Having suffered with fuel problems of one sort or another over the last couple of years I decided to remove the tank and have a look inside to see if this was the cause of my problems and was it ever.
Amazingly everything undid fairly easily and the tank was quite easy to remove,having removed the 3 panels on the top of the tank it was apparent that 50 years of crap had built up on the inside specifically where the pickup pipe is situated.
Now my question is are all RML tanks the same mine is your normal looking tank but with a domed section where the drain plug is located,this seems to be a design fault as all the crap/water/that has found its way into the tank over many years settles at this lowest point and is then promptly sucked up the pickup pipe that takes its feed from this point.
Everything else seems to have been so well thought out on these buses,was this something that slipped through the net?
In a perfect world nothing should have found its way into the tank but sadly this is not a perfect world.

Graham

My bus number (if any): rml2478

My understanding is the dome (sump) is actually quick important, event my 2013 astra has one (just not so pronounce as the Routemasters one).

it is designed to collect water, which is why there is a drain, if you turn it (depending how good the seal is) approx half a turn it will drain any water out till diesel starts to come through. This is because water is denser then Oil and sinks to the bottem and get trapped in the sump.

As for dirt over a few (not 50) hardly any dirt should build up in the sump so shouldn't be a issue as the intake sits about 30mm from the bottom of the sump. Tanks in every vehicle where dirt can get in easily (a vehicle with a huge open fuel filler, unlike cars that have holes the same size as the hose) should be removed and cleaned periodically to prevent a large build up.

My tank was last serviced (as stamped on the tank) in 2003 i removed it at Christmas and was pleasantly surprised at how clean it actually was.

The other reason a sump is important, as the aforementioned inlet height above the bottom at 30mm in the sup accounts for approx 1 litre of diesel, if there was no sump and the inlet was 30mm from the flat base of the tank that 30mm could be at estimate 25 litres of diesel. This means you could "run out of diesel" on the side of the road with 25l diesel still in the tank, Crazy thought that!

Finally while running low on diesel with out a sump to trap diesel around the inlet. If you go down hill as the sump is toward the back of the tank, all the diesel will rush to the front of the tank could leave the inlet high and dry above the new diesel line causing a air lock in the system and in turn the engine stopping.

Hope this helps.

My bus number (if any): RMF2771

What Matt says is all good common sense. for years I had a problem on my GS with fuel starvation occasionally. Many years ago I'd had a new pipe made for in the tank, but the bus would appear to "run out of diesel" when stopping or cornering despite having about 3" of fuel in the tank.

About 4 years ago I decided tog et to the root of the problem so took out said "new" pipe, by now 30 years or more old and measured from the top of the outlet union to the bottom of the tank. there was about 25mm difference between that and the end of the pipe, sot I made a new pipe a bit longer and problem solved!

Now when the engine starts to die I KNOW it's about to run out of diesel! The reason tanks have baffles inside is to stop fuel sloshing about too much and causing fuel starvation as Matt says above.

My bus number (if any): RML2532