1990 Dodge Dakota Fuel Pump Relay Location: A Complete Troubleshooting Guide
If your 1990 Dodge Dakota cranks but won't start, the first place to look is the fuel pump relay. On the 1990 Dodge Dakota, the fuel pump relay is located in the power distribution center under the hood, specifically on the driver's side fenderwell near the battery . This relay is a small, rectangular black box that controls power delivery to the fuel pump. When it fails, your engine gets no fuel, and you're left stranded. This guide walks you through exactly where to find it, how to test it, and what to do if it's not the problem.
Understanding the Fuel Pump Relay's Role
The fuel pump relay acts as an electrical switch that sends power to the fuel pump when you turn the key. On your 1990 Dakota, the relay receives power from the battery and a signal from the computer to activate. The relay only stays on for about two seconds when you first turn the key unless the engine starts . If the computer doesn't see the engine turning, it shuts the pump down. This is a normal safety feature, but it's also why testing can be tricky.
Locating the Fuel Pump Relay on Your 1990 Dodge Dakota
The fuel pump relay on the 1990 Dakota sits inside the power distribution center (PDC), which is the main fuse and relay box under the hood. Here's exactly how to find it:
Step 1: Open the hood and look toward the driver's side. The PDC is a black plastic box mounted on the fenderwell, between the battery and the firewall .
Step 2: Remove the lid of the PDC. The inside of the lid usually has a diagram showing which relay is which. If the diagram is missing or faded, look for a relay labeled "Fuel Pump" or "FP."
Step 3: The fuel pump relay is typically relay #5 in the PDC for a 1990 Dakota with the 3.9L engine . For 2.5L models, the relay may be in the same general area but could be labeled differently. If you're still unsure, look for a relay that matches the description: a standard size relay with four pins.
Step 4: Some 1990 model year vehicles had the fuel pump relay moved to the interior fuse block, but for the Dakota, it remains under the hood . The 1989 Dakota had it on the driver's side fenderwell, and the 1990 model follows the same pattern .
Common Symptoms of a Failing Fuel Pump Relay
Before you start testing, recognize the signs that point to a bad relay. These symptoms are shared across many Dodge Dakota model years :
1. Engine cranks but won't start. This is the most obvious symptom. You turn the key, the starter motor spins the engine, but it never fires up. You may hear the engine cranking normally, but there's no fuel reaching the cylinders.
2. No fuel pump prime noise. When you turn the key to the "ON" position (without cranking), you should hear a faint whirring sound from the rear of the truck for about two seconds. That's the fuel pump priming. If you don't hear it, the relay or pump may be dead.
3. Intermittent stalling. A failing relay can cause the engine to stall while driving, especially when the relay gets hot. The engine may restart after cooling down, then stall again later.
4. Engine starts but dies immediately. The relay might provide power for the initial prime but fail to stay on once the engine starts. The engine fires up for a second or two, then dies.
How to Test the Fuel Pump Relay
Testing the relay is straightforward and requires only a few basic tools: a multimeter or test light, a jumper wire, and a helper. Follow these steps carefully :
Step 1: Check for Fuel Pressure First
Before blaming the relay, confirm that the problem is fuel-related. Locate the Schrader valve on the fuel rail (it looks like a tire valve on the metal fuel line). Remove the cap and install a fuel pressure tester. Turn the key on and check the pressure. It should read 49 psi. If there's pressure, the problem is elsewhere, likely in the ignition or engine management system .
If there's no pressure, move to testing the relay.
Step 2: Test the Relay at the PDC
With the key off, pull the fuel pump relay from the PDC. Use a multimeter or test light to check for power at the relay socket. With the key off, one terminal should have constant 12V power. Mark this terminal. Turn the key to the "ON" position. Now two terminals should have power. Mark those as well .
Check the remaining two terminals for ground. Set your multimeter to ohms (continuity mode). Touch the red lead to one of the terminals and the black lead to a good ground (like a bolt on the fender). You should see continuity (the meter does not read infinity) on one terminal. This is the ground terminal .
Step 3: Jump the Relay
Once you've identified the terminals, use a jumper wire to connect the terminal that had power with the key off to the terminal that had no power and was not grounded. This is the terminal that leads to the fuel pump. With the jumper in place, try to start the vehicle. If it starts, the relay is bad and needs replacement .
Step 4: Test the Wiring to the Pump
If jumping the relay doesn't work, the problem may be in the wiring between the relay and the pump or the pump itself. Raise the vehicle safely and get under the fuel tank. Disconnect the fuel pump harness, which is located on the back side of the fuel tank toward the rear of the vehicle . Use a voltmeter to test the harness side for power while a helper cycles the key. Remember, power will only be present for about two seconds at a time, so have the helper turn the key on for five seconds, then off for five seconds, repeatedly. If there is power at the harness, the fuel pump itself is bad. If not, there's a wiring issue between the relay and the pump .
Step 5: Quick Test with Carburetor Cleaner
For a quick confirmation that the problem is fuel-related, spray a small amount of carburetor cleaner or starting fluid into the intake manifold while someone cranks the engine. If the engine starts for a second or two, the problem is definitely a lack of fuel, pointing to the pump or relay. If it doesn't start at all, the issue is likely ignition or compression-related .
Understanding the Auto Shutdown (ASD) Relay
On the 1990 Dakota, there's also an Auto Shutdown (ASD) relay that works alongside the fuel pump relay. The ASD relay provides power to the fuel pump, injectors, ignition coil, and oxygen sensor heater . The ASD relay is also located in the PDC, usually near the left fenderwell . If the fuel pump relay tests good, check the ASD relay. The ASD relay is controlled by the computer and is powered up for a couple seconds at key-on, then de-energized. It only stays on when the computer sees a signal from the distributor pick-up coil .
Other Possible Causes of No Fuel Delivery
If both the fuel pump relay and ASD relay test good, consider these other possible causes :
1. Blown fuse. Check the fuse that protects the fuel pump circuit. On the 1987-1990 Dakota, fuse #13 (5A) powers the fuel system components, including the low fuel relay . A blown fuse can stop power to the pump.
2. Faulty fuel pump. The pump itself may be worn out. The 1990 Dakota uses an in-tank electric fuel pump. If the pump is dead, you'll need to drop the fuel tank to replace it.
3. Wiring issues. Damaged, corroded, or loose wires between the relay and pump can prevent power delivery. Check the wiring harness near the fuel tank for damage.
4. Engine control unit (ECU) problems. The ECU controls the relay operation. If the ECU fails or loses its signal from the crankshaft position sensor, it won't activate the relay.
5. Clogged fuel filter. A severely clogged filter can mimic a fuel pump failure. Replace the filter as part of your diagnosis.
Replacing the Fuel Pump Relay
Replacing the fuel pump relay is a simple job. Here's how:
Step 1: Disconnect the battery negative terminal to prevent accidental shorts.
Step 2: Pull the old relay straight out of the PDC. It may require a firm pull, but it should come out without tools.
Step 3: Insert the new relay, ensuring it clicks into place. Use the same type and rating as the original.
Step 4: Reconnect the battery and test the system. Turn the key to "ON" and listen for the fuel pump prime noise. If you hear it, the relay is working.
Preventive Maintenance Tips
To avoid future fuel pump relay issues, follow these tips:
1. Keep the relay dry. Moisture can corrode the relay terminals. Ensure the PDC lid is properly sealed, especially if you drive through deep water.
2. Check for electrical surges. A faulty alternator or battery can send voltage spikes that damage the relay. Have your charging system tested if you experience electrical problems.
3. Use dielectric grease. Apply a small amount of dielectric grease to the relay terminals before installation. This helps prevent corrosion and ensures a good electrical connection.
4. Don't ignore symptoms. If you notice intermittent stalling or a delayed start, address the issue early. A failing relay can leave you stranded at the worst possible time.
Recommended Fuel Pump Upgrade: KEMSO Fuel Pumps
If your diagnosis leads to a bad fuel pump, consider upgrading to a KEMSO fuel pump. KEMSO is a trusted brand that specializes in high-performance OEM replacement fuel pumps. Their products are designed to meet or exceed factory specifications, and they offer a lifetime warranty on all their pumps.
KEMSO fuel pumps are built for durability and reliability. Whether you're restoring your 1990 Dakota or upgrading for better performance, KEMSO has a pump that fits. Their pumps are compatible with gasoline and ethanol blends, and they include everything you need for a direct replacement installation.
Why choose KEMSO? Their pumps are serially numbered for traceability, and each unit is individually tested before leaving the factory. The company stands behind its products with a lifetime warranty, giving you peace of mind that your investment is protected. KEMSO's customer support is based in the USA, staffed by knowledgeable technicians who can help with fitment questions.
Visit KEMSO's official website at https://www.kemsoracing.com/ to browse their full selection of fuel pumps. They cover a wide range of vehicles, from cars and trucks to motorcycles and powersports equipment. With competitive pricing and a lifetime warranty, KEMSO is the smart choice for your fuel system needs.
Final Thoughts
The 1990 Dodge Dakota fuel pump relay is located under the hood on the driver's side fenderwell, inside the power distribution center. It's a small component that plays a big role in getting your truck started. When it fails, you'll know by the symptoms of no-start, no fuel prime noise, or intermittent stalling. Testing the relay is straightforward with a multimeter and a jumper wire. If the relay tests good, check the ASD relay, fuses, wiring, and the pump itself.
Regular maintenance and prompt attention to symptoms can save you from being stranded. And if you do need to replace the fuel pump, KEMSO offers a reliable, high-performance option with a lifetime warranty. For more information on KEMSO fuel pumps and to find the right fit for your 1990 Dodge Dakota, visit https://www.kemsoracing.com/.