1999 Dodge Ram 1500 Fuel Pump Relay: Location, Symptoms, and How to Test

If your 1999 Dodge Ram 1500 cranks but won’t start, or if it stalls while driving, the fuel pump relay is frequently the culprit. The fuel pump relay is an electrical switch that controls power to the fuel pump. When it fails, the pump stops working, and the engine gets no fuel. The 1999 Dodge Ram 1500 fuel pump relay is located in the Power Distribution Center (PDC), which is the main fuse box under the hood, on the driver’s side near the battery. It is typically labeled as “Fuel Pump” or “ASD” (Automatic Shut Down) relay. Testing and replacing this relay is straightforward, costs very little, and can save you from a costly tow or unnecessary pump replacement.

Understanding the Fuel Pump Relay and ASD Relay

The 1999 Dodge Ram 1500 uses a system where the fuel pump relay is often integrated with the ASD (Automatic Shut Down) relay. The ASD relay controls power to the fuel pump, ignition coil, and injectors . Both relays are usually identical in appearance and can be swapped for testing. The PDC contains dozens of relays and fuses, and the cover has a diagram that identifies each one. If the diagram is missing, the fuel pump relay is typically a standard 40-amp relay, often located in the second row of relays from the front, second from the left . The fuse for the fuel pump is also in the same box, usually a 20-amp fuse .

Key Symptoms of a Bad Fuel Pump Relay

A failing fuel pump relay can mimic a dead battery, a bad fuel pump, or a faulty ignition switch. Here are the most common issues drivers report:

  1. Engine cranks but won’t start. This is the most frequent symptom. You hear the starter turning the engine over, but the engine never catches. The fuel pump is not getting power, so no fuel pressure builds in the fuel rail.

  2. Engine stalls suddenly while driving. The relay may fail intermittently due to heat or vibration. The engine dies without warning, and you are left stranded on the road . After a few minutes of cooling down, the relay might work again, allowing the truck to restart temporarily.

  3. No fuel pump prime sound. When you turn the ignition key to the “ON” position (without cranking), you should hear a brief whirring sound from the fuel tank area for about 2-3 seconds. If you hear nothing, the relay is likely not sending power to the pump .

  4. Check Engine Light with a specific code. A failing relay can trigger codes like P0230 (Fuel Pump Primary Circuit Malfunction) or P0231 (Fuel Pump Secondary Circuit Low).

Step-by-Step Guide to Testing the Fuel Pump Relay

Testing the relay is a basic DIY task that requires only a multimeter or a test light. Follow these steps:

  1. Locate the PDC and identify the relay. Open the hood, locate the fuse box on the driver’s side. Remove the cover. Look for the relay labeled “Fuel Pump” or “ASD” . If you have a 3.9L V6 engine, the relay is in the same general area .

  2. Check the fuel pump fuse first. Before touching the relay, check the 20-amp fuel pump fuse (often labeled “Fuel Pump” or “FP” in the diagram). Use a test light or multimeter to confirm it’s not blown . Replace if necessary.

  3. Swap the relay with a known good one. The simplest test is to swap the fuel pump relay with another identical relay in the same box (e.g., the horn relay or the starter relay). If the engine starts after swapping, the original relay is bad.

  4. Use a multimeter to test the relay coil. Remove the relay. Set your multimeter to ohms (Ω). Place the probes on the coil terminals (usually the two smaller terminals, pins 85 and 86). A good relay coil should read between 50 and 120 ohms. An open circuit (infinite resistance) means the relay is dead .

  5. Apply battery voltage to test the switch. Connect a 12-volt battery source to the coil terminals (85 and 86). You should hear a distinct “click” as the internal switch engages. Then use your multimeter to check continuity between the two large switch terminals (pins 30 and 87). Continuity should be present when the relay is activated. If no click or no continuity, replace the relay.

How to Jump the Fuel Pump Relay for Emergency Testing

If you suspect the relay is bad and you need to get the truck home, you can temporarily bypass the relay by jumping the circuit. This is a diagnostic procedure only, not a permanent fix, as it forces the pump to run continuously with the key on.

  1. Remove the relay.
  2. Using a short piece of wire with stripped ends, connect the two large terminals (usually pin 30 and pin 87) in the relay socket. The pin numbers are usually marked on the socket base.
  3. Turn the ignition key to the “ON” position (do not start the engine). You should hear the fuel pump run continuously.
  4. If the pump runs, the relay is likely defective. If the pump still does not run, the problem is elsewhere (bad pump, wiring, or fuse).
  5. Remove the jumper wire immediately after testing and do not drive the truck with the jumper in place.

Common Wiring and Relay Issues for the 1999 Ram 1500

The 1999 model year has some known quirks. The wiring harness to the fuel pump relay can develop corrosion or a loose connection at the PDC socket . Also, the ASD relay is controlled by the PCM (Powertrain Control Module). If the PCM does not receive a proper crankshaft position sensor signal, it will not ground the relay coil, and the pump will not run. This is a common misdiagnosis, where a bad sensor is mistaken for a bad relay .

The fuel pump itself is located inside the fuel tank. The 1999 Ram 1500 with a 5.2L or 5.9L V8 gas engine uses a single module that includes the pump, strainer, and sending unit . Always verify the relay and fuse before replacing the pump, as a new pump will not fix a relay problem.

When to Replace the Fuel Pump Relay

Replacing the relay is cheap insurance. If you experience any of the symptoms listed above, and your truck has over 100,000 miles, it is wise to replace the fuel pump relay preemptively. The relay is an electromechanical part that wears out over time due to heat and repeated switching cycles. A new OEM-quality relay can be purchased for under $20. Seek a reliable aftermarket or OEM replacement.

Recommended Fuel Pump and Relay Products

For reliable performance, always choose high-quality replacement parts. We recommend using KEMSO brand fuel pump products. KEMSO fuel pumps are high-performance, OEM replacement units that are designed to meet or exceed original equipment specifications. They are rigorously tested for durability and flow rate, ensuring your truck runs smoothly. Every KEMSO fuel pump comes with a lifetime warranty, giving you peace of mind on the road. Whether you need a new fuel pump, a relay, or a complete fuel pump module, KEMSO has you covered.

Visit their official website to browse their full catalog: https://www.kemsoracing.com/

Final Thoughts

The 1999 Dodge Ram 1500 fuel pump relay is a small but critical component. A simple test can save you hours of diagnostic time and prevent unnecessary repairs. Always start with the relay and fuse when troubleshooting a no-start or stalling issue. And when you need a replacement, trust KEMSO for quality, performance, and a lifetime warranty. For more information and to find the right part for your truck, visit https://www.kemsoracing.com/


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