RRC fuel tank breather pipe

Just had a really good weekend green laneing in the RRC in wales with
just two epics!. Unfortunately I have got a blocked fuel tank breather
tube… On opening the cap (with some difficulty) there is now a great
in take of air.

It's an H Reg, metal tank, with the fuel pump that bolts into the top
of the tank. Can anyone tell me where the breather starts and where it
should end? In fact can anyone give me a summary of all the pipes on
the tank?

In <[email protected]> chaintong wrote:
> Just had a really good weekend green laneing in the RRC in wales with
> just two epics!. Unfortunately I have got a blocked fuel tank breather
> tube… On opening the cap (with some difficulty) there is now a great
> in take of air.
>
> It's an H Reg, metal tank, with the fuel pump that bolts into the top
> of the tank. Can anyone tell me where the breather starts and where it
> should end? In fact can anyone give me a summary of all the pipes on
> the tank?
>

You should have a multi-vent tank so I'll start with that assumption...
there is some variation from year to year but the following is a typical
arrangement.

If you were to view the tank from the top, with the filler pipe on the
RHS there are 6 pipes (plus the filler) coming from the tank.

The largest of the 5, enters the tank near the filler, is the breather
that is used to allow air out when you are filling up. This goes up to
the top of the filler pipe. At this point there is another small pipe
that goes to the catch tank and is used to feed any fuel in the catch
tank back to the fuel tank.

The three small pipes that exit the tank above the filler are the normal
vent pipes. In most cases these go to a joiner and are combined into a
single pipe. I've never been convinced of the need to have 3 pipes but
internal to the tank these pipes go to 3 different areas of the tank.
The output from the joined pipes goes to the catch tank where air coming
in is filtered from fuel and vapour going out. (On some arangements
these small pipes aren't joined but go direct to the catch tank)

The pipe furthest away from the filler on the same side is the fuel
return pipe taking "spare" fuel from the pressure regulator on the fuel
rail, internally this pipe runs straight down to the swirl pot that the
fuel pump sits in.

The fuel supply comes from the last pipe which goes straight to the fuel
pump on the top of the tank.

The air intake for the catch tank (and through that the air intake for
the fuel tank) loops up into the wing and exits at the bottom of the
wing near the rear bumper.

cheers

Dave W.
http://www.yorkshireoffroadclub.net/

Dave,

That looks plenty of info to sort it:

But since I am at work just another couple of questions (for clarity)

-1- I have never noticed a catch tank... what does it look like, do
they all have one.
-2- Can I get at these pipes without dropping the tank.

Finally, this is the first time the rangie has been in some real deep
muddy water, is the standard design adequate or do people modify the
air intake to a higher location?

Tom

In <[email protected]> spamtrap_
[email protected] wrote:
> Dave,
>
> That looks plenty of info to sort it:
>
> But since I am at work just another couple of questions (for clarity)
>
> -1- I have never noticed a catch tank... what does it look like, do
> they all have one.

Most late classics have them. They sit between the inner and outer rear
wing, only visible if you remove the wing. They are about a foot long, a
foot high and about an inch thick AFAICR. This is certainly the
arrangement on late 1980s, early 1990s models that I have had apart. On
Discovery and Defenders they moved to a charcoal canister system located
under the bonnet that releases excess fuel into the engine. The
principal is the same but the canister replaces the catch tank. It is
possible that they did the same with the RR but I've not owned one from
that era.

Both systems are designed to prevent petrol vapour escaping to the
atmosphere. A great idea if your a Californian Tree Hugger but they do
add uneccessary complexity to the system.

> -2- Can I get at these pipes without dropping the tank.

You probably only need to clear the intake pipe, the end of which is
easily accessible, poke your head up inside the wing behind the wheel
and you should be able to spot the pipe coming down the inside of the
outer wing near the back of the wing. All the pipes are accessible
without dropping the tank although the catch tank is pretty inaccessible.

> > Finally, this is the first time the rangie has been in some real
> > deep
> muddy water, is the standard design adequate or do people modify the
> air intake to a higher location?

The following may answer that question....
http://www.yorkshireoffroadclub.net/gallery/muddy_truckers/

On my fuel tanks, since that occasion, I have modified the air flow of
the tank to ensure that it can't happen again. The best way to do this
is to "borrow" the valves from the catch tank. One of these valves opens
when the tank is in vacuum, the other opens when the tank is at pressure.
Alternatively you can buy the valves from the later carbon canister
system.

If they aren't joined already, join the three vent pipes together then
use a Y connector to split the vent back to two pipes. Attach one of the
pipes to the positive pressure valve and the other to the vacuum valve.
Route the inlet pipe to the vacuum valve as high as possible and the
outlet pipe to the positive pressure valve as low as possible.

Using this system means that the tank will normally be pressurised
slightly or at vaccum depending on the fuel level and amount of gas
being released from the fuel. Even if water did get into the inlet, the
valve would prevent any syphoning effect from occurring.

I have transferred this design onto my current competition vehicle and
haven't experienced any problems with it.

cheers

Dave W.
http://www.yorkshireoffroadclub.net/