Leaking fuel line under engine - 2000 Ford F350 Super Duty Super Cab

Fuel leaks are diagnosed by pressurizing the fuel system and inspecting for the leak source. The fuel system can be pressurized by simply cycling the ignition key to the ON position; the fuel pump will come on for about three seconds to "prime" the lines, then turn off. The pressure will remain on the fuel in the lines so inspection can begin. Fuel leaks in the engine bay can originate from fuel lines, the fuel rail or fuel injectors. If the origin of the leak is not visible, it may be necessary to remove certain engine components to gain the necessary access. I find it helpful to locate the fuel injectors first, then follow the rail to the lines and keep working rearwards until the source is located. You can read more about fuel system leaks here: https://www.yourmechanic.com/article/symptoms-of-bad-or-failing-fuel-injection-lines

Well, you need a quick tutorial on your fuel system. Now to find a leak, stop trying to start the engine. You are only adding electrical charge to an already dangerous situation. Now stop and think this through. Modern fuel injection requires fuel under high pressure to operate. The injectors are immersed in this pressurized gas, as are the lines leading to them from the fuel tank's fuel supply line. So just by turning the key to ON, not start, you have initiated the process to start the engine, and that means the pump has operated for 2 seconds to put the fuel system under high pressure.

Now if you follow the fuel supply line (from the gas tank) to the engine connection, start here to find a leak. It is now under high pressure from here to the injectors on the engine- one for each cylinder-it should be dripping with gas somewhere. You could even turn the key to off after the pump has ran for 2 seconds. The fuel system is designed to hold pressure in the system for about 10 to 15 minutes, before slowly bleeding off. Enough time to search for a gas leak. A couple of other things associated with the system: there will be also a fuel return line from the injector rail, it goes back into the gas tank. both the supply line and the return line often run alongside each other. There is also a fuel pressure regulator, immersed in the fuel rail, a seal on that may have started leaking. If an air breather housing, or some cover prevents your seeing the fuel system entirely, then set it aside. You should be able to find the leak. Just be careful, have lots of rags handy, happy hands are learning hands.

rusted gas line

check under the hood for any leaks from the fuel line, which comes up in front of the firewall and then turns back toward the engine. from the rear.
This could be a vacuum line leaking to the exhaust canister, it could be a leak near the fuel tank or filler coming from a vapor recovery line that goes to the engine compartment. Check the trunk to see if it has that smell. If so, check for a vacuum line under the car and see if it is unhooked and/or cracked. (does the smell get worse after you've filled the tank?) If so, this may be the culprit.
Replace these lines as necessary.

Good luck.

engine hard to start smelling fuel first look under hood for signs leaking fuel lines if you raise hood get strong gas smell look for wet fuel leaks on top engine where fuel lines located.if see no leaks could have leak at fuel rails to fuel injectors.if see no leaks look under vechicle around fuel tank area look for fuel dripping.

LOOK UNDER THE HOOD AROUND THE ENGINE FUEL LINES LEADING TO FUEL RAILS FOR PETROL LEAKS AND LOOK UNDER CAR AROUND FUEL TANK AREA.LOOK FOR LEAKS AT FUEL LINES.REASON VECHICLE NOT STARTING FUEL LEAK TAKING AWAY FUEL PRESSURE.FUEL LEAK HAVE TO BE AT THE FUEL PUMP FUEL LINES OR YOUR FUEL INJECTORS OR FUEL RAIL HAS A FUEL LEAKS AT THE O - RINGS.

SMELL GAS YOU NEED CHECK ALL FUEL LINES UNDER THE HOOD IN THE ENGINE COMPARTMENT.IF GAS IS STRONG UNDER HOOD YOU DONT SEE LEAKING FUEL LINES.YOUR FUEL RAIL FUEL INJECTORS LEAKING OR FUEL PRESSURE REGULATOR O - RING OR DIAPHRAM LEAKING GAS.IF FIND NO LEAKS UNDER THE HOOD CHECK FUEL LINES UNDER CAR FROM ENGINE TO FUEL TANK FOR LEAKS.IF ALL IS GOOD YOUR EVAPORATIVE CANISTER SOAKED WITH GAS OR YOUR EMISSION EVAPORATIVE SYSTEM NOT WORKING. DEALERSHIP HAS TO CHECK AND FIX.

If the engine is running ok it will be a return line,or a leaking injection line,Has your engine been worked on before on the top end if and line has been bent in the past it is proned to leak,I hope this helps

It sounds like the return fuel line is leaking. There are two fuel line and one is the high pressure line which goes to the fuel pressure regulator then to the fuel rails. There is then a return line from the fuel rail to the gas tank.
With the amount of fuel leak, it's going to be the return line since it's not that bad compared to the high pressure side. Follow the fuel lines from the drivers side around the steering shaft to the engine. The high side and low side (return) run side by side and you should see it leaking when the engine is running.
Good luck and hope this helps.