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Nanni Diesel problems - Fuel Filters


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27 minutes ago, marinheiro said:

something looks a bit strange with the engine mounted filter.

Where does the braided line on the inlet side originate? Should be from the lift pump.

The outlet side appears to be connected to the injector fuel return?

The filter outlet should be feeding the injector pump, the fuel return line should be going back to the fuel tank.

Where is the injector pump getting its fuel from? 

Look again - its not obvious.  Refer Kevin's last photo

The fuel lift pump is located on the engine block under the pressure pump/governor.  The supply and pressure lines are on the left of the pump as we view it (bottom middle of the image).

The lift pressure line loops and comes over the top of the pressure pump inlet banjo (more on this later) before attaching to the secondary filter inlet.

The sec filter outlet drops vertically out of sight behind the filter and comes to the pressure pump inlet banjo.  This is a double banjo (horrors - duelling banjos!) and a second line on it can be seen running toward the back of the engine.  This is the fuel return/airbleed line.  It will likely have a restrictor in it.  The lift pump supplies excess fuel - some of it bleeds back to the tank via this line, and any air can also bleed via this line.

The pressure pump and governor do their business and send pressurised fuel to the injectors.  A small low pressure return line is fitted to the injector rail returning to the low pressure side of the pressure pump - this is the line we see terminating at the outlet of the secondary filter.  Again, this allows for air bleed.

 

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16 minutes ago, aardvarkash10 said:

Look again - its not obvious.  Refer Kevin's last photo

The fuel lift pump is located on the engine block under the pressure pump/governor.  The supply and pressure lines are on the left of the pump as we view it (bottom middle of the image).

The lift pressure line loops and comes over the top of the pressure pump inlet banjo (more on this later) before attaching to the secondary filter inlet.

The sec filter outlet drops vertically out of sight behind the filter and comes to the pressure pump inlet banjo.  This is a double banjo (horrors - duelling banjos!) and a second line on it can be seen running toward the back of the engine.  This is the fuel return/airbleed line.  It will likely have a restrictor in it.  The lift pump supplies excess fuel - some of it bleeds back to the tank via this line, and any air can also bleed via this line.

The pressure pump and governor do their business and send pressurised fuel to the injectors.  A small low pressure return line is fitted to the injector rail returning to the low pressure side of the pressure pump - this is the line we see terminating at the outlet of the secondary filter.  Again, this allows for air bleed.

 

OK, did not pick up the double banjo connection.

Still not good practice to have the fuel return looping back into the injector pump feed, the fuel will be hot and will amplify any entrained air issues. 

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Just now, marinheiro said:

OK, did not pick up the double banjo connection.

Still not good practice to have the fuel return looping back into the injector pump feed, the fuel will be hot and will amplify any entrained air issues. 

and yet its been like that for 30 years or more...

The amount of fuel returning on that line from the injector should be tiny.  If its enough to cause a heated fuel problem, there are bigger issues elsewhere.

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I've been down a rabbit hole for a while learning about banjo bolts and double banjo bolts which I'd never heard of. But I can't figure out which fuel line or lines we're talking about.

For posterity on this thread I thought I'd cut and post the

Nanni 15, 2 cylinder 2-60he Technical data and maintenance items in case someone needs them (did they mispell diaphragm as diagram (I have no idea what these are anyway)?

ENGINE SPECIFICATION
Number of cylinders : 2
Displacement : 570 cc
Bore - Stroke : 72 X 70 mm
Compression ratio : 22/1
Max. pressure difference between cyl. : mini 28b
Compression pressure : 30kg/sq.cm
Maximum speed without load : 3300
Maximum RPM in load : 3000
Idle RPM in forward gear : 850
Max. torque :
Firing order : 1 - 2
Rotation : Anti clockwise

INJECTION
Type of injector : DN 12 SD 12
Fuel injection pressure : BOSCH PFR 2KD50
Injection pump manufacturer : 140 b
Injection timing : 25° before top dead
center

TIGHTENING TORQUE
Arm head cover cap nuts :
Cylinder head bolts : 6 to 6.5 MK - engine hot
Flywheel bolts : 5.5 to 6 kg
Connecting rod bolts : 2.7 to 3.5 kg
Rocker arm bracket nuts :
Main bearing caps bolts : 3 to 3.5
Main bearing caps bolts : 2 to 2.4
Nozzle holder assembly :
Glow plugs :

LUBRIFICATION
Oil pressure at idle RPM : 1 bar
Oil pressure at maximum load : 3b to 4.5b
Recommended oil : API CD 15W40
Oil pan capacity
- mini :
- maxi : 2.2 l
Gearbox model : HBW
Oil capacity : 0.3 l
Recommended oil : ATF

DIAGRAMS
Valve clearance (cold)
Inlet : 0.15 to 0.20 mm
Exhaust : 0.15 to 0.20 mm
Valve recessing : 0.19 to 1.1
Decompressor valve clearance : 0.75 to 1.12mm

PISTON RINGS
Piston ring gap :
Piston top compression : 0.15 to 0.30
Intermediate : 0.30 to 0.45
Oil control : 0.30 to 0.45

CYLINDER HEAD
Cylinder head surface flatness : < 0.05mm

SEA WATER PUMP
Water flow : 2.2 l to 10 l

GLOW PLUGS
Resistance :

--------
Maintenance items
Oil Levels (Engine & Gearbox)
Battery Charge (indicator)
Water Temperature & Operation
General Sealing
Battery Electrolyte level
Operation of the Controls
Belt Tension
Valve Adjustment
Starter & Alternator Mountings
Tightness of Screws and Assemblies
Sea Water Pump
Engine Mounts and Alignment
Injector Calibration
Sea Water Strainer
Thermostat (to be cleaned)
Coolant level in Heat Exchanger
Zinc Anode
Air Filter
Heat Exchanger Tube Stack
Oil Filter
Fuel Filter
Oil (Engine & Gearbox)
Coolant
Primary Fuel Filter
O-Rings, Heat Exchanger
Impeller
V Belt

Part Numbers
Oil Filter 493150
Fuel Filter 622350
Impeller 434013
Gasket, Impeller 504028
Seal, W/Pump 434031
V Belt 037335
O-Ring, Heat Exchanger 604617
Anode, Engine 494635
Anode, Selva Sail Drive (<2003) N/A

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23 minutes ago, Kevin McCready said:

But I can't figure out which fuel line or lines we're talking about.

Here you go Kevin.  In flow direction order:

Blue is from your primary fuel filter / water separator to the lift pump.

Red is from the lift pump to the secondary filter.

NOTE: the picture is not clear and these two may actually be the other way around where they connect to the lift pump 

Orange is from the secondary filter to the injector pressure pump

Green is the return line to the fuel tank

Yellow is the fuel return from the injectors to the outlet of the secondary filter.  Its there mostly to allow air bleed.

kevins fuel system.jpg

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It is really important to get intimate with how the Fuel system works. Whenever it doesn't work, it is usually at the least opportune time. Like it might be ruff and the last pace you want to be is head down in an engine compartment. So knowing what to do is important so you can spend less time there in an emergency.

Lets start at the injectors and work backwards. The injectors are the two things that are screwed into the top of the Head and have two steel tubes running around and down to the Injector pump below. The injector on the left has a black hose coming out that has SAE100-6 stamped on it. That is the return line and you will see it goes back to a white filter. The white filter is your Final Filter. I will call it that because I have found people call it either Secondary or Primary. The important point is, it will be a very fine Micron rating and is the last line of defense before fuel enters the Injector pump. 
The reason why your return line is fitted to that is due the being only a very small amount of fuel ever going back through the return and it is quite acceptible to join into the fuel system at this point. The fuel just goes round and round the sytem.

Just out from the point where the two metal lines fix to the IP, you will note a flat piece of the pump leading your eye out to a fixing that has two braided Fuel lines and a rusty looking Nut on the end of them. That will be the bleed point for the injector pump. 

Below that is a round looking component. Directly mounted to the left hand side of that are two braided fuel lines. This is the Fuel Lift pump. One of those fuel lines is the in line, coming from what I call your primary filter, which is the filter with the Glass bowl. The other is the out line and should run to the Seconday Filter, being the White one.

  On the left hand side of that round lift pump is a little flat lever. That should be the fuel priming lever. That should suck the Fuel through from the glass bottom filter and push the fuel up into the white filter and on to the Injector pump.

The item that has the rubber crinkly boot will be either the Throttle, the stop, or in some cases it can be both. As already said, it mov es the Fuel rack inside the Pump and that rack position determines the amount of fuel the Injector pump will push into the Injector. So in some cases, the throttle can also pull the rack hard back and stop fuel delivery to injector and thus stop engine.

How to bleed. Especially if Tank has run dry, or the filters have just been changed.
In an installation like this, it is likely that the Fuel tank/s are above the level of the first filter. You need to turn off a fuel valve at the tank when you want to replace the filter if that is the case, or fuel will run out while the filter is dismantled.
Another way it can be done is that the tank might be below filter level and no fuel valve fitted. This requires a slightly different means of priming.
The filter at this point is a very commonly used CAV filter housing. Now also available by a couple of other brands. This one uses a cheap element that is easy to get and you should keep a few of these as spares and stored in an easy to get to place. It tends to be the main filter that will cause blockage problems from dirt and Bug etc.
 We will assume you have just replaced the Filter.
a: for tank above Filter, simply loosen the bleed screw on top of the CAV housing and wait for fuel to flow clean of any air bubbles. The bleed screw is the one that sits up proud of the other, which is a long bolt that runs through the Filter and pulls the Bowl up tight against the element. There will be a rubber ring between Bowl and element a element and top housing. Don't over tighten bolt when pulling back up.
b: tank below filter, you will need to leave the bleed screw closed and use the lift pump to pull the fuel through the filter. You need to open the bleed nut on the Injector pump and then manually pump fuel through. When that CAV filter is full, you can then losen the bleed nut on top of the housing and let any bubbles out. DO NOT pump. When no air is present, close that CAV filter bleed nut.

Now continue to pump the fuel on through the next filter till fuel comes out that Injector Pump bleed screw. Once all the air bubbles have stopped, you can close that bleed point off as well.

You can try starting the engine at this point.
(For any Diesel that has a Rotary Injector pump, they self bleed and you do not usually need to crack and injector.)
For any inline pump, which this one is and tend to be the most common found, they require the injectors to be cracked. This means that you will require a spanner that fits the nut on the metal line at the injector. You undo the nut just a little. It takes some force to undo it and it usually goes with a crack, hence the term. While turning the engine over, the air and fuel will bubble out and the engine will start and perhaps run rough. Once the engine starts, tighten that nut and it should run sweet. You usually only need to do this to the one injector. If the engine still runs a little rough, you could try the other injector, but that is usually not needed.

If you do not bleed the air out, the engine runs in the exact way you were describing. It takes quite a lot of time to get that air bubble to finally push it's way through. That is because air compresses and the amount of fuel going into the injector is really tiny. So the air bubble will be bigger and simply compresses not allowing the fuel to get pushed into the injector and overcome the spring pressure of the injector seat. The Injector has a needle under a very high load spring and the Fuel pressure must overcome that load and lift the needle and then the fuel sprays out in a very fine mist.

Keep a clean dry rag with you at all times and you can use that to stop fuel from dribbling down and keep your tools and hands clean and dry. Which dramatically helps holding onto the Tools.

I hope that is helpful
 

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^ "and that, folks, closes today's Diesel 101 session.

There will be a test tomorrow - please make sure you bring two pens, a 27/64" ring open-end spanner, and eye protection."

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A lot of Marine diesels don't bother with an air filter as there is a shortage of (no) dust when you are out at sea, unless you are sailing close to the Sahara or somewhere similar. You can certainly fit one if you choose, but I think?? your air pickup isn't designed for one.

It certainly wont have any effect on your current problem.

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Sorry to add to your list of woes but the picture of the water bowl looked suspiciously like it had some diesel “bug” in it or it could just be a rust stain ?  I had a year of pain with my bulldozer and the bug so would highly recommend putting some biocide in the fuel tank to be sure . 

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12 hours ago, Steve Pope said:

A lot of Marine diesels don't bother with an air filter as there is a shortage of (no) dust when you are out at sea, unless you are sailing close to the Sahara or somewhere similar. You can certainly fit one if you choose, but I think?? your air pickup isn't designed for one.

It certainly wont have any effect on your current problem.

Very true. The problem is that the Paper Air Filters get very damp and clog. I used K&N Filter on my boat motor. That worked well. I liked the idea of something that could stop any larger item from every being sucked in. Like a small piece of Foam or rag.

Do not confuse a box that looks like it should have a Filter, with a resonator Box which can aid in the reduction of the droning noise that can come from the intake.

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Use the Biocide called "Drain" :-) .
Water always looks bad in a filter. Drain it and simply keep and eye on it. It is something we should all do before going out.
But if you do want to use an additive, any of them will work. I use one from Supercheap or sometimes the Lucas one from BNT.

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Just a small point which might help some. When you  have to prime the system, the little lever on the side of many lift pumps is a] a b....y pain to get at, and you often find that you have to pump and pump and.... to get enough fuel through. We've fitted an outboard squeeze pump into the line from the tank and this really helps get the fuel through and started.

In addition, I'd add my thanks to all the detailed advice you gave. We should cut and paste it into an article for later.

 

 

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When do you actually use the pump primer other than resetting after new filters? Maybe it was my pushing it a few times rather than the ether which did the job. Sorry to my mentors if I just failed the Diesel 101 test.

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1 hour ago, Kevin McCready said:

When do you actually use the pump primer other than resetting after new filters? Maybe it was my pushing it a few times rather than the ether which did the job. Sorry to my mentors if I just failed the Diesel 101 test.

from experience, when you are dead in the water 300m off the river entrance at Clevedon in a howling NE gale on a rising tide...

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3 minutes ago, aardvarkash10 said:

from experience, when you are dead in the water 300m off the river entrance at Clevedon in a howling NE gale on a rising tide...

Did you suddenly have fuel problems and have to fix it?

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Normally only used after changing the filter or cleaning the water trap, usually, as aardvark says, when things have turned to custard in unpleasant conditions.

Often on a yacht that is used infrequently, there is a build up of detrius in the fuel tank, this usually becomes apparent when it is all shaken up in the conditions he mentions, (murphys law) and you have had to install a new filter etc etc.

Invairiably it is the same time your wife / partner realises she has been conned, and she becomes certain that she can find better things to do whenever you suggest going for a lovely romantic cruise!!!

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