Subject: RE: XJ6's next trick, was Jaguar on Holiday.
Well the mail to OZ is a little slow at the moment and I have solved the
problem before anyone managed to reach me...here's what I said...
>And for my next trick the Jaguar XJ6 will now make hard-to-locate petrol
>smells :-)
>
>I can smell petrol in the cabin (after the car has been sitting for some time
>in the sun or on hot days or after a warm drive). The smell is comming from
>somewhere around the boot and more specifically the right hand tank. I have
>ruled out the possibility of the fuel - filter, pump, return-valves, change
>over valve or associated (in boot) connections and can't find any liquid
>petrol anywhere it's not supposed to be :-)
>
>I suspect something has come off or gone wrong with the vapour collection
>/separation (pollution control) apparatus that lives in the rear pillar and
>top inside boot. When I open the RH tank after a run there is considerable
>pressure build-up and a "whoosh" of petrol fumes and you can hear the tank
>poping back into shape as I open the cap. Is this normal? I thought the
>pressure should be bled off and the fumes sent to the canister under the RH
>(front) wheel arch. So what would you look at first in such a situation?
Well it turned out to be the in-line "pressure relief valve" between the
carbon canister (located in the front RH wheel well) and the tanks.
Phoning around all the Jag mechanics I knew everyone told me to replace
the charcoal canister ($200 US), vapour separators (2 X $90 US) or both.
When I was sitting down staring at the "emission control" section in the
workshop manual I noticed "part 5 = Pressure release valve". Tracing the
vapour line from the rear tanks to the canister at the front I managed to
locate a small inline plastic cylinder/cone thingy that looked suspiciously
like a valve. I pulled it out of the line and ... Whoooooshhhhhhh! fuel
fumes a-plenty. Once I cleaned it up with metho I sucked and blew on it
and could not get any gas through it...after repeated washing in meths
and bashing I finaly got it to go "pop" when I blew through it and let
gas through. All the manual said about the said device was that it
"allows a certain amount of pressure to build up before releasing fuel
vapour to the canister. It has a vacuum releif also".
Real helpful...why was it there? what was the functional significance to my
beloved Jag.
To test it was the culprit I went for a drive with the valve off and the
vapour line flapping free under the front wheel arch...no fuel smells and
the tanks did not pressurise. So next to see if the carbon canister was
restricting the flow I put the valve back on the tank side of the vapour line
but left the canister unconnected to the other side and went for a test drive..
the tanks pressurised and the fuel smell was back this convinced me it was not
the canisters fault as the valve was the only thing between the tank and
the atmosphere. After frobbing and tweaking the valve to get it working
reliably for well over an hour it was still a little sticky (at this point
I had no idea what a "good" valve should behave like but I guessed that
if I was having difficulty blowing/sucking through it and given that it
seemed to release at varying pressures that it must be faulty, sticking.
The vacuum releif operated easily but getting gas to flow in the opposite
direction was difficult).
Solution: Upon finding out that this device was going to cost me $45 US
to replace (remember this is the simplest of small plastic valves) and
the part would take 1 week to arrive I decided on a temporary fix that
is likely to become permanant I ran my drill through it making a neat
hole in the valve diaphragm. Now I am not one who usually likes to
"hack" cars, preffering to replace broken parts with the correct type
and in the correct way...but in this case I could not help myself :-)
the thing is designed to let vapour flow both ways and the hole I just
made allows it to do that more easily ;-) Now it was easy to blow through.
After installing it I went for a test drive and all appears to be well again
, no fuel smells and no pressurised tanks :-)
This is the second time I have "modified" my Jag, the first time
I placed a inline filter before the electric fuel pump, this time
I effectively removed an inline pressure vlavle from the fuel vapour line
...thus nature is ballanced? :-)
Regards Scott
_______________________________________________________________________________
Scott Fisher [scott@psy.uwa.oz.au] PH: Aus [61] Perth (09) Local (380 3272).
_--_|\ N
Department of Psychology / \ W + E
University of Western Australia. Perth [32S, 116E]--> *_.--._/ S
Nedlands, 6009. PERTH, W.A. v
Joy is a Jaguar XJ6 with a flat battery, a blown oil seal and an unsympathetic
wife, 9km outside of a small remote town, 3:15am on a cold wet winters morning.
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