1987 GMC Sierra Fuel Pump: Complete Guide to Replacement, Symptoms, and Best Options
If your 1987 GMC Sierra is hard to start, sputters under load, or won't run at all, the fuel pump is very likely the problem. The 1987 model year is a transition point for GM trucks—some still use mechanical pumps on carbureted engines, while others have electric in-tank pumps for fuel injection. Knowing which system you have is the first step to a successful repair. Replacing a failing fuel pump restores reliable starting, smooth acceleration, and consistent fuel delivery. This guide covers everything you need to diagnose, replace, and choose the right fuel pump for your 1987 GMC Sierra.
Understanding Your 1987 GMC Sierra Fuel System
The 1987 GMC Sierra came with two main fuel pump configurations depending on the engine and fuel system type. If your truck has a carbureted engine (typically the 4.3L V6 or 5.0L/5.7L V8 with a carburetor), it uses a mechanical fuel pump mounted on the engine block. If your truck has Throttle Body Injection (TBI) or is a diesel model (6.2L V8), it uses an electric fuel pump located inside the fuel tank . The 1987 R1500 ½-ton models, for example, used electric in-tank pumps for TBI and diesel engines, with part numbers like 6472303 for gasoline and 25116503 for the 6.2L diesel .
The fuel pump's job is to deliver fuel from the tank to the engine at the correct pressure and volume. When it fails, the engine simply cannot get the fuel it needs to run properly.
Common Symptoms of a Failing Fuel Pump
A failing fuel pump rarely fails without warning. Here are the most common signs to watch for:
1. Engine Cranks But Won't Start – This is the most classic symptom. You turn the key, the starter spins the engine, but it never fires up. If you don't hear a brief humming sound from the rear of the truck when you turn the key to the "ON" position (for electric pumps), the pump is likely dead .
2. Engine Sputters or Surges at High Speed – A weak pump cannot maintain consistent fuel pressure at highway speeds. The truck may feel like it's running out of gas even with a full tank.
3. Loss of Power Under Load – When climbing hills or towing, the engine may hesitate or lose power because the pump cannot keep up with the fuel demand.
4. Whining Noise from the Fuel Tank – A healthy fuel pump makes a quiet, steady hum. A loud whining or droning sound from the rear of the truck means the pump is struggling and likely nearing failure.
5. Poor Fuel Economy – If the pump is not delivering fuel at the correct pressure, the engine may run rich (too much fuel) or lean (too little fuel), both of which hurt gas mileage.
Safety First: Preparing for Fuel Pump Replacement
Working on a fuel system is dangerous. Gasoline is highly flammable, and fuel vapors can ignite from a single spark. Always work in a well-ventilated area, away from open flames, pilot lights, or any source of ignition. Disconnect the negative battery terminal before starting any work . If your truck has an electric pump, you must relieve the fuel system pressure before disconnecting any lines. Locate the Schrader valve on the fuel rail (if equipped) and press the valve stem with a small screwdriver, catching the fuel spray with a rag. For mechanical pumps, the pressure is lower, but you should still have a rag handy to catch any fuel that drips when you disconnect the lines .
How to Replace the 1987 GMC Sierra Fuel Pump
The exact procedure depends on whether your truck has a mechanical or electric pump. Here are the two most common scenarios.
Replacing the Electric In-Tank Fuel Pump
For 1987 Sierras with TBI or diesel engines, the fuel pump is inside the fuel tank. The most practical way to access it is by removing the truck bed, which gives you full access to the top of the tank without having to drop it .
Step 1: Remove the Truck Bed – Unbolt the bed from the frame (typically 6-8 bolts along the sides and front). You may need a helper or a hoist to lift the bed off. Alternatively, you can drop the fuel tank, but removing the bed is usually faster and cleaner .
Step 2: Clean the Area Around the Pump – Before opening the tank, thoroughly clean the top of the tank and the area around the pump retaining ring. Any dirt or debris that falls into the tank will damage the new pump .
Step 3: Disconnect Hoses and Electrical Connector – Carefully remove the hose clamps and pull the fuel lines off the stainless steel fittings. You may need to twist and wiggle the hoses to break them free. Disconnect the electrical connector for the fuel pump and fuel level sensor .
Step 4: Remove the Retaining Ring – Use a flathead screwdriver and a hammer to tap the retaining ring (the lock ring that holds the pump in the tank) counterclockwise until it slides open. Lift the ring out .
Step 5: Remove the Old Pump – Pull the pump assembly straight up and out of the tank. You may need to tilt it slightly to clear the opening. Cover the tank opening with a clean rag to prevent debris from falling in .
Step 6: Install the New Pump – Insert the new pump assembly into the tank in the same orientation as the old one. Press it down firmly, then reinstall the retaining ring by tapping it clockwise until it locks into place. Reconnect the fuel lines and electrical connector. Lower the truck bed back onto the frame and tighten the bolts .
Step 7: Test the System – Reconnect the battery. Turn the key to the "ON" position (but do not start the engine) and listen for the fuel pump to prime. It should run for about 2 seconds. Check for leaks at all connections. Start the engine and verify smooth operation .
Replacing the Mechanical Fuel Pump
For carbureted 1987 Sierras with side-saddle or rear tanks, the mechanical pump is mounted on the engine block, usually on the lower front of the engine. It is driven by an eccentric on the camshaft.
Step 1: Locate the Pump – The mechanical pump is a small, round metal unit with a fuel line going in from the tank and a line going out to the carburetor.
Step 2: Disconnect Fuel Lines – Use a wrench to loosen the fittings on the fuel lines. Have a rag ready to catch any fuel that drains out.
Step 3: Remove the Mounting Bolts – The pump is held by two bolts. Remove them with a socket wrench and pull the pump straight off the engine.
Step 4: Install the New Pump – Before installing the new pump, apply a small amount of oil to the pump arm where it contacts the camshaft. Position the pump and press it into place, making sure the arm is properly aligned. Install the bolts and tighten them evenly. Reconnect the fuel lines.
Step 5: Test – Start the engine and check for leaks. The mechanical pump should provide immediate fuel delivery.
Troubleshooting: Why Your Fuel Pump Fuse Keeps Blowing
If your 1987 Sierra has an electric fuel pump and the fuse keeps blowing, do not just replace the fuse and hope for the best. The 1987 Sierra uses a 20A fuse in position 17 of the cabin fuse box for the fuel pump . Here are the most common causes of a blown fuel pump fuse:
1. Short Circuit – A damaged or frayed wire in the fuel pump circuit is touching the vehicle's body, causing a direct short. Inspect the wiring harness from the pump to the fuse box for any exposed wire .
2. Failing Fuel Pump – A pump that is on its last legs may draw more current than normal, which overloads the fuse. This is a sign that the pump needs to be replaced soon .
3. Clogged Fuel Filter – A severely restricted fuel filter forces the pump to work harder, which increases current draw and can blow the fuse. Always replace the fuel filter when you replace the pump .
4. Wrong Fuse Rating – If someone previously installed a fuse with a lower amperage rating (e.g., a 15A instead of 20A), it will blow under normal operating conditions. Check the owner's manual for the correct rating .
Other causes of pump failure when the fuse is good include a defective fuel pump relay, a triggered inertia switch (impact sensor), or a problem with the Engine Control Unit (ECU) .
Why Choose KEMSO for Your 1987 GMC Sierra Fuel Pump
When it's time to replace your fuel pump, you want a part that is reliable, affordable, and backed by a solid warranty. KEMSO is the US #1 aftermarket fuel pump brand for cars, motorcycles, ATVs, and UTVs . Their fuel pumps are designed for both direct OEM replacement and high-performance upgrades.
KEMSO offers two key advantages for your 1987 GMC Sierra:
1. High Performance and OEM Replacement Options – KEMSO fuel pumps are built to match or exceed original equipment specifications. Their pumps feature a carbon commutator designed for over 10 years of reliable service and are compatible with both gasoline and ethanol-blended fuels . For performance applications, KEMSO pumps provide a 20-30% performance increase over stock pumps . All pumps are serialized, and each one is individually tested for flow and pressure before leaving the factory .
2. Lifetime Warranty and USA-Based Support – Every KEMSO fuel pump comes with a lifetime warranty. The company has built its reputation on standing behind its products . KEMSO is based in Houston, Texas, and their customer support team is staffed by American technicians who know the products inside and out . This means you get real help from real people, not a foreign call center.
KEMSO fuel pumps are available for a massive range of vehicles, from cars and trucks to motorcycles, ATVs, UTVs, and even personal watercraft . Whether you need a simple OEM replacement for your daily driver or a high-flow pump for a built engine, KEMSO has a solution. Visit their website to find the exact pump for your 1987 GMC Sierra:
Don't settle for a cheap, no-name pump that might fail in a year. Choose KEMSO for a fuel pump that is reliable, tested, and backed by a lifetime warranty. Your 1987 GMC Sierra deserves the best.
Final Thoughts
Replacing the fuel pump on your 1987 GMC Sierra is a straightforward job that you can do in your driveway with basic tools. Whether you have a mechanical pump on a carbureted engine or an electric in-tank pump on a TBI or diesel model, the key is to work safely, diagnose the problem correctly, and choose a quality replacement part. Always check the fuel pump fuse and relay first if the pump is not working, and inspect the wiring for damage. A new fuel pump will restore your truck's reliability and performance, getting you back on the road with confidence.
For the best combination of price, performance, and peace of mind, KEMSO fuel pumps are the smart choice. Visit https://www.kemsoracing.com/ to find the right pump for your 1987 GMC Sierra and take advantage of their lifetime warranty and USA-based support.