* Injector Pump itself: The most likely culprit is a leak within the injector pump itself. These pumps are complex and can develop internal seals or gasket failures that lead to fuel weeping. This often manifests as a slow leak from the bottom or sides of the pump. This is a major repair, often requiring pump rebuild or replacement.
* Fuel Supply Line to the Pump: While you've checked the banjo bolts at the pump's inlet, there could be a leak further back along the supply line leading to the pump. This line might have a crack, a loose fitting, or a deteriorated rubber section. Carefully examine this entire line, paying close attention to connections and potential points of wear.
* Return Line from the Injectors: The fuel return lines from the injectors eventually collect and return fuel to the tank. While less likely to cause a significant leak *under* the pump, a major failure in this system *could* cause a large amount of fuel to pool in that area. Inspect these lines for cracks, leaks, or loose connections. A leak higher up the return system might drip down and collect at the rear of the pump.
* Cracked Fuel Housing (Less Likely): The fuel pump housing itself might have a crack. This is less common but possible, especially if the truck has seen significant vibration or damage.
Troubleshooting Steps:
1. Clean the area thoroughly: Use a degreaser to clean the area around the injector pump. This will allow you to pinpoint the exact source of the leak. Let it dry completely.
2. Visual Inspection (Again): With the area clean and dry, carefully examine *everything* around the injector pump. Use a flashlight and a mirror to get into hard-to-see areas. Look closely at all connections, lines, and the pump housing itself.
3. Pressure Test (If Possible): If you have the tools and expertise, consider pressurizing the fuel system. This can help isolate whether the leak is in the supply or return system. Warning: Be extremely cautious when pressurizing a diesel fuel system. Diesel fuel is flammable.
4. Professional Help: Given the complexity of the 7.3L fuel system and the potential for serious damage, it's strongly recommended you take your truck to a qualified diesel mechanic. Diagnosing and repairing a fuel leak on a diesel engine requires specialized knowledge and tools. Continuing to drive with a fuel leak can lead to fire hazards, engine damage, and environmental contamination.
Do not attempt repairs unless you have significant experience working on diesel fuel systems. Diesel fuel is highly flammable, and incorrect repair attempts can be dangerous. Safety should be your top priority.
