PeachParts Mercedes-Benz Forum - Yet another IP timing question

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Yet another IP timing question

I have spent hours reading and I am more confused now.
Few questions...
I have found that the engine needs to be a certain number of degrees BTDS when installing the new IP. The IP I currently have was removed at TDS, and I have just done a valve adjustment on my engine.(1981 300td) looking at the balancer it shows a reading of 10.

SOO..
1) if the engine needs to be at 23 BTDS to install the pump, what should my reading show since it currently says 10, but I know its at TDS on the crankshaft marks?

2) So whats the big deal if its a little off? I have found people that have timed them a bit off on purpose.

3) If I screw this up, do I have to take the IP off again to do it right....I NEVER WANT TO TAKE IT OFF AGAIN..(if I actually get it back on)

You have to put the pump on its mark, in the picture below you can see a teeth missing and a mark. They have to line up. In the picture below they are not exactly lined up.

http://i185.photobucket.com/albums/x...07/300DT11.jpg

Then put the engine at 24º BTDC in the compression stroke of cylinder 1. Install pump somewhere in the middle of the slots (there are marks on the engine and the pump). Drip time the pump.

I totally understand that, but see question 1-3, for where I am currently confused.

...

yes, a NEW or rebuilt IP that is set to the alignment marks needs to be installed at 23°BTDC, but we removed that IP from a perfectly timed engine at TDC on purpose, so if you do not move the timing on the pump, it'll be perfect, or very close when we get it installed.
I explained all this to you in my shop when we removed it!!!
that's why I made it so clear that the cam timing marks had to be dead on perfect! because the IP is already set where it needs to be.

I'll try and answer the questions I think you are asking!

Quote:

Originally Posted by SpringerNC (Post 2965867)

...

SOO..
1) if the engine needs to be at 23 BTDS to install the pump, what should my reading show since it currently says 10, but I know its at TDS on the crankshaft marks?

When you are standing in front of the engine (scratching your head?) the crankshaft should be turned in a clockwise direction. Do not turn it backwards!

So if your pointer is now pointing at 10 => you now need to work out if that is 10 degrees before top dead centre (BTDC) or after top dead centre (ATDC). Look to the left of the number 10 and see if the numbers increase in value. If they do then you will find that zero degrees has already gone past the pointer...

...so that means you've got 10 degrees ATDC.

If, however, the numbers are getting smaller (as you look left along the scale) then you will see that zero degrees is before the pointer...

...so that means you've got 10 degrees BTDC.

This is all because the crank turns in a clockwise direction as you look at it from the front. You need to "look left" to see what is coming next.

The next thing, however, is to work out which TDC you have! The OM617 is a FOUR stroke diesel engine. The crank turns twice for each whole and complete and SINGULAR revolution of the camshaft.

The TDC you want (to put it in a rather inarticulate way) is "the one before it goes bang" that is the one where the intake valve has closed and the next valve to open is the exhaust valve. On the OM617 the first valve is an intake valve and the second valve over cylinder one is an exhaust valve.

(IP timing is set up in accordance with what is going on with cylinder one - as far as you are concerned the other cylinders are to be ignored => cylinder one is at the front of the engine - the first valve is the valve right at the front - the second valve is the one next to it etc)

Quote:

Originally Posted by SpringerNC (Post 2965867)

...

2) So whats the big deal if its a little off? I have found people that have timed them a bit off on purpose.

...

A bit off?

Well define that please!

My advice is not to approach this job in a haphazard manner - try and be exact - precise - perfect!

Quote:

Originally Posted by SpringerNC (Post 2965867)

...

3) If I screw this up, do I have to take the IP off again to do it right....I NEVER WANT TO TAKE IT OFF AGAIN..(if I actually get it back on)

Yes!

Quote:

Originally Posted by vstech (Post 2966178)

This IP mess has me frazzled, not doubting you vstech, and I get it, but I got to the forums been doing as much reading as possible and I find all these horror stories, and the sticker on my car says 24 degrees, then I read to forget all that and take the valve cover back off and make sure the correct valve is closed visually regardless of any number, accuracy seems to be critical for sure and I never want to take this thing off EVER again....

Quote:

Originally Posted by Army (Post 2966237)

I'll try and answer the questions I think you are asking!

When you are standing in front of the engine (scratching your head?) the crankshaft should be turned in a clockwise direction. Do not turn it backwards!

So if your pointer is now pointing at 10 => you now need to work out if that is 10 degrees before top dead centre (BTDC) or after top dead centre (ATDC). Look to the left of the number 10 and see if the numbers increase in value. If they do then you will find that zero degrees has already gone past the pointer...

...so that means you've got 10 degrees ATDC.

If, however, the numbers are getting smaller (as you look left along the scale) then you will see that zero degrees is before the pointer...

...so that means you've got 10 degrees BTDC.

This is all because the crank turns in a clockwise direction as you look at it from the front. You need to "look left" to see what is coming next.

The next thing, however, is to work out which TDC you have! The OM617 is a FOUR stroke diesel engine. The crank turns twice for each whole and complete and SINGULAR revolution of the camshaft.

The TDC you want (to put it in a rather inarticulate way) is "the one before it goes bang" that is the one where the intake valve has closed and the next valve to open is the exhaust valve. On the OM617 the first valve is an intake valve and the second valve over cylinder one is an exhaust valve.

(IP timing is set up in accordance with what is going on with cylinder one - as far as you are concerned the other cylinders are to be ignored => cylinder one is at the front of the engine - the first valve is the valve right at the front - the second valve is the one next to it etc)

A bit off?

Well define that please!

My advice is not to approach this job in a haphazard manner - try and be exact - precise - perfect!

Yes!

Thanks ARMY, just trying to wrap my very visual brain around this stuff..long time wrencher, very new to internals and only 2 weeks in as a desire tinkerer.
I appreciate the help, I think I'm getting it straight in my head now...need to stop reading so much...

Great explanation Amy it will help me figure out how much timing chain stretch I have on my 85 300 SD.

Quote:

Originally Posted by vstech (Post 2966178)

In theory, that is true. In practice, it's next to impossible to achieve.

Quote:

Originally Posted by vstech (Post 2966178)

...

I explained all this to you in my shop when we removed it!!!
that's why I made it so clear that the cam timing marks had to be dead on perfect! because the IP is already set where it needs to be.

Set the crankshaft angle to correspond with the IP timing marks. Otherwise, all frame of reference with respect to the IP is lost if the IP gets moved in the removal/installation process. Then adjust the IP timing by your chosen method.