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Old 21 January 2009, 19:46   #1
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Priming bulb before or after filter?

I am refurbishing a rib that has fuel lines which are all over the place. It has an internal fuel tank with twin fuel lines (disconnected) as well as two fuel cells (connected) and two seemingly redundant lines that have engine fuel line fittings. The previous owner reported the fuel lines from internal tank fed insufficient supply to two 75hp motors. (This may have been because they were very narrow bore and were teed off a single feed off main tank) I have cleaned the tank, added a wider bore outlet (2 x 10mm spigots) and I am ready to re-run fuel lines.

I shall strip out all existing lines but seek advice on the bore of the fuel lines that I should run from tank to filter inlets, is 10mm okay? Also where to put priming bulbs in-line. Should they be before the filter or between the filter and the engines?

Finally, I live in the Middle East and will be running the engines regularly however bearing in mind high ambient temps should I run the engines after use (and flushing etc) to drain fuel system or is it okay to leave fuel lines connected and system full

Many thanks for any advice.
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Old 21 January 2009, 20:02   #2
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I've always used: tank>bulb>filter but I don't imagine it is critical. I guess the filter has some resistance to fuel flow and fuel is drawn into the bulb only by its own expansion after it has been squeezed, so putting the filter before it will slightly restrict the flow to the bulb.
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Old 21 January 2009, 20:45   #3
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Thanks JW
I even wondered about 2 priming bulbs one either side of the filter however I am always wary of using too much pressure to push fuel into engine fuel system.
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Old 21 January 2009, 21:01   #4
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Quote:
Originally Posted by Andy Young2 View Post
...I even wondered about 2 priming bulbs one either side of the filter...
Nah, more to go wrong.
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Old 22 January 2009, 03:43   #5
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dont really think there's wrong or a right way, but just think, bulb pulling fuel from tank also pulling any particials thats in the fuel, i'd rather the filter have them first than my primer bulb, does that make sense?
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Old 22 January 2009, 03:59   #6
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I rigged a rib with twins on it last year and I cocked up cutting the fuel lines, I think I may have been thinking more about getting out and playing sorry "running them in" than the job in hand. I ended up with the bulbs after the filter and... it did not work. It was with empty brand new filters etc but the bulbs seams to have more push than suck and could not suck fuel into the filter.



Tank - Bulb - Filter - Engine
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Old 22 January 2009, 04:11   #7
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Tank-filter-bulb-engine is how I was taught!
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Old 22 January 2009, 04:18   #8
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i was probaly taught that to, but i put it in the logical part of my brain and forgot someone actually told me
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Old 22 January 2009, 04:28   #9
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I agree with j walker and MDT
I would definetley put the primer bulb BEFORE the filter, ie Tank/bulb/filter/and this is my logic behind it.



The primer can only lift fuel a small amount so it should be as close to the tank as possible there will be a strainer in the tank which will filter out any crap that could block the bulb.(and if theres that much crap in the fuel tank then its going to cause problems anyway)
If you end up in the situation where the filter partially blocks with the bulb after the filter, the fuel pump in the engine will suck and collapse the primer bulb and the engine will stop. there is nothing you can do other than change the filter at sea.
with the filter after the bulb, if you get a partial blockage in the filter you still have a primer bulb that can suck fuel up from the tank, and you stand a chance of getting to safety by getting someone to continuously squeeze the bulb to pump the fuel through the filter so you can get to safety,

as someone pointed out, bugger all suck but a fair blow
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Old 22 January 2009, 04:28   #10
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Common sense really, under normal use, the primer bulb is the only thing you'd need to access, hence the reason for these!
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