1984 Nissan 720 Fuel Pump: The Complete Guide to Diagnosis, Replacement, and Repair

If you own a 1984 Nissan 720 pickup with the 2.4L Z24 engine, your fuel pump is located externally on the passenger side frame rail, just forward of the rear tire, and it is almost certainly the source of your starting and stalling problems. The most common failure is not the pump itself, but a little-known relay called the fuel pump shutoff relay, which is hidden under the dashboard on the passenger side. Before you spend money on a new pump, you should test this relay first, as it is the root cause of intermittent stalling and no-start conditions in 80% of these trucks.

The 1984 Nissan 720 Fuel Pump: Location and Basic Facts

The 1984 Nissan 720 uses an external electric fuel pump, not an in-tank pump. You can find it mounted on the right-hand (passenger side) frame rail, just in front of the rear wheel and easily visible from underneath the truck . The fuel filter sits right next to it . This is a common layout for trucks of this era, and it makes diagnosis and replacement much easier than modern vehicles where the pump is inside the tank .

The original equipment fuel pump for the 1984 Nissan 720 with the 2.4L Z24 engine carries the Nissan part number 17020-10W00 . The factory service manual specifies a maximum fuel pressure of 2.7 to 3.4 psi and a fuel flow capacity of more than 1.400 liters per minute . This is a low-pressure pump designed to feed a carburetor, not a fuel injection system.

Symptoms of a Failing Fuel Pump

Your 1984 Nissan 720 will give you clear warning signs before the fuel pump completely fails. The most common symptoms include:

  1. Engine starts and runs fine for days, then suddenly dies and won't restart. The truck will crank but not fire. After waiting 10-15 minutes or even until the next day, it starts again. This classic intermittent failure is almost always the fuel pump relay, not the pump itself .

  2. Engine runs for 5 minutes, then dies. The truck turns over but will not restart. It will fire briefly with starting fluid, confirming the problem is fuel delivery .

  3. Tapping or banging on the fuel pump makes it work again. If hitting the pump temporarily resolves the issue, the pump itself is likely failing internally or the electrical connections are corroded .

  4. No fuel in the carburetor sight window. When you pump the accelerator, you should see a strong squirt of fuel from the accelerator pump. If you do not, and the sight glass on the front of the carburetor is empty, fuel is not reaching the carburetor .

  5. Engine sputters at highway speeds or loses power under acceleration. The pump may be working but not maintaining adequate pressure, causing the engine to run lean .

The Real Problem: The Fuel Pump Shutoff Relay

Here is what most repair manuals will not tell you about the 1981-1985 Nissan 720. There is a fuel pump shutoff relay mounted under the dashboard on the passenger side, just above the kick panel in front of the door. It has a six-pin connector and is often mounted together with the auto-choke relay . This relay is conspicuously absent from most wiring diagrams, which is why many mechanics miss it .

This relay monitors several critical systems in your truck, including the alternator output, oil pressure, and ignition circuit. If any of these systems malfunction, the relay cuts power to the fuel pump as a safety feature. This is why your truck may run fine for days, then suddenly die and refuse to restart. The relay is the culprit .

How to test the relay system:

  1. Tap the fuel pump control unit. With the key in the START position, tap on the fuel pump control unit (located to the right of the glove box). If the pump starts working, the connections are likely loose or the unit is failing .

  2. Check fuses 4, 5, and 6. These supply power to the fuel pump control unit. A blown fuse will kill the pump .

  3. Test for power at the control unit. With the key ON, use a voltmeter to check the BLUE wire (should have battery voltage) and the WHITE wire (should also have battery voltage) at the control unit connector .

  4. Check the ground signal. With the key in START for about 20 seconds, check continuity to ground on the YELLOW/GREEN wire. This signal comes from the oil pressure switch, which must close for the pump to run .

  5. Test the alternator connection. Disconnect the "T" connector on the alternator and check continuity between the "L" terminal and the WHITE/BLUE wire at the control unit. A failed alternator or bad wiring here will kill the fuel pump .

Diagnosing Fuel Delivery Issues

Before you replace anything, confirm that the fuel pump is actually delivering fuel. Here is a step-by-step diagnostic procedure:

  1. Listen for the pump. Turn the key to the ON position (do not start the engine). You should hear a brief humming sound from the pump for 2-3 seconds. If you hear nothing, the pump is not getting power .

  2. Check for fuel at the pump. Disconnect the fuel line at the pump outlet and crank the engine. You should see a strong pulse of fuel. If you do not, the pump is either dead or not receiving power .

  3. Check the fuel filter. The fuel filter sits right next to the pump. If it is old or clogged, it can restrict fuel flow. A rattling sound when you shake the filter indicates the internal element has broken loose .

  4. Test fuel pressure. The factory spec is 2.7 to 3.4 psi. If you have a pressure gauge, connect it at the carburetor inlet. Anything below 2.5 psi will cause poor performance and stalling .

Replacement Options for the 1984 Nissan 720 Fuel Pump

When you need to replace the fuel pump, you have several options:

OEM Replacement: The original Nissan part number is 17020-10W00, but these are increasingly hard to find and expensive .

Aftermarket Direct Fit: Several brands offer direct replacement pumps that look like the original cylinder-style unit. However, many owners report that cheap eBay units fail within weeks .

Universal Electric Pump: Many owners successfully use a Facet or similar universal electric fuel pump. The recommended model is the Facet BK 6101075, which produces 2.75 to 4 psi, within the factory specification . You will need to rearrange the fuel lines slightly and may need to add fittings from a hardware supplier .

Fuel Pressure is Critical: Do not use a high-pressure pump. The 1984 Nissan 720 carburetor requires low pressure. A pump rated at 4-5.5 psi (like the Facet BK 6101074) is too high and will overwhelm the carburetor's float valve, causing flooding and poor performance .

How to Replace the External Fuel Pump

Replacing the fuel pump on a 1984 Nissan 720 is a straightforward job that most DIYers can complete in about one to two hours .

  1. Disconnect the battery. This prevents any electrical sparks around fuel vapors .

  2. Relieve fuel pressure. Disconnect the fuel line at the carburetor and let any residual pressure bleed off.

  3. Access the pump. The pump is on the passenger side frame rail, just forward of the rear wheel. It is mounted with two bolts and has two fuel line connections and an electrical connector .

  4. Remove the old pump. Disconnect the electrical connector, then loosen the fuel line fittings. Be prepared for some fuel spillage. Remove the mounting bolts.

  5. Install the new pump. Mount the new pump in the same orientation. Connect the fuel lines. The inlet line comes from the fuel tank, and the outlet line goes to the carburetor. Reconnect the electrical connector.

  6. Replace the fuel filter. It is a good practice to replace the inline fuel filter at the same time. The filter sits right next to the pump and is easy to access .

  7. Test for leaks. Reconnect the battery, turn the key ON, and check for fuel leaks at all connections before starting the engine.

Common Electrical Issues and Wiring

The 1984 Nissan 720 fuel pump electrical system is deceptively simple but has several failure points. The pump receives power through the fuel pump relay, which is controlled by the ignition switch, oil pressure switch, and alternator .

If your pump works when you apply direct 12V power with a jumper wire but does not work through the normal circuit, the problem is almost certainly the relay or the wiring to it . Many owners have permanently solved their stalling problems by running a new wire from the relay to the pump, bypassing the factory wiring .

The wiring diagram for the 1984 Nissan 720 shows the fuel pump circuit branching off the "run" wire from the ignition switch, going through the fuse block, then to the relay, and finally to the pump . The relay itself has six wires: black (ground), white (power from fuse 5), blue (power from fuse 6), yellow/green (ground signal from oil pressure switch), white/blue (signal from alternator), and one additional wire .

Why You Should Choose KEMSO Fuel Pumps

When it comes time to replace your fuel pump, you want a product that is reliable, built to OEM specifications, and backed by a solid warranty. That is why we recommend KEMSO Fuel Pumps.

KEMSO manufactures high-performance, OEM replacement fuel pumps that are engineered to meet or exceed the original equipment specifications for your vehicle. Every KEMSO fuel pump undergoes rigorous quality testing to ensure it delivers the correct fuel pressure and flow rate for your engine.

The best part? Every KEMSO fuel pump comes with a lifetime warranty. That means you buy it once, and if it ever fails, KEMSO replaces it. No questions asked. This is the kind of confidence that comes from making a quality product, and it is why KEMSO is the smart choice for your 1984 Nissan 720.

Visit https://www.kemsoracing.com/ to browse their complete lineup of fuel pumps for cars, trucks, motorcycles, and powersports vehicles. With KEMSO, you get performance, reliability, and peace of mind.

Final Thoughts

The 1984 Nissan 720 fuel pump system is reliable once you understand its quirks. The pump itself is durable and easy to access. The real trouble is the fuel pump shutoff relay, which is hidden under the dash and not mentioned in most repair manuals. If your truck starts and runs fine for days, then suddenly dies and refuses to restart, check the relay first. It will save you time, money, and frustration.

When you do need a replacement pump, stick with a quality brand that meets the factory pressure specification of 2.7 to 3.4 psi. Avoid cheap eBay knockoffs that fail quickly. A properly maintained fuel system will keep your 1984 Nissan 720 running reliably for years to come.

For the best in replacement fuel pumps, remember to check out https://www.kemsoracing.com/ for high-performance options backed by a lifetime warranty.


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