1. Verify Fuel Delivery:
* Fuel Pressure: This is crucial. Use a fuel pressure gauge to measure the fuel pressure at the TBI fuel rail. You need the correct specification for your engine (check your owner's manual or a reliable online resource). The pressure should remain consistent at idle and under load (at half-throttle). A drop in pressure under load indicates a problem, even with a new pump. Check pressure both with the engine running and after it cuts out.
* Fuel Filter: A clogged fuel filter can restrict fuel flow, especially under higher demand. Replace it – it's cheap and easy. A clogged filter could have damaged the new pump.
2. Ignition System:
* Distributor Cap and Rotor: Inspect for cracks, corrosion, or worn contacts. Replace if necessary. These are common wear points and can cause intermittent issues.
* Spark Plugs and Wires: Check the spark plugs for proper gap and condition. Worn or fouled plugs can cause misfires, especially under load. Inspect the spark plug wires for cracks or damage.
* Ignition Coil: A failing ignition coil can also cause power loss, particularly under stress.
3. Throttle Body/Throttle Position Sensor (TPS):
* Throttle Body Cleaning: Clean the throttle body thoroughly with throttle body cleaner. A dirty throttle body can affect airflow and fuel delivery.
* TPS Testing: The TPS tells the computer the throttle position. A faulty TPS can cause erratic fuel delivery and power loss. You'll need a multimeter to test its voltage output. There are many online guides for testing a TPS specific to your vehicle.
4. Mass Airflow Sensor (MAF):
* MAF Sensor Cleaning: A dirty MAF sensor can also lead to poor fuel delivery. Clean it carefully with MAF sensor cleaner (do not use anything else).
5. Computer/ECM:
* Codes: Check for diagnostic trouble codes (DTCs). Your vehicle should have a diagnostic port you can connect a scanner or code reader to. This will provide valuable clues about the problem. An auto parts store may scan it for free.
6. Vacuum Leaks:
* Inspection: Carefully inspect all vacuum lines for cracks, leaks, or loose connections. A leak can disrupt the fuel/air mixture and cause power loss.
7. Fuel Injectors:
* Testing (Advanced): If all else fails, the fuel injectors could be clogged or faulty. Testing injectors requires specialized tools, but a failing injector is a possible cause.
Important Considerations:
* Fuel Pump Installation: Make sure the fuel pump was installed correctly, with proper grounding and connections. A wiring error could be the culprit.
* Relay Replacement: Ensure the new relay is the correct type and is properly installed.
Troubleshooting Steps:
Start with the easiest and cheapest fixes (fuel filter, cleaning the throttle body and MAF sensor, checking spark plugs and wires). Then, move to the more involved checks (fuel pressure, TPS, codes). If you're not comfortable working on your vehicle's electrical or fuel systems, take it to a qualified mechanic. Ignoring a fuel-related problem can lead to more extensive and costly damage.
