Fuel Pump Delivery Rate – Checking -2.5L NA

Overview

This procedure checks the fuel pump delivery rate on the Porsche 944 (8-valve engine) to ensure it meets the required specifications. Proper fuel delivery is critical for engine performance and efficiency. This guide applies to both pre-1985.5 and 1985.5 onwards variants, with model-specific steps clearly marked.

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Tools Required

• Metric Wrench Set
• Measuring Container (1500 ml / 50 fluid ounces or larger)
• Hose (to connect to the fuel pressure regulator)
• Hose Clamp
• Stopwatch or Timing Device
• Catch Rags

Step-by-Step Procedure

Step 1: Prepare for Fuel Line Disconnection

1. Place catch rags around the fuel pressure regulator (FPR) to absorb any fuel that may spray during disconnection, as the fuel rail may be under high pressure.

Step 2: Disconnect the Fuel Return Line

2. Slowly disconnect the return line from the fuel pressure regulator (FPR) that leads back to the fuel tank to prevent fuel spray.
3. Using a hose clamp, attach a hose to the discharge port of the FPR. Ensure the hose is long enough to reach the measuring container.

Step 3: Remove the Appropriate Relay

4. Remove the relay based on your model year:

For Pre-85.5 models:
Locate and remove the fuel pump relay under the dashboard on the driver’s side (for right-hand drive vehicles, check the passenger side).

For 85.5 Onwards models:
Locate and remove the DME relay on the fuse/relay panel under the hood.

Step 4: Jumper the Relay Terminals

5. Locate terminals 30 and 87b on the relay panel where the relay was removed. Check the terminal number labels on the bottom of the removed relay if unsure.
6. Jumper terminals 30 and 87b to activate the fuel pump. Be ready to start the stopwatch as the pump will begin running immediately.
7. Start the stopwatch as soon as you hear the fuel pump running.

Step 5: Measure the Fuel Delivery

8. Allow the fuel pump to run for exactly 30 seconds, collecting fuel in the measuring container.
9. After 30 seconds, remove the jumper to stop the pump.
10. Measure the amount of fuel in the container and compare it to the specifications below:

• Most fuel pumps: 850 ml (28.7 fluid ounces) in 30 seconds.

• Pumps with green paint code (0 580 464 028): 750 ml (25.4 fluid ounces) in 30 seconds.

Step 6: Evaluate the Results

11. If the measured fuel volume is significantly below the specified values, inspect the fuel pump, fuel filter, or fuel dampener for potential issues.

Post Procedure Checklist

• Ensure all fuel lines are securely reconnected to the fuel pressure regulator.
• Check for fuel leaks around the FPR and hose connections.
• Verify the relay (fuel pump relay or DME relay) is reinstalled correctly.
• Dispose of any spilled fuel and used rags safely.
• Confirm the measured fuel delivery meets or exceeds the specifications for your fuel pump type.

Sources

• Clark’s Garage
• Pelican Parts
• Porsche 944 Workshop Manuals
• YouTube