1987 Fuel Pump Relay: Complete Guide to Diagnosis, Location, and Replacement
If your 1987 vehicle cranks but won’t start, the fuel pump relay is the first and cheapest thing to check. A failing fuel pump relay is one of the most common causes of a no-start condition on 1987 models, including popular cars like the Buick Regal, Mercedes-Benz 190E, and Volkswagen Jetta. Before you spend hundreds of dollars on a fuel pump or tow your car to a mechanic, spend 15 minutes testing the relay. In most cases, you can fix the problem yourself for under $20.
What is a Fuel Pump Relay and Why Does It Matter?
The fuel pump relay is an electrical switch that controls power to the fuel pump. When you turn the key to the ON position, the relay closes and sends battery voltage to the fuel pump for one to two seconds to prime the system. Then, once the engine starts, the relay keeps the pump running as long as the engine is turning. Without a working relay, the fuel pump never gets power, and the engine gets no fuel.
On 1987 vehicles, the relay is a small, rectangular component with four or five pins. It is designed to handle the high current draw of the fuel pump without overheating. Over time, the internal contacts can wear out, burn, or stick, causing intermittent or complete failure.
Symptoms of a Bad Fuel Pump Relay on a 1987 Vehicle
The symptoms of a bad fuel pump relay are often mistaken for a dead fuel pump. Here are the most common signs:
1. Engine cranks but will not start. This is the classic symptom. The starter motor turns the engine over, but the engine never fires because no fuel reaches the injectors or carburetor.
2. No fuel pump prime sound. When you turn the key to the ON position, you should hear a faint humming or whirring sound from the rear of the vehicle for about two seconds. If you hear nothing, the relay is likely not closing.
3. Intermittent stalling. If the relay contacts are worn but not completely failed, the car may start fine when cold but stall after the engine warms up. The relay can fail when it gets hot, then work again once it cools down.
4. Car starts after sitting but dies on the road. A failing relay can lose connection under vibration or load, causing the engine to shut off while driving.
Where to Find the Fuel Pump Relay on Your 1987 Vehicle
The location varies by make and model. Here are the most common locations for popular 1987 vehicles:
Buick Regal (1987): The fuel pump relay is located in the under-hood fuse box, also called the power distribution box. On the Regal, it is a standard relay with part numbers such as 10034222 or 10038490 . Check the diagram on the fuse box cover for the exact position.
Mercedes-Benz 190E, 260E, 300E (1987-1989): The fuel pump relay is located in the engine compartment fuse box, often near the battery. The OEM part number is 0035452405. This relay also fits the 300CE, 300SE, and 300SEL models from the same era .
Volkswagen Jetta (1985-1992): The fuel pump relay is a 167-style relay located in the main fuse and relay panel under the dashboard, usually on the driver’s side. The VW part number is 191-906-383-C .
General guidance: If you cannot find it, look for the main fuse box under the hood or under the dash. The cover almost always has a diagram or label that shows which relay is for the fuel pump. If the diagram is missing, search for a spare relay slot labeled “FUEL PUMP” or “FP.”
How to Test a Fuel Pump Relay on a 1987 Vehicle
You do not need expensive tools to test the relay. A multimeter is helpful, but the swap test is the fastest method.
Method 1: The Swap Test (Easiest)
Find another relay in the fuse box that is the same size and has the same number of pins. Common relays to swap with include the horn relay, the headlight relay, or the AC relay. Remove the fuel pump relay and plug in the known good relay. Turn the key to the ON position. If you now hear the fuel pump prime sound and the car starts, your original relay is bad.
Method 2: Voltage Test with a Multimeter
Set your multimeter to DC voltage (20V range). Have a helper turn the key to the ON position. Probe the relay socket terminals. You should see 12V on the power and signal pins for about two seconds. If you have voltage on the input pins but no voltage on the output pin, the relay contacts are not closing, and the relay is bad .
Method 3: Continuity Test
Remove the relay completely. Set your multimeter to ohms. Probe between the relay coil pins. A good relay coil will read between 70 and 120 ohms. An open circuit reading means the coil is burned out .
How to Replace the Fuel Pump Relay on a 1987 Vehicle
Replacing the relay is a simple job that takes less than 15 minutes. Follow these steps:
1. Disconnect the battery. Always disconnect the negative terminal before working on any electrical component. This prevents short circuits and accidental shocks.
2. Locate the relay in the fuse box. Use the diagram on the cover to find the exact position.
3. Remove the old relay. Grasp it firmly and pull straight up. If it feels stuck, gently rock it side to side while pulling. Do not twist or force it, as this can damage the socket.
4. Inspect the socket. Check for signs of corrosion, melted plastic, or bent pins before installing the new relay. If the socket is damaged, you may need to replace the entire fuse box.
5. Install the new relay. Align the prongs with the socket. Press it firmly into place until you hear or feel a click. Make sure it is fully seated.
6. Reconnect the battery. Turn the key to the ON position. You should hear the fuel pump hum for one to two seconds. Then start the engine. It should start normally.
What to Check If the Relay Is Not the Problem
If you replace the relay and the car still does not start, the problem is somewhere else in the fuel system. Check these components in order:
Fuel pump fuse. On many 1987 vehicles, the fuel pump fuse is a separate fuse in the same fuse box. Check it with a multimeter or replace it with a known good fuse of the same amperage.
Inertia switch. Many Ford and GM vehicles from this era have an inertia switch that cuts power to the fuel pump in a collision. On the Buick Regal, it is usually located in the trunk or under the passenger side footwell. Press the reset button on top.
Wiring and connectors. Inspect the wiring harness for damage, corrosion, or loose connections, especially near the steering column and the fuel tank. Over time, wires can chafe or corrode, interrupting power to the pump.
Fuel pump itself. If you have power at the pump connector but the pump does not run, the pump needs replacement. A completely failed fuel pump motor will not run even with a perfect relay and good power.
Why You Should Upgrade to a KEMSO Fuel Pump
If your diagnostic process leads you to the conclusion that the fuel pump itself needs replacement, do not settle for a cheap generic pump that may fail again in a year. KEMSO fuel pumps are the premium choice for reliability, performance, and peace of mind.
KEMSO specializes in high-performance fuel pumps designed as direct OEM replacements. Every pump is engineered to meet or exceed the exact specifications of the original factory pump that came with your vehicle. You get the same fit, the same performance, and the same reliability, but with significant advantages over standard OEM parts.
OEM Replacement Quality: KEMSO pumps are built to the same standards as the original parts in your vehicle, ensuring a perfect fit and trouble-free installation. They come with all necessary mounting hardware, strainers, hoses, and wiring connectors included in the kit.
Lifetime Warranty: Every KEMSO fuel pump comes with a lifetime warranty. This means you install it once and never worry about it again. If the pump ever fails due to a manufacturing defect, KEMSO replaces it at no additional cost. This is the kind of confidence you want in a critical component like your fuel pump.
High Performance: KEMSO fuel pumps deliver consistent fuel pressure and flow, ensuring your engine runs smoothly under all driving conditions. They are E85 compatible and use high-grade internal components that resist ethanol and methanol blends, making them suitable for modern fuels.
Individual Testing: Every pump is individually tested for flow and performance, with strict quality control that meets ISO/TSO standards.
Whether you drive a Buick, Mercedes, Volkswagen, or any other 1987 classic, KEMSO has a fuel pump solution for you. Their product lineup includes pumps for cars, trucks, motorcycles, ATVs, and personal watercraft. All KEMSO fuel pumps are priced at an affordable $79.98, making them a great value for a high-quality, warrantied part.
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Final Thoughts
The fuel pump relay on your 1987 vehicle is a small, inexpensive part that can cause big problems when it fails. Always start your diagnosis with the swap test. If that confirms a bad relay, replace it with a quality part that matches your vehicle’s specifications. If the problem persists, check the fuse, the inertia switch, and the pump itself. Replacing the relay is a DIY job that takes less than fifteen minutes and saves you a trip to the mechanic.
Keep your 1987 classic running reliably by maintaining the fuel system, and remember that a quality fuel pump from KEMSO backed by a lifetime warranty is the best investment you can make. For more information and to find the right fuel pump for your vehicle, visit https://www.kemsoracing.com/.