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Old 12-01-2016, 08:51 PM   #21
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Common problem with clogged lines. Have them "blown" out and back flushed. Also, recommend youchave the tanks cleaned.
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Old 12-01-2016, 08:57 PM   #22
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Not my intend to hijack the thread (sorry PO) but all these posts raised a question in my mind (or what is left of my mind).
My diesel return line is returning not to one of my fuel tank but to the fuel line just before the primary filter. Is this something common, normal or not desirable?

l.T.
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Old 12-01-2016, 09:15 PM   #23
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Crazy. It must run to a manifold someplace
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Old 12-01-2016, 09:31 PM   #24
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Originally Posted by Lou_tribal View Post
Not my intend to hijack the thread (sorry PO) but all these posts raised a question in my mind (or what is left of my mind).
My diesel return line is returning not to one of my fuel tank but to the fuel line just before the primary filter. Is this something common, normal or not desirable?

l.T.

Some engines do that. Some engines pump only a bit more than they actually use thus return only a small portion of the fuel back to the tank. Sometimes those engines plumb the return line directly to the fuel filter.

Some engines pump a lot of fuel and use only a smaller portion of the fuel pumped. These engines almost always return to the tank[s]. On these engines the return fuel will be very , very warm and use the tanks as a heat sink.

There is a catch to the first group and that can be from any air picked up from a leaky injector or from a leaky fuel pickup line. That air will accumulate at the filter and shutdown the engine by air binding the injection pump.. It will become impossible or very difficult to purge the air. The return to filter or injection pump type engine will not run untill the source of the leak is repaired.

The return to tank engines will purge the air to the tank where it can escape. Some engines, many are not, are capable of purging small amounts of air from the injection system so if the leakage is then dumped back to the tank the engine can run, maybe roughly , but it will run.
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Old 12-01-2016, 09:56 PM   #25
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Some engines do that. Some engines pump only a bit more than they actually use thus return only a small portion of the fuel back to the tank. Sometimes those engines plumb the return line directly to the fuel filter.

Some engines pump a lot of fuel and use only a smaller portion of the fuel pumped. These engines almost always return to the tank[s]. On these engines the return fuel will be very , very warm and use the tanks as a heat sink.

There is a catch to the first group and that can be from any air picked up from a leaky injector or from a leaky fuel pickup line. That air will accumulate at the filter and shutdown the engine by air binding the injection pump.. It will become impossible or very difficult to purge the air. The return to filter or injection pump type engine will not run untill the source of the leak is repaired.

The return to tank engines will purge the air to the tank where it can escape. Some engines, many are not, are capable of purging small amounts of air from the injection system so if the leakage is then dumped back to the tank the engine can run, maybe roughly , but it will run.
Thank you verynmuch for this information!
For what I know, my engine is consuming very small diesel and is very rudimentary and as it is running like this for quite some time I would tend to think it is fine but if anybody think it is not I am open to comments. On the temperature side it is fine, I checked the return line with a heat gun and the temp is on the normal side.

One other thing that will make other people jump 2 feet above their chair is that I have a single fuel filter! While this makes me a bit nervous and I tend to want to add more, my engine can run on anything can could be ran or almost. I found people thatbwere ablenmto run it using old engine oil, cooking oil, or even more exotic hydraulic oil or transmission oil! So as it is running with one filterbfor 20 years (ormore) and as boat diesel is the same as car diesel up here, I guess that is fine.

L.T.
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Old 12-01-2016, 10:09 PM   #26
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You should have secondary fuel filters on the engines.
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Old 12-01-2016, 10:21 PM   #27
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And I have I have none this what makes me a bit nervous
Is it possible to add one? What kind? Any impact on the fuel pump? I really do not know!
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Old 12-01-2016, 10:29 PM   #28
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Easy add in line. Can't believe there is not a pair of canister filters on engine. Add another Racor with bypass valve in case 1st one gets clogged. Also allows filter replacement and sump drain while underway. You can stagger fuel micron filter size. Maybe 20 on the 1st 20 on second..
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Old 12-01-2016, 10:30 PM   #29
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Correction 10 on the second
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Old 12-01-2016, 11:06 PM   #30
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Mr MV, my engine is kindof very rough one and old one that came from military trucks to fishing boat to my boat from the hands of a pretty good diesel mechanic (by pretty good I mean a guy who was a mechanic, who bought a hull, built a boat on top of it, rebuilt an engine before put it in this boat, so better than I will ever be).
From what I know from old papy diesel for cars and other things filtering was not very high tech .
This said I fully agree I should add a secondary filter and more a last chance filter before the pump. The only reason it is not done yet is because I do not know if there is any impact on the fuel pump. I do not want to **** up a working system.
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Old 12-01-2016, 11:07 PM   #31
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Peter B (ie Moi), said...
if that's the case, leaving both taps there before the filter open might allow them to equalise at that point as long as that filter is below the fuel levels, saving rigging up yet another connection. Have you tried that? After all, it might be why the PO didn't have a problem..? Then the return fuel line going to just one tank would not matter either, as they would just equalise as you go along.

Don't think this will work either as the fuel lines exit the top of the tanks - at least I've never seen it do it on mine...
That is irrelevant, as the fuel pick-ups should go down to near the bottom of the tank, and siphon effect should take care of the rest, just as long as the primary filter, where the two shut off valves are situated, is well below the usable fuel level, I would think.
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Old 12-01-2016, 11:10 PM   #32
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PO on my 34 installed a valve which I can direct the return line to either tank. Generator always goes to starboard tank but engine can be directed either way. I normally direct the return to the tank with less fuel in it which helps keep the listing of the boat to a minimum. If the boat is listing to port, I direct the return flow to starboard.
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Old 12-02-2016, 09:24 AM   #33
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Did not read every post so excuse if repeating.
You do have a balance line of sorts when both valves are open. With your return line going only to one tank, they should both be open. At least for the time being until you set up your fuel system with two returns.
If your vessel has a "built-in" list, due to generator or battery placement for instance, then a crossover line will make it worse by allowing fuel to flow from the higher to the lower tank.
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Old 12-02-2016, 09:53 AM   #34
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That is irrelevant, as the fuel pick-ups should go down to near the bottom of the tank, and siphon effect should take care of the rest, just as long as the primary filter, where the two shut off valves are situated, is well below the usable fuel level, I would think.

and therein lies the rub, Mainship installed the primary filter level with the top of the tanks.
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Old 12-02-2016, 01:47 PM   #35
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ABYC H33 Diesel fuel systems ... (paraphrased) All fuel must return to the tank from which it is drawn.
My boat has a single engine but two fuel tanks. It draws fuel from both unless I manually close one off. Excess fuel is returned to both tanks unless I manually close one off.

How would the system know which tank the fuel originally came from?
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Old 12-02-2016, 01:51 PM   #36
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Recently bought a 1982 Mainship 34 after years of sailing. Confronted with a distinct list to port and assuming it is caused by an unequal fuel load. Lines from both tanks are open. Starboard tank reads half full, port tank reads empty but suspect sender is inoperative as that is the low side of the boat. Bilge is empty and water tank amidships. Any suggestions will be greatly appreciated. Bill
I'm going to suggest something that will help you decide if the list is caused by an unequal fuel load as well as determine if your fuel sender is working:

Fill both tanks completely.

Now you know that there is an equal amount of fuel in each tank and you know that both gauges should read "full".

Take it from there.
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Old 12-02-2016, 04:14 PM   #37
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Excellent suggestion.

I have an 82 MK1 as well, my boat when I purchased it had quite a load of lead bars in a port locker in main cabin. After filling tanks and moving some batteries around removed the lead to balance the boat. My fuel return lines go to both tanks, but no valves to choose which side.
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