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Old 06-09-2016, 03:47   #1
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Do I need an electric pump when fitting extra fuel filters?

Dear Experts;
I have an old motorsailer (1976) with twin Perkins 236s (with two tanks which feed a single transfer/engine feed pipe).
The only fuel filtration is a single separator/filter just before the lift pump on eacb engine.
I am planning to fit another separator/filter to each tank (and maybe to keep each tank independent of the other except for a possible emergency transfer system).
I like the idea of fitting two units in parallel for each tank to allow a switch-over when one filter needs to be replaced. Also nice to have would be a vacuum guage (with mechanical max vacuum indicator).
QUESTION: should I fit a pump to pull fuel through the new filter(s) and if so a) how powerful should it be and b) would such a pump be really useful for bleeding the engine? (I would need one each side, of course).
I am also planning a separate slow steady filtration system each side: a separator/filter and pump sucking from a pickup low down and returning quite low in the tank to reduce foaming.
All this to be done after draining the tanks and manually cleaning them. The tanks were cleaned at some point before my ownership but not in the three years since, so it could easily be six or eight years ago (when engines were rebuilt).
If I need four pumps for this set up, can I buy four the same or should the tank filtering pumps be different from the engine filter/feed pumps (if they are needed)?
Thanks for any comments!

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Old 06-09-2016, 06:18   #2
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Re: Do I need an electric pump when fitting extra fuel filters?

Technically no... Practical application yes... How's that for avoiding a straight answer?

I am sure you will get a number of conflicting answers, but here is my $0.02 (and worth every bit of it) Back before I downsized, I always ran an electric "lift pump" on the Perkins filter system. Logic and system details as follows.

Vacuum levels generated by engine mount mechanical pump are well below the 12-15 psi generated by an electric pump. Helpful with a partially restricted filter system (always at a critical time).

Running the lift pump while bleeding the injector pump/injectors saved my thumb from falling off while trying to keep the system full with the mechanical pump lever. Also easier as mehanical pump is on other side of engine from injector pump .

Because system is running under pressure rather than vacuum, possible hard to find air leaks show up as easy to find fuel leaks. (It happens)

When swapping out filters, lift pump will fill bowls from tank rather than trying to fill in place. Leave bowl loose till it weeps, tighten down and ur done.

If she were mine, this is what I would do... (Your mileage may vary)

I would leave the tanks manifolded together via a 3 way valve. Tank 1, Tank 2 or Both (Think battery switch) Prevents using a single tank all the time (Old fuel/water in non used tank) while still allowing isolation if known problem. In unknown areas you may wish to fill single tank with suspect fuel to avoid cross contamination if you get a bad batch... Either or.

Both tanks should be fit with a visible fuel/water separator before the 3 way valve (No Filter) Biggest contamination suspect always.

After 3 way valve fit 12psi electric lift pump. (Good quality automotive is way cheaper than "marine" and adequate) Between pump and filter assembly install a 4psi pressure regulator to knock pressure down to Racor rated pressure of 4psi.

Next come filters... You can install one pair for both engines or a pair for each. Depends on your space and budget. Racor 500 filters are rated at 60 gal per hour so no problem with capacity. 4 filter set up is just belt and suspenders

Each filter setup consists of 2 Racor 500 filter/water separators. Filter elements are cheap and compact. much more so than "spin on" types.
Filters are ganged together with a "stack valve" which changes the inlet and outlet at the same time from Filter A to Filter B with one 90 twist. Also has ports for a pressure guage (remember were blowing now not sucking ) to show pressure drop across the filter element. This setup lets you 10 micron filters will grab 99.9% of the garbage and a 5 in the engine mounts will catch anything else significant.

More info than you really wanted huh? Well it worked for me for a lot of years... Nice to be able to switch over filters with a quick twist and change elements at your convenience

"It seemed like a good idea at the time"
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Old 06-09-2016, 08:30   #3
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Re: Do I need an electric pump when fitting extra fuel filters?

Well Capt-C, that's the kind if good stuff I wanted to get; thank you!

Not sure if I will go the exact route you suggest, retaining the transfer pipe (bcs I do expect to take on poor fuel in the Pacific, and expect muck to suddenly bloom in a tank every now and then). But your advice on the pump and especially the pressure regulator is close to priceless. (And also I am glad I am not the only one who resents all that thumb work when bleeding the filters!).

Thanks again!
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Old 06-09-2016, 16:45   #4
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Re: Do I need an electric pump when fitting extra fuel filters?

I have pumps like the pic inline. About $16 on ebay. I only use them when changing secondary filters or when an engine has sat for a long period. I have Detroit mains, so bleeding isn't a problem, but the pump circulates the fuel for an easy start.
The engine mounted pump pulls thru the electric pump without problem.
A vacuum gauge goes anywhere between the primary and your lift/electric pump. On my Racor housings, a new filter reads 0. I change when it reads about 7. I run 2 micron filters in my primaries. I get about 500 hours out of them. My secondary filters never get dirty, but I change them once a year because they catch some water.
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Old 06-09-2016, 23:28   #5
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Re: Do I need an electric pump when fitting extra fuel filters?

Have you installed the electric pump(s) to suck through all the filters or to push through them, or in between primary and final? Good info that you can run the engines with the electric pump not switched on; is that true of all in-line pumps?
Could you explain why Detroit diesels are easy to bleed?
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Old 07-09-2016, 07:41   #6
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Re: Do I need an electric pump when fitting extra fuel filters?

We have used a small pump for years. It installs just before the first racor filter so when changing out filters you don't have to slosh fuel around. Just fill the housing from the little pump. It's probably the best cheap upgrade you can add. In a pinch even those fuel bulbs will work, but if you have a long fuel line they can take forever.

- If animals weren't meant to be eaten then they wouldn't be made of food.
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Old 07-09-2016, 21:28   #7
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Re: Do I need an electric pump when fitting extra fuel filters?

Thanks again: I am now starting a new thread about how low down in the tank should be the pick-up point. Why not have one pick-up point at the absolute bottom of the tank, with fuel being circulated through an initial water separator/filter and electric pump daily, weekly, or whatever when the engine isn't being used; so all the water, crud etc does not build up? It just seems crazy that the standard yacht approach means we cannot stop the mucky stuff building up and we are guaranteeing that as soon as we use engines in rough conditions we are going to get that stuff into the engine intake filters - which may or may not cope.
What is best commercial practice?
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Old 08-09-2016, 00:40   #8
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Re: Do I need an electric pump when fitting extra fuel filters?

Further to my last post saying I would start a new thread, asking why not use one pick-up point for both fuel "polishing" and feed for the engine:

Well, I have decided not to open that discussion, as I guess there is one good answer: if a big piece of something (a metal flake, a bit of plastic or whatever, some ball of sludge, whatever...) were to block the one pick-up point, there would be no way to use that tank until the blockage is removed.

Best commercial/fishing practice seems to be filter, filter, filter and burn it as fast as possible - maybe with keeping a day tank for cleaned fuel separate from the main storage tanks. (Though ships using dirtier fuels than diesel do have sophisticated fuel cleaning/re-cycling systems.) "Polishing" might be a need for pleasure vessels and for onshore storage facilities such as for hospital generators (because the fuel sits for so long), but maybe we should just use our vessels more or at least cycle the fuel faster!

Anyway, I will following the guidance above as far as feasible (taking full responsibility if I do not do as recommended in any respect!). I will set up a "polishing" loop for each tank and install multi-stage filtration with pump(s), gauges and (if space allows) parallel-isation.

But, most of all, I will clean the tanks and make sure I can inspect them easily and do so annually.

I will report back next year when the works are completed. Thanks to all!

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