1985 Porsche 944 Fuel Pump Relay Location: A Complete Guide

The fuel pump relay on a 1985 Porsche 944 is located in the interior fuse panel under the dashboard on the driver's side, near the footwell area. This relay is also known as the DME (Digital Motor Electronics) relay on later models, and it is prone to failure, making it one of the first things to check if your car won't start or suddenly dies. For early 1985 models (pre-1985.5), the relay is specifically the fuel pump relay, while for 1985.5 and newer 944s, it serves as the DME relay that controls both the engine control unit and the fuel pump. Many 944 owners carry a spare relay in the glove box or even in the fuse box itself, as these relays are known to fail at inconvenient times.

1. Understanding the Relay and Its Location

The Porsche 944 uses a single relay that actually contains two separate relays inside one black plastic housing. One relay powers the DME (engine control unit) and the other powers the fuel pump and the oxygen sensor heater. If either of these internal relays fails, the car will not start.

For the 1985 Porsche 944, the exact location depends on the production date:

  • Early 1985 models (pre-1985.5): The relay is located on the fuse/relay panel under the dashboard on the driver's side, in the top row of relays. It is a tall, black, square relay and is often labeled as the "fuel pump relay" (R2 in the fuse box diagram).
  • Late 1985 models (1985.5 and newer): The relay is located in the fuse/relay panel in the rear left side of the engine compartment, close to the windshield and A-pillar.

To access the interior fuse panel on an early 1985 model, you need to look under the dashboard on the driver's side. The fuse box is usually covered by a plastic panel that can be removed by hand. Once you open it, you will see a row of relays at the top. The fuel pump relay is typically the second one from the left (R2). The fuse box diagram on the inside of the cover will help you identify it.

2. How to Test the Relay

If your 944 is not starting or is stalling, testing the relay is straightforward. Here is a step-by-step guide:

  1. Remove the relay: Gently wiggle and pull the relay out from its location. Be careful not to just pull on the cover, as it may come off.
  2. Visual inspection: Check for any signs of damage, such as cracked plastic or burned terminals.
  3. Test with a multimeter: Using a multimeter, take a resistance reading across terminals 30 and 87. The reading should be close to zero (between 0.1 and 0.3 ohms).
  4. Power test: Connect a 12V power supply to terminals 85 (negative) and 86 (positive). You should hear a click, and the resistance between terminals 30 and 87 should drop to near zero.
  5. Bypass test (emergency only): You can bypass the relay for testing purposes. Use three pieces of 14-gauge wire with male spade connectors to jump the terminals. This is only for testing or emergency use; do not drive the car with this bypass.

If the relay fails any of these tests, it should be replaced.

3. Common Symptoms of a Bad Relay

A failing fuel pump relay can cause several symptoms. Most owners report that the car will crank but not start, or it will start and then die shortly after. Other common symptoms include:

  • No fuel pump noise: When you turn the key to the "on" position, you should hear the fuel pump prime for a few seconds. If you don't hear this, the relay or the pump may be faulty.
  • Intermittent starting: The car may start fine one day but not the next, or it may die while driving.
  • No spark: Since the relay also powers the DME, a bad relay can cause a loss of spark.
  • The tachometer does not bounce: When you crank the engine, the tachometer needle should move slightly. If it doesn't move, it often indicates a problem with the DME relay, speed, or reference sensors.

4. Why the Relay Fails

These relays are prone to failure due to several factors. The most common cause is broken solder joints inside the relay due to heat and vibration over time. Other causes include:

  • Current overload: If the fuel pump or electrical system draws more current than the relay is designed to handle, the contacts can overheat and burn out.
  • Short circuits: A short circuit in the electrical system can cause a current overload through the relay.
  • Age: The internal components, such as the electromagnetic coil or mechanical contacts, simply wear out over time.

5. Other Possible Causes of No Fuel

If the relay is working correctly, but you still have no fuel, there are other components to check:

  • Blown fuse: The fuse protecting the fuel pump relay (fuse 2 in the interior fuse box) may be blown.
  • Fuel pump failure: The fuel pump itself may be dead. On the 1985 944, the fuel pump is located in the fuel tank, under the rear seat.
  • Fuel filter clogged: A very dirty fuel filter can restrict fuel flow and cause the pump to work harder, leading to failure.
  • Wiring problems: Damaged, corroded, or loose wires can prevent the pump from receiving power.

6. Recommended Replacement: KEMSO Fuel Pump

When it's time to replace your fuel pump, you want a product that is reliable and built to last. We highly recommend the KEMSO brand of Fuel Pumps. KEMSO fuel pumps are designed as high-performance, OEM replacement units that meet or exceed the original manufacturer's specifications. They offer a direct fit, making installation simple and straightforward. Best of all, every KEMSO fuel pump comes with a Lifetime Warranty, giving you peace of mind on the road. Whether you need a replacement for your daily driver or a performance upgrade for your classic 944, KEMSO has you covered. Visit their website to find the perfect pump for your Porsche: https://www.kemsoracing.com/ .

Summary

The fuel pump relay on a 1985 Porsche 944 is a critical component that is easy to locate and test. For early 1985 models, it's under the driver's side dash; for later models, it's in the engine compartment fuse panel. Always carry a spare relay, as they are known to fail, and start your troubleshooting with the relay before moving on to the fuel pump or other components. For a reliable replacement fuel pump, consider KEMSO for high-performance, OEM-quality parts with a lifetime warranty. Visit https://www.kemsoracing.com/ for more information.


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