FSJ Fuel Sock / Sending Unit Replacement

This article details the replacement of the fuel sock and/or sending unit for a Full Size Jeep. The vehicle in this article is an 83 Jeep Cherokee owned by John Clark of the Colorado Full Size Jeep Association. This is a good example because this particular vehicle has never before had this done so I was able to detail the removal of the stock rivets attaching the access plate. You should do this in a very well ventilated area and leave the doors open as well as the tailgate. There will be fuel vapors so do not under any circumstances use an electric vacuum, smoke, or in any other way create a spark or have an open flame.

You will need the following tools:
T-50 Torx bit (most likely 3/8" drive)
1/2" Breaker bar or large ratchet
1/2" to 3/8" socket adapter
Drill
1/8" to 3/16" drill bit
#2 Phillips Screw Driver
Medium Flat Screwdriver
Side Cutters
Large Channel-Lock Pliers
Medium Length Needle-Nose Pliers
Medium Hammer (~2 lb.)
Wooden or Plastic stick (~1/4" diameter)
Compressed air (from compressor or several dusting cans)

Supplies Needed:
3 small hose clamps
RTV Black or Silicone Sealant
4 #10 x 3/8" sheet metal screws

Click on any picture for a larger view
This (or something similar) is what you start with. You will want to fold the rear seat forwards in order to access the access panel. If you have a Wagoneer or 4 door Cherokee you can get to the access panel through the rear drivers side door. First remove all the trim pieces that are screwed down through the carpet and into the floor. There should be 2 screws in each trim strip. You then need to remove the rear seat belts. The bolt will require a T-50 Torx bit, and probably a 1/2" breaker bar as shown. They will be very tight and may be rusted as well. You can spray some penetrating oil on the bolts from the bottom of the Jeep.
After removing the rear seat belts, make sure the rear area is empty to you can roll back the carpet. Under the carpet you should/may find a cardboard liner as shown. You only need to roll back the carpet far enough to remove the forward half of this cardboard liner, it is in two sections. After you remove the cardboard liner, you should see a round cover plate toward the front of the rear floor area and on the drivers side.
If the access panel has never been removed before it should look like this, if it is held down with screws insead of rivets then it has been accessed before. Using a drill with a 1/8" to 3/16" bit, carefully drill down the center of each rivet just until the head of the rivet is loose (it will probably stick to the bit and spin with it). Originally the cover is sealed to the floor with a pretty tough sealant. You will need to use a medium flat screwdriver and hammer to get break the seal. Carefully go all the way around the plate only prying slightly up at each point so you don't bend the cover. If you do bend the cover, it is fairly easy to straighten.
Once you get the cover off you will likely find lots of dirt and possibly some fuel staining. If you smell fuel vapor at this point, you probably have a bad hose as well which should be replaced. If you need to replace the fuel lines, you may need to drop the fuel tank to do it. You will need to clean out the dirt. Loosen the caked dirt with a wooden or plastic stick. Use compressed air to blow the dirt away from the sending unit. DO NOT USE AN ELECTRIC VACUUM - IT COULD CAUSE AN EXPLOSION. At this point you need to be very careful about any type of spark or ignition source as there are going to be fuel vapors around. Remove the two wires from the sending unit. You may find it easier to use a pair of medium length needle-nose pliers for this job. After removing the wires, you can tape them to the floor away from the hole if they seem to be getting in your way.
Notice that one of the 3 hoses is not in a very friendly location. Unless you need to remove this hose from the tank because you are replacing it, just leave it be, it can be moved out of the way. Here I have tucked the 3rd hose out of the way by carefully rolling it between the body and the gas tank. Don't force it in there with a screwdriver or you may puncture or otherwise damage the hose. Notice the factory clamps on the fuel lines, these must be cut off with a set of side cuters to be removed. Remove the hoses and tuck, tape, or otherwise hold them out of the way. Don't loose them down the channel in the fuel tank where they are routed though. Use a large set of Channel-Lock pliers to gently unscrew the sending unit retaining nut. You may want to use compressed air again prior to this to clean out any additional dirt.
Once the retaining nut is removed you will want to clean the area again with compressed air. You want as little dirt as possible to fall int the tank when you remove the sending unit. You can now gently lift up the sending unit to remove it. Note the float in the picture, be very careful not to loose this off the end of the fuel sensing rod (especially if you are not replacing the sending unit), because you will never retrive it again. Also be very careful not to permanently bend the sensing rod while removing the unit, you will need to flex it a bit but don't actually bend it. Notice the difference between the old and new fuel sock. The original sock is black where as the new one will be white, but the old one will likely be clogged or disentigrated as well. Be sure to note the orientation of the sock on the pickup tube (not only location, but rotation as well). This is important for correct fuel pickup abilities.
Note the orientation of the new fuel sock. You will need to use the side cutters to remove the original clamp holding the sock onto the pickup tube. Use a standard hose clamp to attech the new sock to the pickup tube. The new sock is clamped onto the pickup tube, and the unit is ready to be re-installed. There is a rubber o-ring that seals the sending unit to the tank. Remove this o-ring and thoroughly clean it (unless you are replacing it with a new sending unit. Also clean the area again with compressed air to remove any dirt that is still left. If you are re-using the old o-ring you may want to put a very light coating of vaseline on it depending on it's condition.
Re-Install the sending unit in the reverse order that you removed it in. Be careful not to loose the float, don't damage the hoses, use new hose clamps. Again, be careful during this process as there are fuel vapors present. Before replacing the cover, run a thin bead of RTV or Silicone sealant around the opening to re-seal the cover preventing any potential fuel vapors from entering the vehicle later on. Use 4 #10 x 3/8" sheet metal screws to re-attach the cover plate. Check the length of your screws before installing the cover, if they are too long they will penetrate the fuel tank. Tighten the screws and allow some time for the sealant to cure before replacing the carpet.
Replace the cardboard liner, making sure the extra pieces on the bottom line up with the ridges in the floor. Roll the carpet back out and re-attach to the floor where necessary. Re-Attach the seat belts, making sure the bolts are tight and secure.
Smoothe out the carpet so the trim strips will lay back out nicely, and do a double check to make sure you did not leave any tools behiend. Re-Attach the trim strips and you are back to where you started, but with a new fuel sock, sending unit, or both.


Return to JTruck.net Technical Section