1991 Fuel Pump Relay: The Complete Guide to Location, Diagnosis, and Replacement
If your 1991 car cranks but won't start, the fuel pump relay is one of the first things you should check. This small but critical component controls power to the fuel pump, and when it fails, your engine gets no fuel. The good news is that finding, testing, and replacing a 1991 fuel pump relay is something most DIYers can handle with basic tools and a little know-how. This guide covers where to find the relay on popular 1991 models, how to test it, and what to do when it's time for a replacement.
Understanding the 1991 Fuel Pump Relay
The fuel pump relay acts as a switch that sends battery power to the fuel pump when you turn the ignition key. On most 1991 vehicles, the relay is a standard Bosch-style 4- or 5-pin unit that sits inside a fuse or relay box . When you turn the key to the ON position, the relay clicks and powers the pump for about two seconds to prime the fuel system. If you don't hear that brief hum from the fuel tank area, the relay or its circuit is likely the problem.
The relay itself is an electromagnetic switch. A small current flows through a coil inside the relay, which pulls a set of contacts together to complete the high-current circuit to the fuel pump. Over time, the contacts can burn, the coil can fail, or corrosion can prevent proper connections .
Where to Find the Fuel Pump Relay on 1991 Models
The location varies widely by make and model. Here are the most common locations for popular 1991 vehicles:
Ford Mustang (1991): Under the driver's seat. This is an unusual location compared to most cars, but Ford specifically placed it there on 1991 models .
Ford Ranger (1991): Under the hood in the relay box on the driver's side, near the firewall. The box is rectangular and black plastic. Look for a relay labeled "FUEL PUMP" or "FP" .
Ford Taurus / Mercury Sable (1991): No separate relay exists. The fuel pump relay is built into the Integrated Control Relay Module, which mounts on the radiator support at the front of the engine bay .
Mercury Capri (1991): In the engine bay fuse and relay box. The lid diagram typically labels a "FUEL PUMP" relay position .
Volvo 760, 940, 960 (1991): The relay is a green colored unit often located in the engine bay fuse box. Part number 1362914 is the OEM replacement for these models .
Volkswagen Jetta (1991): Two possible locations. The interior fuse box (Type 1) contains a fuel pump relay in position R2. The interior fuse box (Type 2) has a 20A fuse for the fuel pump in position 18 .
Saturn SC / SL2 (1991): In the engine bay fuse box. The relay is a multiuse part (OEM number 19118886) that also fits other Saturn models from 1991-2002 .
Jaguar XJ40 / XJ6 (1991): Two locations depending on the build date. Earlier 1990 models have it under the passenger side dash. For 1991 models, the relay moved to the left side of the engine bay, above the brake pedal housing on left-hand drive cars. Look for a yellow base relay .
Chevrolet Corvette (1991): Under the passenger side dash, behind the plastic hush panel near the floor courtesy light. It is the middle relay in a panel of five relays mounted on the dash frame .
Mercedes-Benz 190E (1991): There is no separate fuel pump relay. The fuel pump is controlled through the MAS (Main Auxiliary Systems) relay. Jumping pins 1 and 2 on the MAS relay will run the pump directly .
How to Test the Fuel Pump Relay
Before you buy a new relay, confirm the old one is actually bad. Here is a simple step-by-step test:
1. Listen for the prime. Turn the ignition key to the ON position (do not crank the engine). Listen near the fuel tank or the rear of the car. You should hear the fuel pump run for 2-5 seconds and then shut off. If you hear nothing, the relay may not be closing .
2. Check for a click. With the key in the ON position, place your hand on the relay or listen closely. You should feel or hear a single click when the relay energizes. No click means the relay coil is not getting power or has failed .
3. Swap with a known good relay. Most cars use the same relay for multiple circuits (horn, fog lights, etc.). Find an identical relay in the fuse box, swap it with the fuel pump relay, and see if the pump starts working .
4. Use a test light or multimeter. Back-probe the fuel pump connector at the tank to check for 12V when the key is turned ON. If voltage is present but the pump does not run, the pump itself is bad. If no voltage is present, the relay or its wiring is the issue .
5. Jump the relay socket. Remove the relay and use a jump wire to connect the power and load terminals in the socket (usually pins 30 and 87). If the pump runs, the relay is bad. If the pump still does not run, the problem is elsewhere in the circuit .
Common Causes of Fuel Pump Relay Failure
Fuel pump relays fail for several reasons, and understanding these can help you prevent future problems:
Current overload. If the fuel pump draws more current than the relay is designed to handle, the contacts overheat and burn out. This often happens when an old fuel pump begins to fail and draws excessive current .
Short circuit. A short in the fuel pump wiring or in the pump itself can cause a sudden current spike that destroys the relay contacts or burns the coil .
Age and wear. The internal components of a relay degrade over time. The electromagnetic coil can weaken, and the mechanical contacts can develop pitting or carbon buildup from repeated arcing .
Corrosion. Water intrusion into the relay socket or fuse box is a common problem. On some models, water leaks from the windshield or antenna can cause corrosion that prevents the relay from making good contact .
Vibration damage. Relays mounted in areas subject to constant vibration can develop internal fractures or loose connections over time.
What Else Can Cause a No-Fuel Condition?
If the relay tests good but the pump still does not run, check these components before assuming the pump is bad:
Blown fuse. The fuse that protects the fuel pump circuit or the relay itself may be blown. Check the fuse box and replace any blown fuses .
Inertia switch (Ford vehicles). Many Ford cars and trucks have an inertia switch that cuts power to the fuel pump in a collision. On 1991 Ford Taurus and Mercury Sable, this switch is located in the trunk on the left side above the wheel arch. Press the reset button to check if it has tripped . On 1991 Ford Mustang hatchbacks, the inertia switch is under the plastic trim on the driver's side near the taillight .
Oil pressure switch (GM vehicles). On 1991 Corvettes and many other GM cars, the oil pressure switch provides a backup power path to the fuel pump. If the relay fails, the pump will still run once oil pressure reaches 4 psi, but the engine will require longer cranking to start .
Fuse links. In the engine bay, fuse links (short wires designed to act as fuses) can burn out. Check the fuse link near the starter relay or battery. On Ford Mustangs, a blown fuse link in the pink/black wire will kill power to the fuel pump relay .
Wiring harness damage. Wires can chafe, corrode, or break, especially in areas exposed to road salt, moisture, or heat. Check the wiring from the relay to the pump, particularly where it passes through the floor or under the rear seat .
How to Replace the Fuel Pump Relay
Replacing a 1991 fuel pump relay is straightforward. Follow these steps:
1. Locate the relay. Use the information above to find the relay on your specific vehicle.
2. Remove the old relay. Grasp the relay firmly and pull it straight out of the socket. Some relays may have a small retaining clip.
3. Inspect the socket. Look for corrosion, melted plastic, or burnt pins. Clean the socket contacts with electrical contact cleaner if needed.
4. Install the new relay. Push the new relay firmly into the socket until it seats fully.
5. Test the system. Turn the ignition to ON and listen for the fuel pump prime sound. If the pump runs, the replacement was successful.
When to Replace the Fuel Pump Instead of Just the Relay
Sometimes the relay is fine, and the pump itself has failed. Here are signs that point to a bad fuel pump rather than a relay:
- The pump runs when you jump the relay socket, but the car still has low fuel pressure or no pressure at the fuel rail
- You hear the pump running but the car struggles to start or stalls under load
- The fuel filter is clogged, which can cause the pump to work harder and fail
- The pump makes unusual noises like whining or grinding
If the pump itself is the problem, replacing it with a high-quality unit is essential for long-term reliability.
Why Choosing the Right Fuel Pump Matters
A failing fuel pump can leave you stranded, and a cheap replacement may fail again in a short time. When you need a replacement fuel pump, quality counts. That is why we recommend KEMSO Fuel Pumps.
KEMSO offers high-performance fuel pumps that are direct OEM replacements. Every KEMSO fuel pump is built to meet or exceed original equipment specifications, ensuring a perfect fit and reliable operation. Whether you drive a car, truck, motorcycle, or personal watercraft, KEMSO has a fuel pump designed for your application.
What sets KEMSO apart:
- High-performance construction – Designed to handle the demands of modern engines
- OEM replacement quality – Direct fit, no modifications needed
- Lifetime warranty – KEMSO stands behind every pump with a lifetime warranty, giving you peace of mind
Visit https://www.kemsoracing.com/ to browse their full selection of fuel pumps for cars, trucks, motorcycles, ATVs, and watercraft. With competitive pricing and a lifetime warranty, KEMSO is the smart choice for your fuel system needs.
Quick Troubleshooting Guide for 1991 Vehicles
If your car cranks but will not start, follow this checklist:
1. Turn the key to ON and listen for the fuel pump. No sound? Proceed to step 2.
2. Check the fuel pump relay. Locate it, listen for a click, and swap it with a known good relay if possible.
3. Check the inertia switch (if equipped). Press the reset button.
4. Check the fuse. Look for a blown fuel pump fuse in the fuse box.
5. Jump the relay socket. If the pump runs with the relay bypassed, replace the relay. If the pump still does not run, check for power at the pump connector.
6. Test for voltage at the pump. If you have 12V at the pump but it does not run, the pump is bad. If no voltage, trace the wiring back toward the relay.
7. Replace the pump if needed. If you confirm the pump is bad, install a quality replacement like KEMSO.
Final Thoughts
The 1991 fuel pump relay is a small part that can cause big headaches. Knowing where to find it, how to test it, and what else to check can save you time and money. Start with the simple tests, use the information in this guide for your specific vehicle, and replace components with quality parts. A systematic approach will get your car running again quickly.
For reliable fuel pump replacements, remember KEMSO Racing at https://www.kemsoracing.com/ – your source for high-performance, OEM-quality fuel pumps backed by a lifetime warranty.