Here are some possible culprits:
* Fuel pressure regulator: The most likely cause. When the engine runs, the fuel pump builds pressure. A faulty fuel pressure regulator could be releasing excess pressure, pushing fuel past a seal or connection. The leak location above the tank points to a potential failure at the regulator, particularly if it's located near the tank, which is common on some vehicles.
* Fuel injectors: A less likely possibility, but a faulty injector could leak fuel under pressure when the engine runs. However, this is more likely to result in drips near the engine, rather than above the tank.
* Fuel line connection: The fuel pump replacement might have inadvertently loosened or damaged a fuel line connection. A clamp not tightened properly or a damaged line could leak under pressure. Double-check all connections near the tank.
* Incorrect fuel pump installation: While less likely if it was installed by a professional, an improper fuel pump installation could inadvertently cause pressure issues leading to a leak.
* Pressure sensor: A faulty fuel pressure sensor could indirectly cause a problem, but the leak itself would likely still be due to a faulty regulator or line.
What you should absolutely NOT do:
* Do not drive the vehicle. Driving with a gas leak is extremely dangerous due to the risk of fire.
What you MUST do:
* Have a qualified mechanic inspect the vehicle immediately. This is not a DIY job. The risk of fire is too high. They have the specialized tools and knowledge to diagnose and repair the fuel system leak safely.
* Describe the problem completely to the mechanic. Be precise about when the leak occurs (only when the engine is running), where it's leaking (above the tank), and the fact that a fuel pump was recently replaced. This helps them pinpoint the source more quickly.
Ignoring this could have devastating consequences. Address this immediately for your safety.
