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Old 24-01-2011, 18:24   #1
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3GM30 Fuel Injection Pump Question

Does anyone know how the distribution of the injection pump works?

I have looked at manual after manual and none seem to describe the workings of it. A few of the manuals show the fuel injector camshaft which appears to be attached to the camshaft, but it only has one cam on it. For a 3 cylinder engine, i would expect 3 cams one for each plunger. Or do you think they dont show all the cams because they are implied with the diagram.



Thanks a bunch for any thoughts on this, im just trying to better understand this system.

austin
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Old 24-01-2011, 18:36   #2
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Does anyone know how the distribution of the injection pump works?

I have looked at manual after manual and none seem to describe the workings of it. A few of the manuals show the fuel injector camshaft which appears to be attached to the camshaft, but it only has one cam on it. For a 3 cylinder engine, i would expect 3 cams one for each plunger. Or do you think they dont show all the cams because they are implied with the diagram.



Thanks a bunch for any thoughts on this, im just trying to better understand this system.

austin

The fuel injection pumps along with governors are the two items that are really best left to the experts to fix.
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Old 24-01-2011, 18:44   #3
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I'm not trying to fix anything, im just trying to educate myself a bit on the system that I have and diesel engines in general...

But that could be why so much seems left out of the manuals.

thanks
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Old 24-01-2011, 18:59   #4
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I'm not trying to fix anything, im just trying to educate myself a bit on the system that I have and diesel engines in general...

But that could be why so much seems left out of the manuals.

thanks

OK I understand that. I know that many manuals leave out a lot of information that would be really nice to be included. My Yanmar manuals ($80) leave out a ton of info. No money in it for Yanmar if you fix everything yourself.
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Old 24-01-2011, 19:17   #5
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Good point.

thanks again.
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Old 24-01-2011, 20:34   #6
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I have this engine, fresh water version. Also a factory manual on board (though I'm not). I was reading about this last time on the boat, but I can't remember the details. It was simple to understand.

I'm going to the boat in two days. So I'll post again then if nobody answer before.

My questions......

Does a diesel injector pump do the following,
1. pump fuel to a higher pressure than the lift pump? I vote yes.,,, and
2. distribute fuel to the injectors? of course.

The cam could be what drives the pressure of the injector pump.
I recall a pushrod or rack? that controlled volume delivered, I think.


Sorry, I'm just thinking out loud, and I'm interested in learning diesels.
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Old 24-01-2011, 20:40   #7
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That picture looks like it's out of the Haynes manual. It covers 1, 2, and 3 cylinder GM engines. It repeats information for the multicylinder engines where it is needed.

I don't think the manuals are hiding stuff to make you use mechanics, especially 3rd party manuals. Manuals assume you are a mechanic or have enough experience to figure basics out. There are other books dedicated to teaching how to repair engines in general. They don't have the exact details as to which part has to come off first, where the bolts are hidden and what torque is needed.
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Old 25-01-2011, 08:53   #8
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I have looked at manual after manual and none seem to describe the workings of it. A few of the manuals show the fuel injector camshaft which appears to be attached to the camshaft, but it only has one cam on it. For a 3 cylinder engine, i would expect 3 cams one for each plunger. Or do you think they dont show all the cams because they are implied with the diagram.
There are 3 fuel cams on the front of the cam shaft on a 3gm30, one for each plunger in the injection pump. See picture from the Yanmar Service Manual.

FWIW, if you decide to remove the pump for servicing, on reassembly, make sure you have the pin on the fuel rack properly seated in the governor lever. There is an inspection hole with a plate that allows you to verify. Check it, double check, and triple check! Have someone move the shutdown cable while you're watching. This is the only control on the engine, throttle and shutdown! If it's not connected, there is a good chance the engine will run away and blow upon initial startup.
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File Type: pdf 3gm30-cam.pdf (265.4 KB, 164 views)
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Old 25-01-2011, 09:15   #9
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Does anyone know how the distribution of the injection pump works?

I have looked at manual after manual and none seem to describe the workings of it. A few of the manuals show the fuel injector camshaft which appears to be attached to the camshaft, but it only has one cam on it. For a 3 cylinder engine, i would expect 3 cams one for each plunger. Or do you think they dont show all the cams because they are implied with the diagram.



Thanks a bunch for any thoughts on this, im just trying to better understand this system.

austin
A manual won't explain the theory, a text book will. Mine is called "Diesel Technology" by Norman/ Corinchock (seventh edition). It is pretty comprehensive. There are many others out there and if you are keen to learn the basics of diesel theory and operation they are a good investment.
The local Library may be a good place to start.
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Old 28-01-2011, 12:42   #10
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theway,
The picture is for a two cylinder setup. Notice it has two pairs of intake and exhaust lobes on the engine camshaft. Hard to tell, but it has two cam lobes on the fuel cam. I'm looking at the factory manual now with pictures of all three setups for 1, 2, and 3 cyl. engines. DotDun's pdf shows a three cyl. fuel camshaft.

I thought the fuel injection pump would rotate but it turns out it plunges instead. Only the fuel camshaft rotates.




theway asked,
"Does anyone know how the distribution of the injection pump works?"

I say,
One fuel cam lobe per cylinder operating a plunger/delivery valve in "time" with an associated cylinder. This pressurizes and times a fuel pulse. Then the throttle lever operates the fuel rack and pinion to change the size of the fuel intake hole to the delivery valve. And this adjusts the volume of fuel delivered in a pulse, which passes through the pipe to the injector nozzle.


That's the way it looks to me.
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