* Fuel Pump: The fuel pump might be weak or failing. It can't supply enough fuel at a consistent pressure to keep the engine running smoothly. Pumping the pedal momentarily increases the fuel pressure, enough to keep it going for a short time. This is a very common culprit.
* Fuel Filter: A clogged fuel filter restricts fuel flow. Pumping the pedal might momentarily overcome the restriction, allowing enough fuel to reach the engine.
* Pick-up Tube in Fuel Tank: The tube that draws fuel from the tank to the pump could be clogged with debris or have a crack. Similar to a clogged filter, pumping creates a surge that can temporarily overcome the blockage.
* Check Valve (in the fuel pump or fuel line): A faulty check valve allows fuel to flow back into the tank instead of staying under pressure in the line, leading to fuel starvation when the engine is idling or running at low RPM.
* Fuel Injectors (less likely, but possible): While less probable, problems with the injectors (clogged, leaking, low pressure) could contribute. However, usually injector problems would lead to rough running and misfires rather than only running when the pedal is pumped.
* Throttle Position Sensor (TPS): A faulty TPS can cause the engine to stall or run poorly, however this is less likely to only be a problem when the gas pedal is NOT pumped. The TPS is more likely to cause an issue at consistent throttle positions.
What to do:
1. Check the fuel pressure: This is the most important step. You'll need a fuel pressure gauge to measure the pressure. Low pressure confirms a fuel delivery issue.
2. Inspect the fuel filter: Replace it if it's dirty or old. It's a relatively inexpensive and easy fix.
3. Check the fuel pump relay: A bad relay can prevent the pump from working properly. Replacing the relay is a cheap and relatively simple attempt at a fix.
4. Listen for the fuel pump: Turn the key to the "on" position (without starting the engine). You should hear the pump briefly run. If you don't hear it, the pump may be faulty or the relay might be bad.
5. Consider a professional diagnosis: If you're not comfortable working on your fuel system, take it to a mechanic. They have the tools and expertise to diagnose the problem accurately.
Ignoring the problem could lead to further damage, especially if the fuel pump fails completely. Get it checked out as soon as possible.
