Fuel Pump Relay

Replace the fuel pump relay, which controls power to the electric fuel pump. Located in the Power Distribution Center (PDC) under the hood.

Warnings

Tools required

Parts

• Fuel pump relay × 1 — Mopar 4638115 or equivalent micro relay

Preparation

1. Park vehicle on level ground and engage parking brake.
2. Turn ignition to OFF position and remove key.
3. Allow engine to cool if recently operated.
4. Open hood and secure with prop rod.
5. Identify the Power Distribution Center (PDC) on the driver's side firewall near the brake master cylinder. It is a black plastic box with a removable cover.

Procedure

1. 1

   Disconnect battery negative terminal
   Locate the battery in the right rear cargo area behind the seats. Using a 10mm socket, loosen the negative (black, marked -) battery terminal bolt and remove the cable from the battery post. Secure the cable away from the battery to prevent accidental contact.
   Torque spec

   Battery Terminal Bolts7 Nm (5 lb-ft)
2. 2

   Remove PDC cover
   Locate the Power Distribution Center / relay block per the vehicle's service documentation (verify exact location for this 1992 Viper). The PDC cover has tabs on each side. Press the release tabs simultaneously and lift the cover straight up to remove. Set the cover aside with the inside facing up to reference the relay diagram printed on the underside.
3. 3

   Identify fuel pump relay location
   Examine the relay diagram printed on the inside of the PDC cover. The fuel pump relay is typically located in the front row of the relay block and is labeled 'FUEL PUMP' or 'ASD/FUEL'. Note the relay position before removal. The relay is a standard rectangular ISO automotive relay with five blade terminals; confirm the terminal count and size against the removed relay.
4. 4

   Remove old fuel pump relay
   Grasp the fuel pump relay firmly between thumb and forefinger. Pull straight up with steady pressure to release the relay from its socket. If the relay is difficult to remove, use needle-nose pliers to grip the relay body (not the terminals) and pull straight up. Avoid rocking side to side, which can damage the socket terminals.
   ⚠Do not pull on the relay terminals or wiring. Pull only on the relay body to prevent terminal damage.
5. 5

   Inspect relay socket
   Examine the relay socket for corrosion, damage, or bent terminals. The socket should have clean, spring-tension terminals that are not discolored or pushed back into the housing. If corrosion is present, clean the terminals with electrical contact cleaner and allow to dry completely. If terminals are damaged or pushed back, the PDC socket may require professional repair or replacement.
6. 6

   Install new fuel pump relay
   Verify the new relay matches the pin configuration of the old relay (check the terminal count and arrangement on the bottom of the relay). Optional: apply a small amount of dielectric grease to the relay terminals to prevent corrosion. Align the relay terminals with the socket, ensuring correct orientation (the relay will only fit one way). Press the relay straight down into the socket with firm, even pressure until it seats fully and is flush with adjacent relays.
   ⚠Ensure the relay is fully seated. A partially inserted relay will cause intermittent fuel pump operation or complete failure.
7. 7

   Reinstall PDC cover
   Position the PDC cover over the relay block, aligning the cover tabs with the slots in the PDC housing. Press down firmly on all four corners until the cover clicks into place and is fully seated.
8. 8

   Reconnect battery negative terminal
   Return to the rear cargo area. Place the negative battery cable onto the negative battery post. Thread the terminal bolt by hand to ensure proper engagement, then tighten to approximately 5-7 ft-lbs (60-84 in-lbs) using a 10mm socket; confirm exact spec in service documentation.
   Torque spec

   Battery Terminal Bolts7 Nm (5 lb-ft)

Reassembly

1. Ensure the PDC cover is fully latched with no gaps around the perimeter.
2. Verify the battery terminal is tight and the cable cannot be moved by hand.
3. Close the hood securely.

Verification

• Turn the ignition key to the ON position (do not start the engine). Listen for the fuel pump to run for approximately 2 seconds, then stop. This primes the fuel system and confirms relay operation.
• Start the engine and verify it runs normally without hesitation or stalling.
• Check for any warning lights on the instrument cluster, particularly the Check Engine light.
• Turn the engine off and restart it at least two more times to confirm consistent fuel pump operation.
• If the fuel pump does not activate or the engine does not start, immediately turn off the ignition and verify relay installation and seating.

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