Mustang Fuel Tank Kit (1965-1968) Installation Instructions

Mustang Fuel Tank Kit Install Image
Mustang Fuel Tank Kit Install Image
1. To begin installation of your Mustang Fuel Tank Kit, make sure the car is off and has had ample time for the engine, tail pipes and muffler to cool down. They should all be cool to the touch before beginning. Disconnect the battery. Make sure the work area is well ventilated, with fresh, outside air. Also, make sure any heaters, open flames or electric devices that could start and cause a spark are turned off. Chock the front wheels to prevent the car from rolling, while raising the rear of the vehicle. Chocks should be used in front of and behind the front wheel.
Mustang Fuel Tank Kit Install Image
2. Raise the back of the vehicle and rest it on jack stands. Make sure you use a jack and jack stands that are rated for the weight of your vehicle.
Mustang Fuel Tank Kit Install Image
3. You can raise the rear of the vehicle by placing a block of wood on the jack and placing it under the pumpkin of the Mustang rear differential.
Mustang Fuel Tank Kit Install Image
4. Position the jack stands under the rear axle, between the wheel and the pumpkin on each side.
5. Start by draining any remaining fuel from the tank. It is best to plan ahead and run the fuel down, as low as possible, before attempting to replace the tank. Otherwise, you need to make sure you have gas cans to hold up to 16 gallons of gas.

There are three ways in which to drain the tank, which is important for installation of Mustang fuel tank kits.
  • a. If you have a drain plug, this is the most convenient way to drain the fuel. The drain plug is located on the bottom corner of the tank, on the passenger side, close to the shocks.
    1. - The drain plug should come out with a 3/8" wrench.
    2. - Turn the wrench counter-clockwise.
    3. - It is very common for the drain plug to be fused into the tank. If it will not turn, you will have to use another method.
Mustang Fuel Tank Kit Install Image
Mustang Fuel Tank Kit Install Image
  • b. Siphon the gas from the tank through the filler pipe. I recommend getting a siphon to accomplish this.
Mustang Fuel Tank Kit Install Image
  • c. The last resort is to drain the fuel from the back of the tank. You can remove the rubber hose that connects the sending unit to the fuel line. Be prepared to collect the fuel as it leaks out. You must also be very careful not to get fuel on the muffler.
Mustang Fuel Tank Kit Install Image
Mustang Fuel Tank Kit Install Image
6. Once the tank is drained, disconnect the wire from the fuel line to the sending unit and the hose that connects the sending unit (if it wasn't already disconnected in a previous step).
Mustang Fuel Tank Kit Install Image
7. Remove the gas cap by turning it counter-clockwise.
Mustang Fuel Tank Kit Install Image
8. After removing the gas cap, you gain access to the screws that hold the filler pipe. Begin by removing the 4 filler pipe screws with a 5/16" socket.
Mustang Fuel Tank Kit Install Image
9. The gas cap is secured to the vehicle by a steel cable. This was used to prevent the gas cap from being stolen. This needs to be removed in order for the Mustang fuel tank filler pipe to be removed.
10. This is also a good time to inspect the gas cap gasket and replace if it shows signs of wear or if you smell gas fumes while it is attached. I think mine will have to be replaced.
Mustang Fuel Tank Kit Install Image
11. In order to remove the gas cap retainer cable, there is a nut that needs to be removed from within the trunk. This will require a 7/16" socket. The best way to access this is straight on, just below the filler pipe, with an extension attached to the socket.
Mustang Fuel Tank Kit Install Image
12. Loosen the clamps on the Mustang filler pipe hose and pull the filler pipe out through the taillight panel, from the back of the vehicle.
13. There are 12 bolts that hold the tank in. 11 of them can be removed with a 3/8" socket. There is one bolt that is removed with a 1/2" socket. This bolt is also used to secure one of the brackets for the rear bumper.
Mustang Fuel Tank Kit Install Image
14. To lift the tank out of the trunk, you can position the jack under the tank, and with a block of wood between the jack and the tank, jack it up.
15. In order to remove the sending unit, the retainer ring needs to be removed. The best way to do this is to use a regular screw driver. There are studs around the inner ring that are to be used to turn the ring counter-clockwise and remove the sending unit. Take great care not to damage the fuel gauge stud or fuel tube when removing the retainer ring.
Mustang Fuel Tank Kit Install Image
16. Take care removing the Mustang C8ZZ-9275-CR fuel sending unit from the tank. Once removed, inspect it for damage and wear. Replace the sending unit if it is worn, damaged or you do not get an accurate reading on the fuel gauge.
Mustang Fuel Tank Kit Install Image
17. Check the filter screen and make sure it is not deteriorating or has clogging due to debris in the tank.
Mustang Fuel Tank Kit Install Image
18. Check the Mustang fuel sending unit float and make sure it is solid and working. If there are any holes or advanced corrosion, it will need to be replaced.
Mustang Fuel Tank Kit Install Image
19. Before we can install our new fuel tank, all contact surfaces must be cleaned and inspected. All edges of the trunk area should be inspected for rust and corrosion. If any metal is in need of repair, patching or replacing, it should be done now.
Mustang Fuel Tank Kit Install Image
20. All old caulking cord should be scraped out and the metal surface cleaned.
Mustang Fuel Tank Kit Install Image
21. If the old tank is being reused, this too should be thoroughly cleaned and inspected around the edges.
Mustang Fuel Tank Kit Install Image
22. The sending unit is held in the tank by a Mustang COAZ9A307B fuel sending unit retainer ring and sealed with a rubber gasket. The gasket fits between the tank and the back of the sending unit. The gasket fits in a grooved ring on the tank.
Mustang Fuel Tank Kit Install Image
23. The gasket is round.
Mustang Fuel Tank Kit Install Image
24. The sides of the gasket are not round, but rather, rectangular, as shown.
Mustang Fuel Tank Kit Install Image
25. The gasket will stand on end, in the groove, to seal properly.
Mustang Fuel Tank Kit Install Image
26. When inserting the sending unit, it will only seat in the tank in one position. There are two notches in the tank opening, as pictured above. The sending unit has tabs that fit in the notches, as shown below.
Mustang Fuel Tank Kit Install Image
27. With the gasket in place, insert the sending unit by putting the float in first.
Mustang Fuel Tank Kit Install Image
28. Then carefully insert the filter end. Be careful not to snag the filter on the notches in the tank. These can be sharp and can rip the filter, diminishing it's effectiveness.
Mustang Fuel Tank Kit Install Image
29. Now that the sending unit is in, make sure the gasket has not moved. It should still be seated in the groove and not protruding into the tank or out past the sending unit.
Mustang Fuel Tank Kit Install Image
30. Attach the retainer ring and tighten it in place, using a regular screw driver and turning in a clockwise direction, using the studs on the retainer ring. You may have to apply a little pressure to the sending unit and compress the gasket to get the retainer ring started.
Mustang Fuel Tank Kit Install Image
31. Keep rotating until the tab on the retainer ring seats in the notch on the tank. This secures the retainer ring in place.
Tip: A sending unit can be replaced without removing the tank. The problem you have is getting the gasket properly lined up and kept in place as you tighten the retainer ring. My experience has been that it is far easier to remove the tank when replacing the sending unit, especially if you don't have a lift for your vehicle.
Mustang Fuel Tank Kit Install Image
32. Now that the sending unit is installed, it is time to put the Mustang fuel tank back in. If you had removed the drain plug to drain the fuel, make sure you have properly re-installed it.

Begin by placing Mustang flexible strip caulk around the edge of the tank. The caulking cord prevents metal to metal contact between the trunk edge and the tank. This also holds the tank in position and seals out any moisture that may try to get up under the tank lip.
Mustang Fuel Tank Kit Install Image
Mustang Fuel Tank Kit Install Image
33. Position your jack under where the tank will seat. Raise the jack and put a block of wood on it. Next, rest the tank in the trunk, on top of the block of wood, on the jack. This way you can lower the tank in slowly and make sure that everything lines up. Once the caulking cord makes contact, it starts to stick.

After the tank is in position, re-install the 11 screws with a 3/8" socket and the one bolt, with a 1/2" socket.
Mustang Fuel Tank Kit Install Image
34. Now that the tank is in and secured, you can attach the filler pipe. Place the filler pipe hose on the tank and put both clamps loosely around the hose, resting on top of the tank.
Mustang Fuel Tank Kit Install Image
35. Place a piece of caulking cord around the top of the filler pipe neck, wrapping it tightly around where the neck and flange attach.
Mustang Fuel Tank Kit Install Image
36. Place the cork gasket onto the filler pipe up to the flange.
37. Place the filler pipe through the back of the taillight panel and insert into the filler pipe hose.
38. Attach the filler pipe with the 5/16" screws.
39. Attach the gas cap retainer cable and secure from within the trunk, with the 7/16" nut.
40. Tighten the clamps on the filler pipe hose, where it attaches to the gas tank and the filler pipe.
41. Before final tightening of the screws and clamps, test fit the gas cap to make sure it is straight. The slots in the filler pipe allow you to adjust the final resting place of the gas cap. When finished it should look like this:
Mustang Fuel Tank Kit Install Image
42. Connect the sending unit to the fuel line, by installing the rubber hose between them. I always recommend using a new hose, when doing this. Clamp them down tight. Attach the fuel gauge wire.
Mustang Fuel Tank Kit Install Image
43. Tighten all screws, bolts and clamps to factory specifications.
44. Probably one of the most important things to do is test your seals and check for leaks. Just make sure that you have enough containers handy, that if you start to leak and have to drain the tank, you can store the fuel. If you only have 1-2 cans and make several trips to the gas station, you could have a problem if you have to reseal something.
45. Start by putting about 1-2 gallons of gas, in the tank.
46. First, check the drain plug for leaks, since this is the lowest point in the tank.
47. If no leaks are observed, add another 2-3 gallons of gas.
48. Carefully inspect the sending unit, checking the hose between the sending unit and the fuel line as well as the gasket around the sending unit.
49. If still no leaks, add another 2-3 gallons or make sure the tank is at least 1/2 full at this point.
50. Making the tank 1/2 full will make sure that the sending unit is submerged and you can check for leaks all around the gasket.
51. Let the vehicle sit for about an hour or two, checking for leaks periodically. If you still have no leaks, reconnect the battery and take it for a quick test drive.
52. I usually like to let the car sit overnight and check for leaks in the morning. If all is still good, fill the tank up, but again, check for leaks.
53. Enjoy the experience of installing your new Mustang Fuel Tank Kit!