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Old 28-01-2015, 19:03   #16
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High diesel filter location or header tank

Snowpetrel, I can't see how you could hydro lock a Diesel engine doing what you suggest. Maybe I am missing something from your original question but the pressure required to "crack open" the injector nozzles on my engine is in the order of 1800 psi. My tank sits above the engine with a small drop to the filter and down from there to the engine. Total drop around 2 feet, so around 1 psi. No problems after 30 years.

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Old 28-01-2015, 19:55   #17
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Re: High diesel filter location or header tank

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Originally Posted by GILow View Post
... the pressure required to "crack open" the injector nozzles on my engine is in the order of 1800 psi. My tank sits above the engine with a small drop to the filter and down from there to the engine. Total drop around 2 feet, so around 1 psi.
Thanks matt. That's the kind of reassurance I was after. I guess I was thinking with a worn punk and old injectors it night be possible to get a slight keakraban. But by that time the engine is probably not going to run anyway. Do you always close your fuel valve when you leave the boat ?


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Originally Posted by Mr Filter View Post
You don't want to place the filter that high. If you have any type of air leak the air will be trapped at the highest point. This will cause and air lock.
Just occurred to me that the engines secondary is curently the highest point with no bleed off. So any airs going to get trapped there anyway?

I really appreciate all the input. It helps when thinking through these things to bounce ideas of you guys. Cheers



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Old 28-01-2015, 20:07   #18
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Re: High diesel filter location or header tank

G'Day Ben,

I have no particular expertise, but in Insatiable II the primary filter pair are ~300 mm above the lift pump, and the fuel in our keel tank, when near MT is down about 1.8 m from the lift pump. Runs ok, no air issues. Only problem ever is when drawing from the keel tank, if it is left sitting for a few days apparently some fuel runs back down the line and it may stumble a bit when first started up. So mostly we transfer fuel from the keel to the saddle tanks as required...

Oh, we never shut off fuel valves, FWIW.

I don't think your proposed setup will be any problem at all.

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Old 28-01-2015, 20:12   #19
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Re: High diesel filter location or header tank

Quote:
Originally Posted by Snowpetrel View Post
Do you always close your fuel valve when you leave the boat ?
Geez mate... not in public please! I mean, what am I going to do... admit that I don't on THIS forum? If I was silly enough to admit that I'd get roasted.

Oh, I did just admit it... oops.

Seriously, I should, but I don't always remember. And I know the previous owner didn't because the shutoff cock was siezed when I bought the boat.

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Old 28-01-2015, 20:13   #20
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Re: High diesel filter location or header tank

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Oh, we never shut off fuel valves, FWIW.
Stand by for the roasting....

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Old 28-01-2015, 20:19   #21
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Re: High diesel filter location or header tank

Fuel filter can be mounted at any height above engine/fuel tank.
You know how a syphon works ?
Once all the air is out of the filters/lines an height difference
Will have no effect.
The only issue will be bleeding the system.
for this you will need some sort of pump in order to supply
positive pressure to enable bleeding.
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Old 28-01-2015, 20:33   #22
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Re: High diesel filter location or header tank

One of the best fuel systems I've seen on a cruising sailboat utilized a large day tank, the bottom of which was slightly higher than the engine's fuel lift pump. Fuel was supplied and returned only to/from the day tank. A sight gauge read fuel level, directly. A manual, high capacity, transfer pump drew fuel from each tank through a valve manifold. Filters were gravity fed from the day tank.

This provided very precise fuel management. And virtually eliminated the chance of engine failure due to an air leak (otherwise a common failure mode), as the engine's fuel system was gravity fed.
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Old 28-01-2015, 21:03   #23
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Re: High diesel filter location or header tank

Quote:
Originally Posted by John Boor View Post
My filter is above the lift pump by actually 12 ins. When I replace my filter I open the drain cock at the bottom of the bowl then crack the top of the filter housing allowing a small amount of fuel to drain (about 2oz) close the drain cock , removeing the old filter slowly and replace with new one slowly then turn on the ignition (I have an electric fuel pump) allowing the fuel to flow through the system and purging the small amount of air in the top of the filter. My Westerbeke 4-107 came with a mechanical lift pump and I would purge the line with the lever on the pump after opening the bolt on the engine filer housing until no bubbles can be seen. I believe that once the lines have been purged of air the lift pump does not work any harder at above, level, or below the pump.
You are correct. The suction required to lift the fuel to the high point is returned as the fuel falls to the lift pump. 6-cyl Westerbeke The Racor filters are about 3 feet above the lift pump and 5-6 feet above the day tank. I have an electric precharge pump for pressurizing while filling & purging. Open any downstream vent & hit the button. Racors fill & air is purged.

Having the filter high also prevents accidental siphoning & leaking since its always at a slight vacuum.
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Old 29-01-2015, 04:14   #24
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Re: High diesel filter location or header tank

Thanks for that pic Nicholson58. It's nice to see another boat with filters mounted above the engine. And to the other posters, yes as long as the syphon holds it should be the same as having filters down low. But if any air gets into the system (and its more likely to being under negative pressure) then the engine side could become presurised. I guess the solution is to make sure air is not able to get in...

I think I'll put it there and try it for a while. It's already basically plumbed in. And will be easy enough to shift in the future if I decide I don't like it there. Cheers

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Old 29-01-2015, 06:56   #25
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Re: High diesel filter location or header tank

No, we do not shut off the fuel unless I am working on something that requires it. Never a problem, and I don't understand how one even could hydrolock an engine with fuel.

I would venture the vast majority of boats I have been on have the primary fuel filter mounted higher than the engine and tank. Pretty much all power boats I have been on have the filters and other maintenance items mounted conveniently at chest height, while the engines are lower.

I simply don't understand the "expertise" here issuing warnings about this. It is a complete non-issue.

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Old 01-02-2015, 05:04   #26
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Re: High diesel filter location or header tank

I got the system completed friday, and left it full of diesel for two days to check for any leaks. It seemed OK, and the engine started and ran fine today for half an hour, so at this stage no problems with the high setup, it seems to bleed the air out fine, and it is nice not to have to fumble around in the bilges to change the filter, or inspect the water trap, with everything being in clear view.

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Yes the plumbing is all a mess! I've still got to make a board that it will all be neatly clipped onto. The water hose is for the vented loop, with a small filter to catch any bits of impeller before they stick in the heat exchanger, and takeoffs for the stern tube cooling and tell tale/syphon break.
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Old 01-02-2015, 05:38   #27
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Re: High diesel filter location or header tank

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Originally Posted by Snowpetrel View Post
I got the system completed friday, and left it full of diesel for two days to check for any leaks. It seemed OK, and the engine started and ran fine today for half an hour, so at this stage no problems with the high setup, it seems to bleed the air out fine, and it is nice not to have to fumble around in the bilges to change the filter, or inspect the water trap, with everything being in clear view.



That's great.

I'd bet most of us took your original "above the engine" location too literally.

It appears what you meant was: "I have lots of room. Would a location of the filter at a level above the top of the engine, but not immediately above it, be acceptable?"

Or something like that.

You've proven that the siphon concept works as suggested, since once the pump fills up the filter and lines, they will stay filled. Happpens all the time, unless you spring a leak.
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Old 01-02-2015, 09:55   #28
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Re: High diesel filter location or header tank

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That's great.

I'd bet most of us took your original "above the engine" location too literally.

It appears what you meant was: "I have lots of room. Would a location of the filter at a level above the top of the engine, but not immediately above it, be acceptable?"

Or something like that.

You've proven that the siphon concept works as suggested, since once the pump fills up the filter and lines, they will stay filled. Happpens all the time, unless you spring a leak.
[/LEFT]
Yep, I thought it was going to be right over the valve cover!
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