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#41 Update

Posted: Tue Jan 08, 2019 4:13 pm
by Vonkie
Well, 681 miles since the fuel starvation scare and not the tiniest sign of a recurrence. Driving beautifully, and, on open roads, at over 20 miles per gallon. The intervention was minor, merely replacing the extra filter on the fuel line at the back near the pump.

Hold thumbs.

Meanwhile, the love affair continues.

#42 Re: Sudden complete loss of fuel delivery

Posted: Thu Jan 10, 2019 9:46 am
by PeterCrespin
Just be aware that you may be on borrowed time in two important respects:

1) Silicone (not silicon) is not to be used on fuel joints. It is neither foolproof nor fuel proof and will expand, go soggy and break off to cause trouble, as you have found. Any reputable silicone brand will have a written warning to this effect on the tube or packaging. Your ‘mechanic’ owes you for the flatbed expense IMO.

2) Dave Rose, for whom I have the highest regard, and the sellers of your bowl filter (who I probably can guess and hold in equal esteem) are both wrong on how the filter SHOULD work. The reason for including a glass bowl or sight glass in a fuel supply is to permit visual inspection. Most of us probably looked at the spinning wotsit in the glass bowl on old pumps when we were kids, up near the hose attachment at the top of the pump. Nowadays it’s probably still there but inside the pump casing.

As designed by AC and supplied/plumbed by Jaguar, the fuel first enters the glass bowl from the inboard connection and via the centre of the alloy casting through a hole in the middle of a flat gauze on the earliest cars, or a later toroidal (doughnut-shaped) element. This dirty unfiltered fuel emerges from the fast flow in the narrow fuel pipe and slows down in the comparatively large calm space of the bowl. This encourages the water and sediment or paint flakes to separate out and fall to the bottom (most appropriately checked by popping the bonnet first thing before starting the engine). The bowl is large and will collect a lot of water or junk before the lumpy bits impede flow.

When running, the fuel is pumped through the element and leaves the filter bowl via hole(s) from the periphery of the casting that exits via the outboard fitting to the carb feed. Correct original filter elements therefore have a hole in the middle, filter from the outside-in, leaving dirt in the glass bowl, and are held in place by the rim at the top.

What Dave described is what happens when you use the wrong element, closed at the bottom, filtering from the inside out and held in position by a spring. They work OK most of the time on clean systems but can and do hide problems like debris in fuel by hiding it inside the element. They can cause fuel starvation that fools people because the glass bowl appears clean.

#43 Re: Sudden complete loss of fuel delivery

Posted: Thu Jan 10, 2019 11:41 am
by mgcjag
This link could be of help....showing the type of filter that works from outside to inside, with the hole in the bottom and not useing a spring to hold it in place....Steve ... ter#p57843

#44 fuel filter

Posted: Thu Jan 10, 2019 4:52 pm
by Vonkie
Thanks guys, also for the interesting (if somewhat bewildering) link to the thread on filters.

When I first had a blockage issue, I noticed the different filters. The Service Manual at C.14 has the gauze filter assembly (first image below), which seems identical to the current set-up but for a frisbee-disk gauze filter (item no. 41) instead of the concertina filter supplied by SNGB. The SNGB catalogue, for its part, has for the Series 1 only the concertina filter (hole on top, spring bottom) as part number C28080 (second image below). Mine is the SNGB filter (photo below).

I was advised, and seem to recall amateur searches corroborating, that the concertina was thought superior to the gauze disk and became the only unit supplied as after-market by the likes of SNGB.

Don't we now have Julian Barratt agreeing to weigh in where appropriate on things like this? I would appreciate advice as to whether I should try to move to the gauze disk and if so, what part number this is supplied by whom.

Also, please advise whether the particle residue shown on my pictures posted on 23 November above (in the filter bowl and on the paper towel after wiping) is of a normal or disconcerting quantity.





#45 Re: Sudden complete loss of fuel delivery

Posted: Fri Jan 11, 2019 9:56 am
by mgcjag
Hi Frank.....I will start a new thread in the Technical section on filters and see what comes up....will contact Julian SNG and ask him to look at your dirt in the filter bowl and is it acceptabel.......thats awkward to you know you want clean fuel into the carbs.....each carb also has its own filter..ideally the filter in the glass bowl should clean the fuel....but depends how bad tbe fuel is and how good the paper element is....I gave the link to show the options...Steve.....