I received a lot of help with my 85 VdP from those here. Glad I could "give back" so quickly...Here is the procedure I used to drain the gas tanks...over-simplified. Be sure to disconnect the battery and 'de-pressurize' the fuel system (covered elsewhere).

1) The tanks have a draining 'bolt' on the bottom rear of the tanks. Accessing them is a problem, however. They are hidden under a black plastic cap (or 'bung'). See 1st photo.
2) The bung can be pushed up, but DOESN'T come out, unless you break it. What you need to do is remove the Phillips head screws along the bottom of the rear quarter panel with a #4 Phillips screwdriver. I sprayed WD-4 in between the panel skin near the screws to loosen it up a bit. See arrows on 1st photo.
3) Once the screws are out (pic 2 is of the screw) , you need to remove two 7/16th inch bolts in the wheel well (see 3rd & 4th photo). This allows you to pull the quarter panel enough away from the body to push the black bung cap up into the quarter panel and over to remove it (Pic 5). This should reveal the drain plug (see pic # 6 & 7).
4) Remove the drain plug with a 9/16ths socket, but NOT before making sure you have a container large enough to catch the fuel that is in the tank. Goes without saying gas (petrol) is flammable so be sure to do away from open flames, etc. Gas fumes can travel, so be sure to do far enough away from house as well (be careful in a garage if you have a hot water heater with a pilot light in there). I kept the fuel cap closed, but then opened it once I removed the drain bolt to make it drain faster. As my container was filling up, I closed the gas cap which slowed the flow a bit so I could put the drain bolt back in.
5) Make sure you look at the fuel as it comes out to see if there's rust, sludge, etc. If there is, reference some of the other posts on how to clean/seal the tank. I just poured 2 gallons new fuel in while drain open to remove any deposits, but I didn't have any sludge or rust.
6) Installation is reverse of above (as the Haynes manuals say) :-)

**NOTE There's supposed to be a screen of sorts, but apparently mine didn't have one..I guess just clean it and re-install, but can't say for sure as again I didn't have one.

 

1) you can use the jack's lugnut wrench to undo the tank bolts, it is the same size, especially if the bolts are impossibly tight, the wrench will give the leverage needed.

2) I have hole Caps that snap flush into the panel's hole, so I eliminated the inner "bung" altogether. In this way the hole remains covered and the cover or "cap" is removable.

Curiously, in the Series 3 XJ there are two size holes, one is the larger (1980-1985) and the smaller hole is found in the later cars (1986-1992).

 

Great info Jose, and great idea on the cap ! (#2) ~Dan

 

Mine didnt have the screen either...could have rusted away over the years.

 

• very helpful, found this in a google search - lugnut jack and away