line
   Using a 5/8" line wrench on the outlet fitting nut (line to carburetor), hold the fuel pump outlet fitting steady while loosening the line nut. Catch any remaining fuel. Move fuel lines clear of pump body.
3. 3

   Remove fuel pump mounting bolts
   Remove the 2 fuel pump mounting bolts using a 9/16" socket. Support the fuel pump body with one hand as you remove the second bolt to prevent it from falling and damaging fuel line ports.
4. 4

   Extract fuel pump and pushrod
   Carefully pull the fuel pump away from the engine block. The fuel pump actuating arm will disengage from the pushrod. Immediately retrieve the pushrod from the block bore using fingers or magnetic pickup tool. The pushrod is approximately 6 inches long and should slide out easily. Do not allow it to fall into the engine.
5. 5

   Inspect pushrod and bore
   Examine the pushrod for wear on both ends. The camshaft end should have a smooth, slightly domed wear pattern. The pump end should show even contact wear. Check pushrod length against new part (original length approximately 6.10 inches). If wear exceeds 0.030 inches or if pitting is present, replace pushrod. Inspect the block bore for scoring or debris.
6. 6

   Clean mounting surface
   Use gasket scraper to remove all old gasket material from engine block mounting pad. Ensure mounting surface is completely clean and flat with no residual gasket material or sealant. Clean with brake cleaner and wipe dry. Inspect block mounting surface for cracks or damage.
7. 7

   Verify new pump operation
   Before installation, manually actuate the new pump lever through its full stroke several times. Confirm smooth operation with spring return. Check that inlet and outlet check valves seat properly by attempting to blow backwards through each port (you should not be able to).
8. 8

   Position pushrod and rotate engine
   Insert pushrod into block bore with chamfered end toward camshaft eccentric. Rotate engine crankshaft clockwise (using socket on harmonic balancer bolt) until pushrod is at its lowest point in travel. This positions camshaft eccentric to allow easiest pump installation.
9. 9

   Install new pump gasket
   Position new fuel pump gasket on engine block mounting studs or align with mounting bolt holes. Gasket may be held in place with small dabs of grease if necessary. Ensure gasket holes align perfectly with block mounting holes and pushrod bore.
10. 10

    Install fuel pump
    Hold pushrod in place with one finger through the pump mounting hole while positioning pump against block. Align pump actuating arm with pushrod top. Press pump firmly against block while ensuring pushrod engages pump arm correctly. Start both mounting bolts by hand to retain pump.
11. 11

    Torque mounting bolts
    Torque both fuel pump mounting bolts to the manufacturer-specified value (verify against GM service manual; typically approximately 25 ft-lbs), alternating between bolts to seat the pump evenly. Do not overtighten as this can distort pump housing and cause internal leakage or crack the pump body casting.
12. 12

    Reconnect fuel lines
    Note that the inverted flare fuel line fittings seal metal-to-metal and normally require no gaskets or crush washers. Thread inlet line nut onto pump inlet fitting by hand until snug, then tighten with line wrench an additional 1/2 turn while holding pump fitting steady. Repeat for outlet line. Do not overtighten as this can strip soft brass fittings or crack fuel lines.
13. 13

    Prime fuel system
    Reconnect negative battery cable. Place clean rag around fuel line connections at pump. Have assistant crank engine for 5-10 seconds without starting (disable ignition by disconnecting coil wire). Observe pump action and fuel line connections for leaks. Repeat cranking cycles if necessary until fuel reaches carburetor.
14. 14

    Start engine and check for leaks
    Reconnect coil wire and start engine. Allow engine to idle. Carefully inspect all fuel line connections at pump for seepage or drips. Check pump body mounting gasket area for fuel weeping. Any fuel leakage requires immediate shutdown and correction.

Reassembly

1. Reinstall air cleaner assembly if removed
2. Wipe down all fuel residue from engine bay and pump area
3. Dispose of old fuel pump and gasoline-soaked rags properly according to local regulations

Verification

• Engine starts promptly without extended cranking
• Engine idles smoothly without fuel starvation symptoms
• No fuel odor present during or after operation
• All fuel line connections remain dry after 15 minutes of engine operation
• Fuel pump operates quietly without rattling or knocking sounds
• Fuel pressure at carburetor inlet measures 5-7 psi with mechanical gauge if available

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