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730D knock knock what's there?

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scottAR

03-21-2003 19:45:27




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Pulling water furrows today with my freshly overhauled 730D and it started a high up in the cylinder knock after running about an hour. Slowed the motor speed and it quit knocking. Went to another field and it started doing it again at all speeds. This time started getting some black smoke. Cranking it with the decompression pedal depressed reveals no knock. Is this a valve, injector, rod bearing or what?

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scottAR....correct diagnosis...Thanks!

03-22-2003 18:15:34




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 Re: 730D knock knock what's there? in reply to scottAR, 03-21-2003 19:45:27  
Worked on it a little today and found that one injector had a bolt in it that was too long and was bottoming in the hole. This let the injector jump up and down. The tip was not damaged but after testing it with my 40 year old injector tester, I found the opening pressure was too low. These injectors were renewed last year so I am assuming the damage came from running loose. I hope that is my only problem. The valve train looks good as do the rod bearings. I am just trying to keep from pulling the head off again. Thanks

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will

03-22-2003 19:46:45




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 Re: Re: 730D knock knock what's there? in reply to scottAR....correct diagnosis...Thanks!, 03-22-2003 18:15:34  
Glad you found your problem. One other thing to look for is the injector hold down clip. Sometimes they have to have the peg that sets against the head ground down to allow the injector to go in far enough to seal. I hope the injector tube didnt get burnt on the end due to the exhaust passing by the injector. If your injector is not below 2300 it will most likley run for a long time. If it is much below that Maybe a replacement is in store. One of mine only checked 2350, but it starts and runs great. The best of luck. Let us know how you come out.

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scottAR

03-23-2003 12:46:40




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 Re: Re: Re: 730D knock knock what's there? in reply to will, 03-22-2003 19:46:45  
I couldn't stand it. I had to go check the other injector before church this morning and both of them do not snap and chatter like I think they should. If you pump it slow they put out six straight streams. If you pump it fast they atomoize but it puts out fuel the whole stroke which looks like to me is way too much fuel. And the oil is over full on the tractor for the short time it has run. I'm going to send the injectors to a different shop tomorrow.

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will

03-23-2003 14:02:46




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 Re: Re: Re: Re: 730D knock knock what's there? in reply to scottAR, 03-23-2003 12:46:40  
A diesel shop can keep a constant solid pressure on them, and figure out just exactly at what pressure your injectors open, which is what you want to know. Remember just because it looks as if it is putting off a lot of fuel does not mean that the rack supplies as much fuel as your tester does. The bore and stroke of the rack are most likley not as big as your tester, so they could not possibly put off as much fuel. As for fuel in the oil, the injector slobber tubes go right into the oil ports of the head, so the excess fuel goes straight to your crankcase oil. With the way it sounds you very well could have a defective injector. Hope you got all that diesel fuel smell off your hands before church. My mom can smell it at the other side of the church building. No matter how many times you wash your hands they still have a hint of the fuel. Be sure to check those hold down clips before you put you tappet cover back on. The clips may be part of your problem. You stated that your bolts were too long. My head has studs with nuts to hold the injector clips rather than bolts. Perhaps to make sure you are not bottomed out you could replace the bolts with studs, so you could see if you were bottomed out or not. Just a thought. The best of luck!

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scottAR...diesel on hands!

03-23-2003 17:58:56




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 Re: Re: Re: Re: Re: 730D knock knock what's there? in reply to will, 03-23-2003 14:02:46  
Yes you were right again. I was in the choir and during the anthem I smelled diesel. The guy next to me is a superintendent for the Park Service. I doubt if it was him that smelled like diesel on a Sunday morning.



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F-I-T

03-23-2003 15:41:14




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 Re: Re: Re: Re: Re: 730D knock knock what's there? in reply to will, 03-23-2003 14:02:46  
Will:

I'm confused. I thought those leak off tubes ran to a port that routed that excess fuel to be the injector bracket to be re-pumped. Now I could be wrong here, but I want to understand this.

If the leak off was just supposed to vent to the crankcase oil, wouldn't they just let it drip out into the valve cover which would drain to the crankcase ?

Why bother with the leak off tubes ?

I really want to understand this.

Thanks !

Frank-in-Tallahassee
70D // 855

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will

03-23-2003 18:44:08




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 Re: Re: Re: Re: Re: Re: 730D knock knock what's there? in reply to F-I-T, 03-23-2003 15:41:14  
I will attempt this, and if I get it wrong maybe someone will correct me. The injectors only has two lines. One is a high pressure input line, and the other is a slobber tube. It is only about 6 inches long in total length. I dont know If you have ever had a 2cyl injector off or not, but one of the line is short, and only bends into a port in the head, and then it is cut off flat, which allows it to drip into the oil returning to the crankcase from upper engine lubrication. I may not have made myself clear in my post above, and for that I apoligize. Im not sure for the reason of not letting it just drip into the valve cover. Seems to me as it would have been the same thing, as it ends up in the same place a few inches down stream, but maybe Deere had a reason!! As far as I know the only return is from the rack. There is no return on the injectors, only an imput and slobber. I hope all of this is correct, and if it is not I am sure someone will correct me. Glad you are interested.

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F-i-T

03-23-2003 19:23:48




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 Re: Re: Re: Re: Re: Re: Re: 730D knock knock what's there? in reply to will, 03-23-2003 18:44:08  
Will:

I rebuilt my 70D last year, rebore, pistons, pumps, the whole shebang, so I feel pretty familiar with the inner workings of the 2 cylinder diesel.

Reason I ask is that I do not remember that there is a port on the block side of the head for that fuel to drain into and on to the crankcase. I was pretty sure that the "slobber" or leak off lines went into the head and that the fuel that entered that port could be recycled. Conventional diesels do this with a leak off line back to the pump.

I have looked at my pictures of the block, head, and head gasket, and I can't see that there is a way for the excess fuel to get to the crankcase.

I really need to understand this....it's more than a casual interest. We never had a diesel get an inordinate amount of diesel in the oil, unless through a bad fuel transfer pump. I would guess that since any injectors can "slobber" then they all would have fuel in the crankcase. I have never seen this as a normal occurrence on the 6 or so diesels I have worked around on the farm and later in rebuilds.

Do you know of any book where I can see this, because from the block side it does not look that way.

Not pickin' a fight, but I really need to know this for sure, because if it is true, I might have to tear something down.

Frank-in-Tallahassee
70D // 855

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will

03-23-2003 19:44:16




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 Re: Re: Re: Re: Re: Re: Re: Re: 730D knock knock what's there? in reply to F-i-T, 03-23-2003 19:23:48  
I dont think you need to tear anything down. If you were getting fuel in your oil it would be over-full. When I say port in the head it is the same one that lets the oil from upper engine components drain back to the crankcase. On most other diesel engines the return is located on the injectors, and the excess fuel is returned to the tank. My only experience is with a 730D. There is a good posibility of slight design difference. On a 2cyl the injector will not slobber unless it has malfunctioned inside, because the rack gives it only what it wants, so there is nothing to slobber as on a modern day pump that does not return, but rather lets the injecor do it. The unwanted fuel from the rack is sent back to the top settlement bowl on my tractor. It is important to realize that the return is not on the injectors, but on the rack. I think that must be what you are missing. perhaps you are used to seeing the injector having the return. 2cyls do not. 2cyl JD does have a strange fuel system, but is did hold up, and It helped them to set a fuel record that they held for 38 years. I find that pretty impressive. I am sorry that my post are confusing. What sounds good to the one writing often does not sound good to the person reading. Feel free to email me if you would like, as not to take up room here. I hope maybe this will clarify my earlier statements.

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F-i-T

03-23-2003 20:33:30




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 Re: Re: Re: Re: Re: Re: Re: Re: Re: 730D knock knock what's there? in reply to will, 03-23-2003 19:44:16  
Ah, see, I don't think the 70 and early 720 D's had a return line from the pump bracket back to the sediment bowl (from what I can see in the parts book). I know my 70 has only one line from the sediment bowl to the fuel transfer pump, to the filters, to the right hand side of the block to the fuel pump bracket and rack.

I've owned a lot of other diesels, and of course they had injector return lines. That's why I asked.

I did have a crankcase of fuel this weekend after returning from a week long trip, and the tractor sitting still. It has not done that in the first 100 hours since the rebuild. I had the fuel transfer pump rebuilt as well as the pumps and injectors.

Tractor runs fine. Now I'm leaning toward failed seals in the fuel transfer pump, but after that few hours, I want to understand if there is any other possible cause.

Frank

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will

03-23-2003 21:01:30




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 Re: Re: Re: Re: Re: Re: Re: Re: Re: Re: 730D knock knock what's there? in reply to F-i-T, 03-23-2003 20:33:30  
I cant remember the exact track for my fuel lines. Been a while since I did any fuel work, and I hope I dont have to do anymore. I just remember the return line comes from the top of the rack through the rack cover plate, and goes to the top of the sediment bowl. I am at school a few hundred miles from home, so I cant go look at it to tell you the exact route of the lines.



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Clooney

03-22-2003 08:59:16




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 Re: 730D knock knock what's there? in reply to scottAR, 03-21-2003 19:45:27  
Scott, it could be fuel related per G-Man & Will below. See if you can tell if it's once per revolution [every revolution] if so it's probably not injection related but more than likely mechanical. If it's every other revolution it could be fuel related but could also be a firing pulse induced knock like loose clutch driver or loose flywheel. ~Have you re-tightened the flywheel since the overhaul? If not, start there, those flywheel bolts should be checked a few times after installation as they sometimes loosen as the flywheel seats on the splines. If you re-used the original flywheel bolts there is a good chance they were stretched during their lifetime & won't hold a torque. ~Any chance there was some gasoline put in the fuel tank [by mistake]? If so that will cause a knock.

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G-MAN

03-22-2003 05:23:32




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 Re: 730D knock knock what's there? in reply to scottAR, 03-21-2003 19:45:27  
A diesel that's knocking and producing black smoke at the same time generally indicates some sort of fuel system problem. Could be that the injector isn't firing right, or is injecting to much fuel.



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will

03-22-2003 08:15:22




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 Re: Re: 730D knock knock what's there? in reply to G-MAN, 03-22-2003 05:23:32  
to add to what GMAN says. If and injector is causing this problem you could possibly have large amounts of diesel in your crankcase oil. Sounds like maybe an injector is just dumping. Opening pressure should be around 2600 psi. If the opening pressure is too low the injector cant hold back the fuel until it has enough pressure to make a mist, so it just drips. Dont run your tractor anymore than you have too. This excess amount of fuel will wash the oil from your cylinder walls that lubricate your piston rings. If you had your injectors' opening pressure adjusted when you rebuilt your engine, for sure suspect injectors as your problem. Usually adjustments cause problems. Just get a completley rebuilt one. your local diesel shop should be able to check you opening pressure and spray pattern. Mine does it for free, so most likey your wont charge too much.

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