Top End Teardown

maxwellp · **Posted:** Sat Mar 03, 2012 7:51 pm

msilbernagel wrote:

There's an index 'dot' on the crankshaft pully that the service manual instructs you to place at 12 o'clock, and then rotate CW (right when facing the engine) 90 degrees until the dimple/index is at 3 o'clock. I did this and the pin when into the flex place with no adjustments, several times.

When you've taken the belt off for top-end service as we have, and follow the FSM instructions using the Miller Tool pins as instructed, there is no 180 degrees off; that is what the pins are for.

Mark

X2 That.

Also you can not get the crankshaft out of phase by tuning it 360. Every time you come back to 12 o'clock you are where you just came from. :pepper:

msilbernagel · **Posted:** Sat Mar 03, 2012 8:34 pm

I agree, it's confusing. Let me try a picture to see if we can get on the same page, or have a gizzled friend of Rudolf Diesel chime in.. and while it probably sounds pedantic or lecture like I am only trying to be complete and assume as little as possible in the explanation so that everyone can understand what I'm saying and also pick it apart if I err. Please be patient!

First, it's a four-stroke. Meaning, the crank goes through two complete revolutions for each cycle:

1. Intake: First 180 degrees of crank motion. The piston goes down and sucks in clean air while the intake valves are open, exhaust valves are closed; ignoring overlap. Intake stroke ends at 180 degrees or BTC.
2. Compression: The second 180 degrees of crank travel, where piston goes up and compresses the air - heating it. Ends at TDC, 360 degrees (1/2 way) into the four-stroke cycle.
3. Power: With the piston again at top-dead-center fuel is injected. It is ignited by the hot air, which expands and pushes down the next 180 degrees to BDC and completing the first 1 1/2 turns of the crank (360 + 180, or 540 degrees).
4. Exhaust: The piston is on the up stroke of the last 180 degrees, pushing exhaust out as it approaches the end of the fourth cycle and completing 720 degrees of travel.

So, a 'stroke' is 1/2 turn of the crank where the piston either travels top-to-bottom, or bottom-to-top.

Meanwhile, the CAMs are turning at 1/2 the speed of the crankshaft because their pulleys have twice the teeth of the crank... so for every 180 degrees (1/2 turn) of crank spin there are only 90 degrees (1/4 turn) of CAM spin. In the full 4-cycle, or two revolutions of the crank, the CAM only completes one complete revolution. I think this is the key to understanding why you cannot be out of phase if all the pins are installed. Moving on..

Last tidbits that help understand the mechanical side. If you look at the crank it's like most 4-cylinder engines, where cylinders one and four are UP when cylinders two and three are DOWN. This balances the mass as it rotates.

Also - typical firing order for such a 4-cylinder is 1-3-4-2.

That said, the following table then shows you where all the moving parts are as the engine (crank) goes through the two complete revolutions (720 degrees) of the 4-stroke cycle (click to view on webshots, and then click again to go full screen):

You can see, with the yellow highlight, that there is ONE and ONLY ONE place in every TWO crank (not cam, CRANK) revolutions that BOTH the crank PIN in the flex plate and the CAM PINs all line up at the same time.

In the 180-degree out of phase scenario that I think you are concerned about, the crank pin would go in BUT THE CAM PINS would NOT. Said a different way, the crank pin would line up twice during it's two revolutions but the cam pins would only line up once because it only rotates once during the two complete turns of the crankshaft. During the second crank pin alignment, the cam pin holes would be 180 degrees away from their alignment pin position.

So - everyone - help me here and see if I've missed something?

Thanks - Mark

maxwellp · **Posted:** Sat Mar 03, 2012 9:09 pm

Looks good.
I was just talking about the crankshaft. There was discussion about pulling the timing belt off, then pulling the crank pin and rotating the crank 360 deg. Then put the crank pin back in and put the timing belt back on. I was just saying this will not change anything. :wink:

As far as just the crankshaft, a Compression stroke and an Exhaust stroke are the same thing. Piston goes up.

msilbernagel · **Posted:** Sat Mar 03, 2012 10:02 pm

Sorry - I was responding to turbobill.

maxwellp wrote:

Looks good.
I was just talking about the crankshaft. There was discussion about pulling the timing belt off, then pulling the crank pin and rotating the crank 360 deg. Then put the crank pin back in and put the timing belt back on. I was just saying this will not change anything. :wink:

As far as just the crankshaft, a Compression stroke and an Exhaust stroke are the same thing. Piston goes up.

turbobill · **Posted:** Sat Mar 03, 2012 11:00 pm

Thanks, msilbernagel, I think I can better explain my supposition using your chart. My supposition is that the crank was at 450 ATDC - 1 1/4 turns Crank Pos when the pin was inserted into the flywheel and the cams were pinned while off the engine so they were set to 45 ATDC 1/8 rather than at 225 ATDC CAM Pos where they belonged. Harlan had removed the cylinder head cover without pinning the cams and he worked on one of the cam lobes because it was scored a bit by the edge of one of the broken rockers. He had the cams off the engine when he picked up my pins to use for timing the engine.

When the engine was put back together then the crank was at 450 ATDC - 1 1/4 turns Crank Pos and the cams at 45 ATDC 1/8 turn Cam Pos and were out of time. In this position there is no valve interference so the engine turns over just fine but will not start.

These numbers are not on the chart provided because the second time the flexplate hole aligns is not part of the chart stats so I just added the needed amounts to the 1 turn crank position. I think the numbers are correct.

msilbernagel · **Posted:** Sat Mar 03, 2012 11:45 pm

Ok (turbobill), I think we're getting closer.

Yes... but.. If you rotate the crank then it, the pistons, and the flexplate and its hole are exactly as they were one turn (360 deg) earlier.

What takes the crank more than 360 degrees into the full four stroke / 720 degree cycle is where it is relative to the cams.

If you pin the crank, it's pinned at 90 degrees ATDC - if and only if (IFF) - the cams are also pinned. Just the act of pinning both is *by definition* setting the engine to 90-degrees into the 720 degree cycle.

The position not on the chart that you refer to is when the crank has come full circle (1 turn / 360 degrees + 90 to the pin) and the cams have advanced 1/2 turn (180 degrees) + 45 degrees - at that point you cannot get the pins in because the cam holes are on the opposite side of the camshafts from the holes in the engine cover.

If I were to add the line to the spreadsheet where you are speaking of (crank at 450), the crank alignment hole in the flexplate and the hole in the block would be 0 degress apart - ALIGNED - but the CAM pin holes would be 135+45 (180) degrees from the engine cover holes - NOT ALIGNED.

Don't know if that helps... but I remain convinced you cannot be 180-degrees out of time if all the pins are correctly installed.

As further evidence I offer this: the factory service manual mentions *nothing* about this as a possibility; what are the odds?

Mark

mtgstuber · **Joined:** Tue Sep 13, 2011 4:15 pm **Posts:** 66

Let me start by saying, I completely agree with Mark's analysis. And I really hope he's right, because my top end is in pieces right now and I really hope it works when I put it all back together. But as to this last point . . .

Quote:

As further evidence I offer this: the factory service manual mentions *nothing* about this as a possibility; what are the odds?

You're kidding right?

turbobill · **Posted:** Sun Mar 04, 2012 1:16 am

OK msilbernagel. I am convinced you are right. The bottom end of the engine doesn't know anything. With the fuel pump and cams properly timed the engine should work just fine. Harlan has another problem keeping his engine from starting.

msilbernagel · **Posted:** Sun Mar 04, 2012 1:53 am

mtgstuber wrote:

Let me start by saying, I completely agree with Mark's analysis. And I really hope he's right, because my top end is in pieces right now and I really hope it works when I put it all back together. But as to this last point . . .

Quote:

As further evidence I offer this: the factory service manual mentions *nothing* about this as a possibility; what are the odds?

You're kidding right?

Tongue was firmly embedded... :ROTFL:

Still - it is a possibly likely to be documented if possible.

galatron · **Posted:** Mon Mar 05, 2012 1:42 pm

Oh my gosh, I leave for one weekend, and look what you guys did to my post! :CAMPING:

So here's what I've figured, just by messing about... and I do mess about.
You can set the crankshaft 90 ADTC lock it, and then you can turn the cams about anywhich direction you want, 360, 940, whatever. either one, exhaust, intake. (which is actually a misnomer as both cams do each other's job, intake and exhaust cams ride on both cams - they alternate.) SO I can rotate both cams and they feel the same resistance, the pins line up on a 360 rotation. - I still don't have the official pins yet - so, Turbobill, yes if you want to stop by this evening I'd be very happy to make another attempt at using your tools.
IF you lock the cams in place and you try to turn that crank it will not rotate much farther than past 90ADTC - it WILL contact the valves and you can back out. YOU CAN feel it if you are not using too much pressure, probably enough to depress the flesh on your arm.

galatron · **Posted:** Mon Mar 05, 2012 2:48 pm

hmm, perhaps this is why we have to have the fuel system timed with the engine. I can't see any reason why the cams and the crank would matter in regards to the pins, cold timed, the pins are the rulers.
Now in regards to firing, the fuel pump time and the electronics would make a difference.
There's the cam sensor, certainly the injectors are not inputting fuel into all four cylinders each time we reach TDC.
How does the cam sensor know which piston is in the compression mode?
Is there a crankshaft position sensor?
Does anyone know what the outputs are of the cam or crankshaft position sensor are? eg, on-off, or datastream?
Thanks for all the help and suggestions.

maxwellp · **Posted:** Mon Mar 05, 2012 8:47 pm

Got the FSM out.

Is there a crankshaft position sensor?
Yes

maxwellp · **Posted:** Mon Mar 05, 2012 9:44 pm

"certainly the injectors are not inputting fuel into all four cylinders each time we reach TDC."

No fuel is only injected in to the cylinder that is going to fire. This is all done by the ECM telling each injector to spray at correct time. The ECM uses the sensors to tell it where things in the engine are. That is why it must be put together correctly, the ECM only know where things should be with the inputs. If the engine is assembled wrong if still trys to use the inputs as if they are correct. Also if it does not get input from the cranshaft and cam sensors it will not run. Hope this made some sence. :pepper:

maxwellp · **Posted:** Mon Mar 05, 2012 9:55 pm

"How does the cam sensor know which piston is in the compression mode?"

The cam sensor would not know.
The ECM will use the cam sensor and the crank sensor inputs to determine where the piston are in the cycle. This is all in the program code of the ECM. That is also why if the ECM can not "see" these sensors and get there input as to what is happening the engine will not run. Make sense?
:pepper:

galatron · **Posted:** Mon Mar 05, 2012 10:38 pm

OK so if this is the case I have a one in four chance of reassembling correctly. How can we be sure that I have reassembled electronically correct? As I am now more than positive that it is mechanically correct.
I spoke with Turbobill earlier and he said that he also was sure that we had the thing timed properly. I agree. I suggested that since the "exhaust " cam has the sensor on it. Perhaps it should be revolved 360 at a time until the engine started (separately from the rest of the engine in an attempt to get the engine in time electrically)

maxwellp · **Posted:** Tue Mar 06, 2012 12:39 am

galatron wrote:

OK so if this is the case I have a 1 in four chance of reassembling correctly. How can we be sure that I have reassembled electronically correct? As I am now more than positive that it is mechanically correct.
I spoke with Turbo bill earlier and he said that he also was sure that we had the thing timed properly. I agree. I suggested that since the "exhaust " can has the sensor on it. Many it should be revolved 360 at a time until the engine started (separately from the rest of the engine in an attempt yo get the engine in time electrically)

If all three pins are in at the same time, it is assembled correctly. I don't understand what you mean by "reassembled electronically correct". All the sensors ect..... plugged back in/installed. You would not need to just spin the exhaust cam, there is a base timing to start the engine in the ECM programing code. If all is good in the mechanical department you have an electronic problem.

Have you hooked up the ECM to a scanner? Does it power up? Fuses all good? Is it all put back together? Grounds alll hooked up? Just thinking of things I have seen.

galatron · **Posted:** Tue Mar 06, 2012 2:06 am

Honestly, I don't know. I was thinking that how does the electronic side of the engine know which cylinder is in compression mode.

geordi · **Posted:** Tue Mar 06, 2012 2:46 am

Crankshaft position sensor, which should be on the passenger side, at the back by the flex plate, near the top. (At least I'm reasonably certain that's what I saw back there on mine.)

The engine makes one revolution, the computer now knows exactly where it is if it forgot.

maxwellp · **Posted:** Tue Mar 06, 2012 9:40 am

Here is the crankshaft Sensor. Number 3 in the top picture.

maxwellp · **Posted:** Tue Mar 06, 2012 9:53 am

"I was thinking that how does the electronic side of the engine know which cylinder is in compression mode?"

Number 11 in this picture is the Exciter ring on the crankshaft. This is what the crankshaft sensor is reading. It looks like starter ring gear, but there is a "keyed" tooth so the ECM knows what TDC is. Then it counts the teeth as it spins. All this info is played out in the ECM code. That is how the ECM knows where things are and what to do. So if the ECM does not get this info it can not start the engine because it does not know what is happening.

As far as the ECM, it knows where engine parts are at every degree, it knows what degree by counting teeth on the Exciter ring.

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