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Discussion Starter · #1 · (Edited)
Firstly, let me say I have searched fairly thouroghly for related posts, but no joy. So I need to have the injection pump rebuilt on a John Deere 4320 with the 6.6L diesel. I have been told that when I get the pump back it will be set to TDC (Top Dead Center). So, it seems to me that the best course of action is to set the engine to TDC prior to removal of the failed pump. My question is, what is the best method to determine TDC on this engine? I have included a photo of a couple of covers on the engine that I think might be used in the process, but I really have no idea.

Edit: This is a '72 4320 with the 6.6L
 

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Welcome to GTT!

I'm not super familiar with your tractor or engine, but I'm thinking there's a timing pin or mark on the flywheel or front crank pulley. If all else fails and you don't have a tech manual, you can always use the valve method.

Remove the valve cover. Setup a pointer on the front crank pulley. Rotate the engine forwards until the #1 cylinder intake valve is closing. Setup a dial indicator on the valve. When the valve fully closes and zero the dial indicator, rotate the engine backwards until it reads .050. Mark the crank pulley. Then set the dial on the exhaust valve. Rotate the engine forwards until you read .050 on the dial. Mark the crank pulley again. Split the difference between your two marks, that should be TDC. It works on most diesels.
 

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There should be a TDC mark on the flywheel, the problem is that you don't know if you're on TDC for #1 or #6. Since 1 and 6 are companion cylinders you have to pull the valve cover to see which cylinder you're on. The easiest way is to read the valves. If you watch them as you're turning over the engine you'll see exhaust valve on one closing and then intake open. That's how you know that cylinder is on TDC. You'll have it just about dead on when both the intake and exhaust valves are tight (you can't wiggle the rockers back and forth) and the rockers on 6 should be loose.
 

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There should be a TDC mark on the flywheel, the problem is that you don't know if you're on TDC for #1 or #6. Since 1 and 6 are companion cylinders you have to pull the valve cover to see which cylinder you're on. The easiest way is to read the valves. If you watch them as you're turning over the engine you'll see exhaust valve on one closing and then intake open. That's how you know that cylinder is on TDC. You'll have it just about dead on when both the intake and exhaust valves are tight (you can't wiggle the rockers back and forth) and the rockers on 6 should be loose.
Good technique, but now I'm confused. :dunno:. I have a bunch of gas engine experience, and just a bit of diesel experience with my Jetta TDI, but I always thought that TDC for any particular cylinder is the top of the compression stroke when the spark plug (gas) or injector (diesel) caused the combustion. So TDC for say cylinder #1 in the above example is midway between the intake valve closing and the exhaust valve opening, and both rockers should be loose (valves closed) for the compression/combustion cycles. If both rockers are tight with the exhaust valve closing and the intake opening, (due to valve timing overlap) then isn't the engine between the exhaust and intake cycles, and your crankshaft will be 360 degrees (1 full revolution) away from TDC. Aren't the valves closed for any given cylinder for almost 1 full revolution for compression then combustion?

Am I missing something? Or is it just past my bedtime?
 

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There is a timing "window" on the right side of clutch housing and also one on the pump. Remove the timing window on the right side of the clutch housing by removing 2 screws. There you can see the side of the flywheel. There also is a scribed line in the housing opening. You can tun the engine over by engaging a screwdriver in the starter ring gear and using a prying action to turn the flywheel. Watch the side of the flywheel while turning to see the timing marks. There is a mark labeled TDC, 120, and 240. Stop when the TDC is aligned. Then remove the pump timing window by removing two flat head screws on small rectangular plate. In there is a timing mark on the stationary ring and rotating one. If they are aligned or close, then you are on #1 TDC. If not you are on #6. In that case, you will need to rotate flywheel one more revolution to be on#1.
 

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I'm surprised there aren't timing marks on the gears which drive the injection pump. Look for either little ticks or dimples in the gears which should line up at #1 tdc. No matter which way you do this, you are going to be pulling covers off of the engine so don't fight it!

Here is a trick I have used on gas engines and direct-injection diesels. I don't think it would work for an idi diesel. It is crude, but it works surprisingly well. Remove the valve cover and feed a small piece of wire into either the injector or glow plug hole for the #1 cylinder so that it just barely touches the top of the piston. Then, slowly spin the engine over with a wrench until the piston is all the way up and the valves are closed. It helps if you have a minion to turn over the motor while you watch the valves and wire.
 

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Good technique, but now I'm confused. :dunno:. I have a bunch of gas engine experience, and just a bit of diesel experience with my Jetta TDI, but I always thought that TDC for any particular cylinder is the top of the compression stroke when the spark plug (gas) or injector (diesel) caused the combustion. So TDC for say cylinder #1 in the above example is midway between the intake valve closing and the exhaust valve opening, and both rockers should be loose (valves closed) for the compression/combustion cycles. If both rockers are tight with the exhaust valve closing and the intake opening, (due to valve timing overlap) then isn't the engine between the exhaust and intake cycles, and your crankshaft will be 360 degrees (1 full revolution) away from TDC. Aren't the valves closed for any given cylinder for almost 1 full revolution for compression then combustion?

Am I missing something? Or is it just past my bedtime?
Ditto what AllenR stated except when engine is on #1 TDC one should be able to wiggle both rocker arms on #1 cyl. At least that's the way it was way back when I was a JD dealer service manager in the 70's-80's.
My thought too, I just could not word t as well as these guys. You will not want a tight rocker on valves of a cylinder about to be fired.
 

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Diesel Engine: Valve cover does not need to be removed to find TDC on # 1 cylinder.

Remove the timing window on the side of the injection pump.
Rotate the engine at the flywheel timing mark window until the TDC mark is aligned with the groove in the housing.
You're on TBC #1 when the two marks in the pump timing window are also aligned. If not, you're on TDC #6. Rotate the engine 360°.

Auto part Automotive engine part Line art
 

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Diesel Engine: Valve cover does not need to be removed to find TDC on # 1 cylinder.

Remove the timing window on the side of the injection pump.
Rotate the engine at the flywheel timing mark window until the TDC mark is aligned with the groove in the housing.
You're on TBC #1 when the two marks in the pump timing window are also aligned. If not, you're on TDC #6. Rotate the engine 360°.

View attachment 49121
My John Deere 5210 Standyne DB4327-5360 Injector does not have a removeable window. It's leaking, and I cannot find any parts manual for the pump, but I'm trying to remove it to see what I CAN do, but can't figure out the tdc issue.
 
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