1987 Jeep Comanche Fuel Pump: The Complete Guide to Diagnosis, Replacement, and Best Options

If you own a 1987 Jeep Comanche and your truck is struggling to start, sputtering under load, or dying unexpectedly, the fuel pump is likely the culprit. The 1987 Jeep Comanche uses an electric fuel pump located inside the fuel tank, and when it fails, your engine simply won't get the fuel it needs to run. Replacing the fuel pump is a straightforward job that most DIYers can handle in a weekend, and the cost for a quality pump ranges from $50 to $150 depending on the brand and whether you need a complete sending unit assembly . This guide walks you through everything you need to know—from symptoms and diagnosis to step-by-step replacement and the best fuel pump options on the market today.

How the 1987 Jeep Comanche Fuel Pump Works

The 1987 Comanche came with either a 2.5L four-cylinder or a 4.0L inline-six engine, and both use an in-tank electric fuel pump . Unlike older mechanical pumps mounted on the engine, the electric pump sits inside the fuel tank and pushes fuel under pressure to the fuel injection system. The pump is part of a larger assembly that includes the fuel level sending unit, so when you replace the pump, you often replace the whole unit . The pump runs for a few seconds when you turn the key to the ON position to prime the system, then continues running while the engine is cranking or running .

Signs Your 1987 Jeep Comanche Fuel Pump Is Failing

The most common symptom is an engine that cranks but won't start. If you turn the key and hear the starter turning but the engine never fires, your fuel pump may not be delivering fuel. Here are the specific warning signs to watch for:

1. No priming noise – When you turn the key to ON, you should hear a two- to three-second hum from the fuel tank area. If you hear nothing, the pump is likely dead .
2. Engine sputters at high speeds – A failing pump can't maintain enough pressure, causing the engine to hesitate or surge when you accelerate.
3. Loss of power under load – When climbing hills or hauling a load, the engine may feel weak or start to cut out.
4. Engine dies and won't restart – The pump may work intermittently, causing the engine to stall and then refuse to restart until it cools down.
5. Low fuel pressure – A fuel pressure gauge will show readings below the factory specification of 30-40 PSI for the 2.5L engine .

How to Diagnose the Fuel Pump Before Replacing It

Before you drop the fuel tank, take a few minutes to confirm the pump is actually the problem. This will save you time and money.

Step 1: Listen for the pump. Remove the gas cap and have an assistant turn the key to ON while you listen at the filler neck. A working pump will hum for two to three seconds .

Step 2: Check the fuel pump fuse and relay. Locate the fuse box under the dash or in the engine bay. Find the fuel pump fuse and relay, and inspect them. If the fuse is blown, replace it with one of the same amperage. If the relay is faulty, swap it with a known good relay of the same type .

Step 3: Test for power and ground. If the fuse and relay are good, use a multimeter to check for 12 volts at the fuel pump electrical connector. If you have power and ground but the pump doesn't run, the pump itself is bad .

Step 4: Check fuel pressure. Connect a fuel pressure gauge to the test port on the fuel rail. For the 2.5L engine, you should see 30-40 PSI at idle. If the pressure is low or zero, the pump is likely failing .

Fuel Pump Options for the 1987 Jeep Comanche

The 1987 Comanche uses different pumps depending on the engine and fuel tank size. Here are the most common replacement options:

For 1987-1990 Jeep Comanche with 4.0L engine (18 or 23.5-gallon tank): You need a fuel pump sending unit assembly that fits the side-mounted tank. The part numbers include JPSU-6 and JPSU-6P4.0, and the assembly typically includes the pump, sending unit, lock ring, and O-ring . The pressure range is 90-110 PSI with a flow rate of 45 GPH .

For 1987-1990 Jeep Comanche with 2.5L engine: The fuel pump is also in-tank, and you can use a pump that fits the 2.5L fuel-injected engine. The Herko K4032 pump is compatible with 1986-1990 Comanche models with the 2.5L engine . Another option is the TREX30-731a pump, which provides 30-40 PSI and a flow rate of 140 LPh .

For 1991-1993 Jeep Comanche (both engines): The Herko K4033 electric fuel pump is an OE upgrade unit that fits 1991-1993 Comanche models with both 2.5L and 4.0L engines . The OMIX 17709.09 pump also fits 1991-1993 Comanche models with the 2.5L engine and 1987-1993 models with the 4.0L engine .

Top-rated aftermarket options: The YHTAUTO Electric Fuel Pump Sending Unit is designed for 1987-1992 Jeep Comanche with 2.5L and 4.0L engines. It features durable POM construction, easy plug-in connectors, and quiet operation . The ANTUKO Fuel Tank Sending Unit is another good choice for 1987-1990 Comanche models, offering stable fuel pressure and easy installation .

How to Replace the Fuel Pump on a 1987 Jeep Comanche

Replacing the fuel pump requires dropping the fuel tank, but the job is manageable with basic tools. Plan for about 1-2 hours of work .

Tools and supplies you'll need: New fuel pump assembly, socket set, screwdrivers, pliers, jack and jack stands, blocks of wood, siphon pump and gas can, safety glasses, and gloves .

Step 1: Relieve fuel system pressure. Disconnect the negative battery cable. Remove the fuel pump fuse or relay, then crank the engine for a few seconds until it stalls. This relieves pressure in the fuel lines .

Step 2: Drain the fuel tank. If the tank is more than half full, use a siphon pump to drain fuel into an approved gas can. This makes the tank lighter and easier to handle .

Step 3: Disconnect everything at the tank. The 1987 Comanche has the fuel pump/sending unit on top of the tank. Disconnect the fuel vent, supply, and return hoses, and label them so you know which is which. Also disconnect the electrical harness connector .

Step 4: Support and lower the tank. Place a jack with a block of wood under the fuel tank for support. Remove the retaining straps or bolts that hold the tank to the frame. Carefully lower the tank just enough to access the top of the pump assembly .

Step 5: Remove the old pump assembly. The pump is held in place by a cam lock ring. Turn the inner ring counterclockwise using a wood dowel or brass punch—never use a steel tool that could create sparks . Lift the assembly out of the tank.

Step 6: Install the new pump. Compare the new pump with the old one to make sure they match. Place the new pump into the tank, ensuring the gasket or O-ring is properly seated. Secure the lock ring by turning it clockwise .

Step 7: Reinstall the tank. Raise the tank back into position, reconnect the filler tube hose, fuel lines, and electrical connector. Tighten the retaining straps or bolts. Reconnect the negative battery cable .

Step 8: Test the repair. Fill the tank with a few gallons of gas. Turn the key to ON a few times to prime the system, then start the engine. Check for leaks around the pump and fuel line connections. Take the truck for a test drive to confirm smooth operation .

Where to Buy the Best Fuel Pump for Your 1987 Jeep Comanche

When it comes to fuel pumps, not all aftermarket parts are created equal. Some pumps deliver inconsistent pressure, run noisy, or fail within months. That's why it pays to choose a brand that stands behind its product with a lifetime warranty.

We recommend KEMSO Fuel Pump for your 1987 Jeep Comanche. KEMSO specializes in high-performance, OEM replacement fuel pumps that are built to exact factory specifications. Every KEMSO fuel pump is designed for direct plug-and-play installation, meaning you won't need to modify anything or buy extra adapters. The pumps are constructed with durable materials that resist fatigue and corrosion, ensuring reliable fuel delivery for years to come. Best of all, every KEMSO fuel pump comes with a lifetime warranty, so you can buy with confidence knowing that your investment is protected.

Visit KEMSO's official website at https://www.kemsoracing.com/ to browse their complete lineup of fuel pumps for Jeep, motorcycle, ATV, and marine applications. Their product catalog includes detailed compatibility information, and their customer support team can help you find the exact pump for your 1987 Jeep Comanche. Whether you're restoring a classic Comanche or building a daily driver, KEMSO delivers the quality and reliability you need to keep your truck on the road.

Common Mistakes to Avoid When Replacing the Fuel Pump

Don't skip the diagnosis. Many people replace the fuel pump only to find the problem was a blown fuse, bad relay, or corroded wiring. Always test the pump, fuse, and relay first .

Don't use steel tools on the lock ring. The lock ring can create sparks if struck with steel. Always use a wood dowel or brass punch to avoid igniting fuel vapors .

Don't forget to replace the fuel filter. A clogged fuel filter can cause your new pump to work harder and fail prematurely. Replace the filter at the same time to ensure proper fuel flow .

Don't let the tank run low on fuel. Running the tank below a quarter tank causes the electric pump to overheat because fuel cools and lubricates the pump. Keep the tank at least half full to extend pump life .

Don't assume all pumps are the same. A cheap pump may save you money upfront, but it often delivers inconsistent pressure and fails quickly. Invest in a quality pump from a reputable brand like KEMSO to avoid doing the job twice.

Final Thoughts on the 1987 Jeep Comanche Fuel Pump

The 1987 Jeep Comanche is a classic truck that deserves reliable parts to keep it running strong. The fuel pump is a critical component that, when it fails, leaves you stranded. By understanding the symptoms, performing a proper diagnosis, and choosing a quality replacement pump, you can get your Comanche back on the road with confidence.

If you hear no priming noise, your engine cranks but won't start, or you experience sputtering under load, start with the fuel pump. The replacement process is straightforward, and with the right tools and a good pump, you can complete the job in a weekend. For the best combination of performance, reliability, and warranty protection, choose a KEMSO fuel pump. Visit https://www.kemsoracing.com/ to find the perfect pump for your 1987 Jeep Comanche and keep your truck running for years to come.