Fixing a leak between the fuel tank and the fuel filler neck

you can buy the filler part for that 99 mercury mystique

Fuel Tank Filler Neck

when check engine light comes on VSC is disabled. small leak is for evaporative system (to prevent fuel vapors from entering the atmosphere) small leak is A leak less than forty thousandths of an inch, it could possibly be a gas cap not fully tightened,leak in a vapor line,leaking fuel filler neck,gas tank leak,purge valve,vent valve just to name afew. clearing code will turn off both lights but if theres a leak lights will come back on.

Replace your filler neck. It's not hard and when you buy the new one, installation should be obvious and rather straight forward.

A fuel leak is not something to take lightly and it will get worse over time.

Most fuel systems are pressurized (that's why you'll sometimes hear a hissing sound when you open your cap) so if your filler neck is leaking it can throw a code.

Removal & Installation To Remove:

1. Properly relieve the fuel system pressure.
2. Drain the fuel tank through the filler pipe.
3. Support the fuel tank.
4. Remove or disconnect the following:
   • Negative battery cable
   • Filler neck
   • Shield and tank straps
   • Fuel lines and vapor hose from pump and tank
   • Electrical connection from fuel pump
   • Fuel tank
   • Fuel pump/sending unit assembly by turning the locking ring (located on top of the fuel tank) counterclockwise using a spanner wrench
   • Fuel pump from the fuel lever sending device

To Install:

1. Install or connect the following:
   • Fuel pump in tank with new seal around opening
   • Tank and connect fuel lines and vapor hose
   • Tank to the frame
     1. Torque to: 33 ft. lbs. (45 Nm)
   • Shield
   • Fuel filler neck and clamp
   • Negative battery cable
2. Refill the tank.
3. Run the engine and check for leaks.

View of the in-tank fuel pump assembly.

filler neck may have hole in it

if it's a hose or pipe go to dealer or junk yard get another if broken clamp replace if neck part of tank call rad shop see if the can solder if you drain & pull tank

sounds like the fuel tank is building up pressure because of gas expansion. See if the fuel vent line is bent or kinked, if this is o.k change your fuel cap.

well you need to find out exactly where it is coming from . tank , line , filler neck , then we can break down the fixing from there .

Removal & Installation To Remove:

1. Properly relieve the fuel system pressure.
2. Drain the fuel tank through the filler pipe.
3. Support the fuel tank.
4. Remove or disconnect the following:
   • Negative battery cable
   • Filler neck
   • Shield and tank straps
   • Fuel lines and vapor hose from pump and tank
   • Electrical connection from fuel pump
   • Fuel tank
   • Fuel pump/sending unit assembly by turning the locking ring (located on top of the fuel tank) counterclockwise using a spanner wrench
   • Fuel pump from the fuel lever sending device

To Install:

1. Install or connect the following:
   • Fuel pump in tank with new seal around opening
   • Tank and connect fuel lines and vapor hose
   • Tank to the frame
     1. Torque to: 33 ft. lbs. (45 Nm)
   • Shield
   • Fuel filler neck and clamp
   • Negative battery cable
2. Refill the tank.
3. Run the engine and check for leaks.

Disconnect battery ground cable. Loosen fuel filler cap. Support underneath of the fuel tank protector Disconnect evaporative fuel hose at the canister. Disconnect fuel feed hose and fuel return hose near the fuel filter. Plug both ends of the fuel hoses to prevent fuel leakage. Disconnect air breather hose and fuel filler hose at the fuel filler neck. Cover fuel hose to prevent any dust entering. Remove the four fuel tank assembly fixing bolts at four corners of the tank. Let down the tank and disconnect the wiring connectors Remove fuel tank assembly along with protectors Remove retaining cover and roll over & float valve along with the evaporative fuel hose and pipe Remove fuel pump and sender assembly by removing the snap ring with the fuel hoses Remove protectors by removing the six fixing bolts