Fuel filler cap recess drain

Good evening everybody,

as I currently have my rear quarter panels taken off the car I wanted to make use of the occasion to check whether the fuel filler recess drains are functional. I tested them with water and high pressure air. The good news is that the left one which was blocked freed up with pressurized air. A lot of black rubbish was blown out of the rubber tube.

The bad thing is that on the right hand drain where the water drained easily I didn’t get any air blowing out the tubes at the bottom (yes, the quarter panels are currently removed). Cross-checking I found that one of the rubber tubes taking down to the end of the drain has been attached by mistake to the front vent pipe at the filler cap recesses, meaning that the water in the recess pours through the lower and rearward facing opening directly into the wing and causes rust, as there’s no tube attached, while the forward facing opening with the rubber tube draining down will never be reached by the water level … duhhh

My sense of order, but also my penchant for properly functioning systems are utterly disturbed. The problem is that I shy away from a complete removal of the tank just to reattach the tube correctly to the rearward facing drain pipe. Even without the quarter panel it seems you would need an arm no thicker than an inch, but equipped with no less than 8 3D-elbows and able to exercise sufficient pressure at the end to press on some piece of rubber tube …

Frankly, I don’t expect an easy fix - it’s just that I didn’t want to miss the chance to get this one right before reassembly. Maybe someone has made experience with blocking the rearfacing drain and using only the frontfacing drain: is the drain hole low enough to work or will water get inside the tank before the drain hole actually drains?

Thanks in advance for any suggestion!


75 XJ6L 4.2 auto (UK spec)


I’m a bit confused here…
Yours is an SII that I’m not familiar with, but AFAIK, the hose (C.33043) that attaches to the fuel filler cap is connected to the carbon canister. It vents fuel as the opening is bellow the fuel cap rubber.
Does the SII have a fuel vapour recovery system?

The rear recess water drain has a much bigger tube that goes all the way down behind the rear wheel arch.
How can one mix those two is beyond me…

As it should…!


Ser 2 US versions do, UK and Euro (and possibly ROW, perhaps not a few countries) do not.

My 1975 XJ6C vents the fuel tanks to the atmosphere via small holes in the filler neck and has a rubber tube (on each side) running down on the inner wing to a small hole in the bottom if the body, just as the water drains do. The water drain hoses have a couple of T-joints which are prone to develop blockages as the rear screen to trunk area with the interior air exit vent box is also drained through the same hoses / tubes.


The two ‘drains’ have entirely different purposes, Jochen…

One vents water from the filler cap recess, and obviously does so with or without hose attached - with drawbacks you mentioned without the hose. The other is the tank’s vent hose, letting air in and out of the tank, and must on no(!!) account be blocked!

As Aristides says; with the closed tank ventilation system, the vent hose connects, through the fuel separators in the C-pillar, to the charcoal canister. On ‘European’, and possibly early US cars, when closed tank ventilation was not used, a hose from the tank vent just went down below the car - venting tanks while minimizing fuel smells. All of which works perfectly for tank venting - but may be contrary to emission control regulations

Whether attaching the drain hose is worth while to avoid water from the filler cap recess causing rust problems is arguable. With proper paint and external tank protection, there should not really be a problem. However, it might be possible to fit a drain hose by removing the filler cap assembly…?

xj6 85 Sov Europe (UK/NZ)