white90 Posted October 16, 2005 Share Posted October 16, 2005 Hi all, When I found out that the 90s tank was leaking (Oh deepest joy -it does low enough MPG as it is ) I also decided to take the opportunity to convert the appalling petrol cap to something that would allow the fuel to stay as fuel, and not have it 'joined' by muddy water, which could be so easily done, the cap is not high up at all.... The 90s tank cap I had was the early one, like a series 'domed cap' with a bayonet type fitting to the filler, with what can only be described as a drill hole in the center of the cap, .....not very clever for any wading, and as the 90s cap is quite low, not difficult to shove in the gooo..the later caps are similar, .....bit better but still rubbish IMHO. Hopefully this will give you some ideas... 1st having fitted new tank (what a PITFA job that is ) I took the opportunity to remove all the filler, pipework and hoses etc, The some work and filling later saw this fiited in its place...., it came from "Think Automotice" at Isleworth, .... Yes I know....bit bling but a beautifully made peice of kit.....and this is a 'non vented' unit. This comes in 2 parts, a 'non vented cap', (either locking or non locking - I chose locking), and a mount, the one which is known a 'FUN2' would be 2.25 inch same as the filler neck on a later 90 hose, mine being an early type had a 3" neck, so I lathed up an adapter, and tig welded it to the connector. All fitted it now looks now like this... Now...... as the std cap is vented (read drilled hole at factory FFS.....), I had to make up a unit to allow : 1. Fuel vapour to exit on filling tank (the small 1/2 pipe top of the tank, and 2. also a venting system as cap and therefore system non vented This was achived by this, ..............a piece of 2.25 inch tube, with a 3/8 Hyd hose connector cut of and welded on (my gas welding is not that good, lack of practise so don't start !), and similar for the fuel hose to tank from a 1/2 Hyd connector, .................all welded togther gives this : Then all I did was take the std hose, cut in the right place and add the unit I had made, then drilled a hole up through the wheel box fit grommet and shove some pipe down through it and connect to the unit, at the cab end I fiited a TRV (think autonmotive) Roll Over Valve, and then dropped some 3/8 clear hose back down through the wheel box (another grommet) and vented the fuel vapours into as handy chassis hole. Then I conected the 1/2 hose to the unit and tank, these 2 pics just about show how it then look jubilee clipped up : AS I said a "Mini- Tech" type of article, but so useful to have a Fuel cap that is 100% waterproof as opposed to the factory junk...thought it might be of interest? Nige Hi Nige excuse my ignorance, but why does it need to be vented? Cheers Steve --------------------------------------------------------------------- hbyrid, excellent work! but to get the filller cap 100% watertight you are still missing one step. I've got two of these filler caps for my sill tanks in the rear wheel arches. when i tested them putting the car at an angle, i realized that they are leaking fuel. they are not tight after all. the same happened when i pressure tested the tanks, the filler caps let the air out. the rubber o ring is too small, either geth a thicker one or take some ptfe string that is used for sealing threads and wrap it around the metal were the o ring sits. smear some fuel resistant sealant on that and put the o ring back on. now it is watertight! regards spec ---------------------------------------------------------------------- Take a plastic drinks bottle, warm it up so the air inside is nice and warm (sit it on a radiator for a bit), and then put the cap on. Put it in a sink full of cold water. It will be "a little smaller" once the air inside has cooled down - the same thing will happen to an unvented fuel tank, and even more so if there is a 4.5 litre Eales sucking hard on one end as well I have seen a RR with a blocked vent pipe and the fuel tank only held about 30 litres after it had collapsed! ------------------------------------------------------------------------ Just asked as it seems latest tanks on p38 and l322 RR are not vented as there is always a pressure differential when the cap is undone. Cheers Steve -------------------------------------------------------------------------- Later vehicles made in the last decade or so mostly have a stupidly complicated system which is all to do with "evaporative loss control" i.e. removing hydrocarbon emissions into the atmosphere. My 90 has a slight negative pressure in there, so does the Disco, but I think they must keep it to a small pressure differential to remove chances of tank damage, while not letting any nasty things out to damage all the little ozones In the good old days of course nobody worried about such rubbish like how much fuel vapour escapes from your tank into the atmosphere, and a good old fashioned vent was plenty good enough ------------------------------------------------------------------------------ Orange, You are correct, however I have found they need setting, there is a 10mm nut on the bottom of the cap, tighten until on fitting to the base part its as tight as practical, then grease up the O ring and all is ok I basically needed to test my Tig Weldied funnel..... so I fitted cap to funnel, turned upside down and filled with petrol, left overnight...it was all still there this morning ! Nige Link to comment Share on other sites More sharing options...
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