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Old 25-07-2016, 12:40   #16
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Re: answer me this, if you will....

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Originally Posted by zeehag View Post
ok so how does one go about splaining why the machine restarted so easily--- it has excellent ability to maintain prime... but is that enough to re start this ??
You got one great sealed system. Means also your piston rings are as good as new. If you got a decompression lever, try releasing it to see what happens. If my theory is correct, it will not start after you do that(and of course resetting it).
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Old 25-07-2016, 12:52   #17
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Re: answer me this, if you will....

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ok so how does one go about splaining why the machine restarted so easily--- it has excellent ability to maintain prime... but is that enough to re start this ??

Maybe your new engine is using so much oil it can start on that.
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Old 25-07-2016, 12:54   #18
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Re: answer me this, if you will....

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Maybe your new engine is using so much oil it can start on that.
for a change i am not using nor making oil in my machine yaaayyyyy... but when shiit happens, it does so in 3s.....and this damnboat can count.. i love it....
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Old 25-07-2016, 12:56   #19
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Re: answer me this, if you will....

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Maybe your new engine is using so much oil it can start on that.
That is theoretically possible, but need really worn rings.
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Old 25-07-2016, 12:59   #20
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Re: answer me this, if you will....

Surging is usually not enough fuel flow. Have you checked your tank vent fittings? bugs plug them sometimes creating a vacuum.
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Old 25-07-2016, 13:02   #21
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Re: answer me this, if you will....

cheechako--tank vents are ok and functioning well.. but i had zero fuel pump --except the injector pump-- functioning when i was misadventuring to ge there--i am astounded this was able to occur--by all rights i should still be bobbing on the pacific ocean prolly in chile swearing at the mechanic who refused to rebuild manual pump.

oh yeah an di wondered why i got such excellent fuel mileage-i shoulda had almost none left, but i ended up with 100 liters in reserve... i am totally blown away, as i usually drift in on fumes and not much else.....(no. i still suck at math)

now i only have 120 or so hours on my engine... is brand newly rebuilt, ka lunk.....
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Old 25-07-2016, 13:22   #22
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Re: answer me this, if you will....

The injector pump will pull fuel to some extent, it is not uncommon for a lift pump to fail and the engine will run, and sometimes sag in RPM and sometimes surge, and sometimes run normally. Side note, I think that is what is going on with my generator I get maybe 20 hours then it begins to sag in RPM and I have to change the fuel filter, I believe my lift pump is inop. But I have not bothered to trouble shoot it yet, waiting on parts.
If it was a PT-6 aircraft turbine engine your allowed to accumulate I believe 50 hours with an inoperable boost pump, then you have to replace the high pressure pump cause it may have been damaged by cavitation, 100 hours on the new GE H-80 engine.
Now these are not aircraft, but the principle is the same.


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Old 25-07-2016, 13:42   #23
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Re: answer me this, if you will....

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Was referring to the engine's pistons. Basically sucking in the fuel, and with a closed fuel line(it is closed, right?), would be able to self feed. Had an old Singer roadster(it was old when it was new) that ran on that principle, or did not run as the case may be. Hand crank the engine to get the fuel moving.
Pistons can not suck fuel in on a diesel engine. Fuel is squirted into the cylinders under very high pressure by the injector system.
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Old 25-07-2016, 13:59   #24
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Re: answer me this, if you will....

Stop l00king in the gift horses mouth........ get on & ride!
Buy a lottery ticket..... Too late horse has bolted.....

Nah, I'm with the injector pump pulling.
I have rebuilt my 3gm30's fuel system & it is randomly hard/easy too start.
Damned if I know.
But it doesn't surge once going.
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Old 25-07-2016, 14:05   #25
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answer me this, if you will....

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Pistons can not suck fuel in on a diesel engine. Fuel is squirted into the cylinders under very high pressure by the injector system.

They could in theory, except there is a pretty significantly high cracking pressure on injectors, way higher than you could get with a vacuum, which is only 14.7 PSI. So no, even if they could pull a perfect vacuum, it's still not nearly enough to open the injector and pull fuel from it.


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Old 25-07-2016, 14:17   #26
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Re: answer me this, if you will....

[QUOTE=a64pilot;217457
Now these are not aircraft, but the principle is the same.



They are not even close to the same, not even in the same world. The Cav pump on a Perkins uses 2 plungers operated by a cam.
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Old 25-07-2016, 14:19   #27
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Re: answer me this, if you will....

I agree with a64pilot. Under ideal conditions, a diesel engine will run with the injector pump alone. It's not healthy for the injector pump to do the low pressure work as well, so I wouldn't recommended it.
An injector pump is not designed to pull a big vacuum, the fuel lines would have to be perfectly purged of air to start and continue running. Any hint of air in the lines would make it impossible to start.
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Old 25-07-2016, 14:43   #28
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Re: answer me this, if you will....

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Pistons can not suck fuel in on a diesel engine. Fuel is squirted into the cylinders under very high pressure by the injector system.
Absolutely correct.

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Old 25-07-2016, 14:57   #29
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Re: answer me this, if you will....

It's a good thing these boats have sails because some people don't know squat about diesels. There is no vacuum. You need a throttle plate to have a vacuum. A diesel is wide open. It takes about 16,000 psi to open an injector the right way, you can't open it the wrong way.
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Old 25-07-2016, 15:31   #30
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Re: answer me this, if you will....

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It's a good thing these boats have sails because some people don't know squat about diesels. There is no vacuum. You need a throttle plate to have a vacuum. A diesel is wide open. It takes about 16,000 psi to open an injector the right way, you can't open it the wrong way.

No, a simple mechanical injector cracking pressure is I believe around 120 bar or about 2000 PSI. It may be lower than that on the older designs, I don't know. Injectors are one of those things I have serviced, I just R&R them.
Common rail systems fuel pressure will run in the tens of thousands, my Duramax runs I believe about 30,000 PSI stock, it is largely the magic that makes common rail as good as it is, you can get lots more fuel in the engine in less time allowing higher RPM etc.
Of course a Diesel has no vacuum, it has no throttle valve, actually it has some vacuum, it's measurable as air has mass, but it's trivial and for all intents no vacuum is correct.
A spark ignition engine is throttled by varying air and fuel together keeping hopefully a stochimetric (sp?) ratio, Diesels only vary fuel, they pull in a full amount of air regardless of load, operating very lean like that is one reason for their efficiency


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