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Old 11-08-2008, 20:35   #16
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Thanks for the replys. It took long enough but it appears to be two problems. Too much fuel getting delivered and a gasket problem on the turbo charger.
All should be well soon.

Thanks again for taking the time to answer.
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Old 11-08-2008, 22:03   #17
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Which gasket was it?

How was the fuel delivery problem found?

(Waiting with 'bated breath)
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Old 12-08-2008, 05:18   #18
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If its just a puff..there could be a partial blockage in the exhaust elbow...Yanmars are famous for it..it will get worse and I have had a 3gm start, run a while whilst spitting fuel and fumes out of the air intake..only to slowly die and stop. The mixing elbow was partially blocked.
Try removing the elbow, flushing through with Muriatic acid re fit and try...if it makes no difference then you have lost nothing but can discount the idea.
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Old 13-08-2008, 11:54   #19
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The various shade tree mechanics here have all delivered their thoughts and recommendations. But the smoking is gone after some tweaking. I had a visit from some real deal mechs finally and I expect the engine will be well and provide many more years of reliable service.
The plan to replace the mechanical fuel pump and plumb it along with the electric pump. At present I am running only on an electrical pump. If I lose 12 volts the engine stops running from fuel starvation.
Once the new pump is installed should I put a switch on the electric pump so it only runs when I want it on or leave them both operating?
If the engine is working good with the mechanical pump it seems silly to have the other one going as well.
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Old 13-08-2008, 12:02   #20
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I cant see the need for two pumps...if the mechanical is good .use that. You can always jury rig the electric if you need to. What was the tweaking you mentioned. All this info is always usefull..
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Old 13-08-2008, 17:33   #21
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Use the mechanical pump only.

Plumb the electric pump to either fill your filters or act as an emergency fuel pump.

There is no need to use both.
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Old 13-08-2008, 18:16   #22
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Thanks Chief

Stupid question here. Does it matter where the electric fuel pump is in line. Meaning if it was between the filters and the tank would it push enough fuel to run the engine if the mechanical fuel pump failed.

When not energized will it allow fuel to pass through when only using the mechanical pump.

I freely admit that even with all the reading I have done I am still somewhat in the dark on this system. Fortunately all my missteps and mistakes have only cost me money so far.
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Old 15-08-2008, 02:56   #23
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This does depend on the particular engine. There is a danger of using an electric pump with the mechanical in the line still. If the Diaphragm of the mechanical ruptures, you force fuel into your sump. As already stated, no need for two at the same time. But you could plumb a set of valves that can over rule the mechanical and bring the electric in as a back up, or vise versa, if you so wish. Depending on the fuel filter, some will take pressure, some will not, so check which type you have.
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Old 15-08-2008, 07:36   #24
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Alan, You have now confused me, which is not hard to do, since we have used an electrical pump on two engines now, one Perkins, one Yanmar. If the pump pushes too much fuel it just goes back to the tank via the return line. How would it push it into the sump?
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Old 15-08-2008, 08:24   #25
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As Alan says, if the mechanical fuel pump diaphragm gets a hole (crack) in it (most common failure mode of mechanical pumps) the electrical pump will push fuel into the sump.
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Old 15-08-2008, 14:13   #26
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Quote:
If the pump pushes too much fuel it just goes back to the tank via the return line.
Nooo no no no....well maybe.....it really does depend on the Injector pump. But in most of the everyday systems most of us have on our boats, the low pressure side, that is the fuel pump taking fuel from tank through filters and pushed on to the Injector pump, does not get to flow down the return side to tank. The return to tank is from the high pressure side of the pump. The side that feeds the injectors.
When you start getting into large engine installations, the IP can return a flow to tank for IP cooling, that comes from the low pressure side of the pump. The most common systems that we will come across will not have this. It is easy to check which you have. If it is the the more common install, there will be only one small tube connecting each injector together and then that little tube will run off to the tank, or some T'ee into the low pressure fuel supply line. This little return line is bleeding fuel left over from the Injector after it closes.
If you have a pump cooling return line, that will come from the body of the pump it's self and returns a high flow rate of fuel.
The new high pressure common rail engines I can't speak for. I haven't had the pleasure of playing with one of those yet.
The way fuel can get into the sump is due to many of the mech pumps designs. The way the mech pump works is, it has a lever that rides a cam. The cam is often on the cam shaft, but this can vary. The Cam shaft is usually exposed to the sump as it is usually inside the Cast block. Overhead cam is different of course, but most of our diesels are not overhead cam. The lever on the pump pushes the diaphragm back and forth which with a couple of little valves, creates the sucking and pushing action. If a hole or tear forms in the diaphragm and the fuel to the mech pump is under any pressure, fuel will be pushed right through into the sump. It is not common, as in the diaphragm will work for many hrs, but it's possible failure is mostly the reason why people fit electric pumps in the first place.
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Old 27-08-2008, 13:51   #27
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3GM30F Heat exchanger and /or wet exhaust problem

Ive been sailing my boat pretty solid over the last year and havent had much time in marinas. The Yanmar 3GM30F started smoking - white, but also black at high revs in reverese. The volume of the oil increased but did not have the milky color or droplets. I discovered that the exhaust elbow had cracked and was not poperly exhausting. After fixing that, Im now having problems with adequate water flow in the exhaust and the engine begins heating after running at load.
I drained the wet exhaust, replaced the impeller, tensioned the belt, verifed that the water pump works and checked the raw water flow all the way past the water pump.
I opened the front of the heat exchanger and there was evident corrosion on the inside of the front cap and inside the tubes.
I reamed the tubes out gently with a plastic covered wire. There was noticable resistance at the end, but nothing requuiring heavy preassure to get break through.
I dont know what the back looks like on these exchanger tubes and hope I didnt punch through the metal. The front cap looks like the fresh tubes are isolated from the salt by a gasket- which is slightly corroded.

Im ready to sail another few hundered miles and wonder if Im taking teh proper approach.

1) Do I have a blown head gasket? Ive done several oil changes and havent seen the increase or other indications of moisture since the elbow was replaced. I havent ran the engine very long due to the wet exhasut issue.

2) Have I damaged the heat exchanger with the ream out?
3) If tehre sia slight breakthrough on the inside of the heatexchange front cap, will this casue more problems?

Thanks for your help- Im running out of time.
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