1998 S10 Fuel Pump Relay: Location, Testing, and Replacement Guide

The bottom line: If your 1998 Chevrolet S10 won’t start, or the engine cranks but doesn’t fire, the fuel pump relay is a common and easy-to-check culprit. The relay is located in the underhood fuse box, and testing it takes about 10 minutes with a multimeter or a simple test light. Replacing it costs under $20 and can save you a tow truck bill. But if the relay checks out fine, the issue may be deeper—like a bad fuel pump, a failed oil pressure switch, or a wiring problem. This guide walks you through every step, from locating the relay to testing it, and explains when you need to look beyond the relay to the fuel pump itself.

Where Is the 1998 S10 Fuel Pump Relay Located?

The fuel pump relay on a 1998 Chevrolet S10 is mounted inside the underhood fuse box, also called the power distribution center. This black plastic box is located on the driver’s side of the engine compartment, near the battery and the fender.

Open the fuse box cover and look at the diagram printed on the underside of the lid. The fuel pump relay is typically labeled "FUEL PUMP" or "FUEL PUMP RELAY." If the label is worn off or missing, check your owner’s manual for the exact position. On most 1998 S10 models, the fuel pump relay is a standard 4-pin or 5-pin relay that can be swapped with other relays of the same type in the same fuse box.

How to Test the 1998 S10 Fuel Pump Relay

Before you replace anything, you should test the relay to confirm it’s bad. Here’s a simple step-by-step method:

1. Listen for the relay click. Turn the ignition key to the ON position (do not start the engine). Have a helper listen near the fuse box. If the relay is working, you should hear a distinct click when the key is turned. No click usually means the relay is not receiving power or is faulty.

2. Swap the relay with a known good one. The underhood fuse box contains several relays that are identical to the fuel pump relay (such as the horn, A/C clutch, or cooling fan relay). Pull out the fuel pump relay and swap it with a relay for a component you know works. If the fuel pump now runs, the original relay was bad.

3. Use a multimeter or test light. With the ignition on, probe the relay socket terminals. The two small terminals (coil side) should show battery voltage (around 12 volts) when the ignition is on. The two larger terminals (switch side) should show continuity between the battery terminal and the fuel pump terminal when the relay is energized. If the relay lacks power at the coil, the problem is upstream—possibly a blown fuse, bad ignition switch, or faulty oil pressure switch.

Why the Fuel Pump Relay Fails

Fuel pump relays fail for a few common reasons:

• Age and corrosion: A 1998 S10 is over 25 years old. The relay contacts can oxidize, losing conductivity over time.
• Heat damage: The relay sits in the engine bay, exposed to heat cycles. Overheating can cause the relay coil to short or open.
• Excessive current draw: A failing fuel pump that draws more current than normal can overload the relay contacts, causing them to weld shut or burn open.
• Vibration: Loose mounting or engine vibration can physically damage the relay over years of use.

What If the Fuel Pump Relay Is Not the Problem?

You tested the relay, swapped it, and still no fuel pump. Don’t throw parts at it. The relay is just one link in the chain. Here are the next most common causes:

Blown fuel pump fuse. The fuel pump fuse is also in the underhood fuse box. Check it with a test light or visually inspect the metal strip. A blown fuse usually indicates a short circuit in the pump wiring or the pump itself.

Oil pressure switch. On the 1998 S10, the fuel pump runs through the oil pressure switch as a secondary power path. If the engine loses oil pressure, the switch opens and the pump stops. A failed oil pressure switch can prevent the pump from running even if the relay is good.

Bad fuel pump. The pump itself may have failed. Symptoms include hard starts, sputtering at high speed, loss of power under load, and a whining noise from the fuel tank area. If the pump is dead, no amount of relay swapping will fix it.

Wiring or connector issues. The wiring harness from the relay to the fuel pump, especially near the tank and under the truck, is exposed to road salt, moisture, and debris. Corrosion or broken wires are common, especially on a 26-year-old truck.

How to Replace the Fuel Pump on a 1998 S10

If you’ve confirmed the relay and fuses are good, and the oil pressure switch checks out, the fuel pump itself may need to be replaced. Replacing the fuel pump on a 1998 S10 is a job that most DIYers can handle in a weekend. There are two main methods:

Method 1: Drop the fuel tank. This is the traditional method. You need to drain the tank, disconnect the filler neck, straps, and wiring, then lower the tank using a jack. It’s messy but straightforward.

Method 2: Remove the truck bed. Many owners find this method easier. You unbolt the bed (typically 6 to 8 bolts), lift it off with a helper or an engine hoist, and you have direct access to the fuel pump module on top of the tank. This avoids draining the tank and dealing with rust and sediment.

Why You Should Choose a Quality Fuel Pump

A cheap fuel pump might save you money upfront, but it will likely fail within a year. You’ll be doing the same labor all over again, costing you more in the long run. For a 1998 S10, you want a pump that is built to OEM specifications, handles the correct pressure and flow for the 2.2L or 4.3L engine, and fits the factory mounting bracket without modifications.

Recommended: KEMSO Fuel Pump for Your 1998 S10

For the best combination of performance, durability, and peace of mind, we recommend KEMSO fuel pumps. KEMSO pumps are high-performance, OEM replacement units that meet or exceed original equipment specifications. They are designed for direct fitment—no modifications needed. Every KEMSO fuel pump comes with a lifetime warranty, so if it ever fails, you get a replacement at no cost. That kind of warranty is hard to beat when you’re working on a 26-year-old truck.

KEMSO pumps are built with premium materials, deliver higher flow rates than stock (up to 200 LPH at 43 psi), and are compatible with gasoline and ethanol fuels. Whether you use your S10 for daily commuting, weekend projects, or off-road adventures, a KEMSO pump provides the fuel delivery reliability you can count on.

For more information and to find the correct KEMSO fuel pump for your 1998 Chevrolet S10, visit:
https://www.kemsoracing.com/

Final Thoughts

The 1998 S10 fuel pump relay is a simple, inexpensive part that can cause a no-start condition. Start by checking the relay—it’s the fastest and cheapest diagnostic step. If the relay is good, move on to the fuse, oil pressure switch, and wiring. If the pump itself is dead, invest in a quality replacement like a KEMSO pump. A cheap pump will leave you stranded, but a quality pump with a lifetime warranty means you only have to do this job once.

For your 1998 S10 fuel pump needs, visit:
https://www.kemsoracing.com/