Chain stretch... 10 degrees BTDC? - Page 5 - PeachParts Mercedes-Benz Forum

Brian Carlton · #61 08-05-2008, 09:21 PM

Quote:

Originally Posted by Stevo

Be careful not too loose the washer down the hole when removing the sprocket

........yes..........be very careful..........

81Wagon · #62 08-15-2008, 05:54 PM

Okay, I got my 10 degree woodruff key today. I had no trouble installing it, thanks to all your instructions (and many many warnings!). BUT...

The crank still reads 10 degrees BTDC. I went around multiple times to make certain, and sure enough, there has been NO change.

How can the key have done nothing??

It'll only take me a few minutes to reinstall the stock key, so after lunch I'm going to try that and see if it still reads -10 degrees with that one...

81Wagon · #63 08-15-2008, 07:04 PM

Tried the stock key again: 10 degrees BTDC.

Tried the 10 degree offset key installed to the right/clockwise (the way you'd put it in to make up for normal chain stretch): 12 degrees BTDC (should be -19 or so with the key in that position).

This isn't making any sense...

jt20 · #64 08-15-2008, 07:40 PM

where did you get this engine?

you need to closely examine the timing sections in the FSM and figure this out. Someone has messed up the entire timing system while trying to fix it.

A Different Key Is Not Going To Solve This.

http://www.pauldrayton.com/uploadfiles/merc/Service/W123/Index/617Tindex.html

81Wagon · #65 08-15-2008, 07:53 PM

Quote:

Originally Posted by jt20

Someone has messed up the entire timing system while trying to fix it. A Different Key Is Not Going To Solve This.

Clearly. But I don't understand how the key could possibly have zero (or little) effect... Thanks for the link, I'll check it out.

jt20 · #66 08-15-2008, 08:20 PM

Oh, I didnt realize that was the issue.

have you compare the two side by side? Are they both the same offset?

jt20 · #67 08-15-2008, 08:24 PM

remember also that this method is not incredibly accurate. There is strong skewing of results due to human error.

Are you rotating the engine with the glow pugs or injectors removed?

how are you rotating? (specifically)

jt20 · #68 08-15-2008, 08:29 PM

and are you installing the offset in the same manner as the one you removed? Where are you placing the slack provided by the offset key?

Towards the IP timing gear?

or are you pulling away from the IP gear?

which way was the previous one installed?

81Wagon · #69 08-15-2008, 08:37 PM

The one that was there originally is the stock, no-offset key. With that, I was somehow getting 9 to 10 degrees BTDC reading on the crank. With a new chain, that by itself didn't make any sense, but for lack of any other ideas I thought I'd just see if I could correct it with a key.

I got a 5 degree key for the camshaft (which should change 10 degrees at the crank) and installed it, but got almost no change in the measurement at the crank (1-2 degrees at most).

I've been looking at the manual you linked, but I can't find any explanation for how either of these things could occur

. I'm tempted to just leave things as they were and just try to get the IP timed properly to see if that solves the performance issues...

Alastair · #70 08-15-2008, 08:43 PM

Just a thought.....

Which way are you turning the crank when you're lining up the timing-marks....?

81Wagon · #71 08-15-2008, 08:47 PM

Many questions!

Quote:

Originally Posted by jt20

remember also that this method is not incredibly accurate. There is strong skewing of results due to human error.

The results are repeatable over and over again to within about 1 degree; it's really not that hard to line the marks up exactly.

Quote:

Originally Posted by jt20

Are you rotating the engine with the glow pugs or injectors removed? how are you rotating? (specifically)

I didn't remove glow plugs or injectors. I'm rotating in the direction the engine normally turns (clockwise when you're facing it from the front, I guess). I don't ever go in the other direction.

Quote:

Originally Posted by jt20

Where are you placing the slack provided by the offset key? Towards the IP timing gear? ... which way was the previous one installed?

The original one wasn't an offset key, and I (initially) installed the new one so the offset was to the counterclockwise direction. As such the slack went to the chain tensioner side. When I tried it the opposite way later, the slack went towards the IP timing gear. (The IP has been removed, in case that matters.)

Thanks for the help...

jt20 · #72 08-15-2008, 08:59 PM

If the IP has been removed, turning the engine accurately would be greatly facilitaed by removing either the GP's or Injectors. With that much error though, it certainly isnt the problem.

I hate to say it, but have you attempted trial and error? You obviously need more links between your cam and your crank on the IP side. The main issue is that you do not know which side of the IP to add links.

I suggest (since the IP already out) you add a link on this length or chain and make note of it. Since this is a new chain (how do you know this?) you should leave the original key in.

If you cannot establish a reasonable amount of stretch b/w cam and crank on the pulling side your only reasonable option is to time the IP properly disregarding this strange error.

81Wagon · #73 08-15-2008, 09:32 PM

Quote:

Originally Posted by jt20

I hate to say it, but have you attempted trial and error? You obviously need more links between your cam and your crank on the IP side. The main issue is that you do not know which side of the IP to add links.

I suggest (since the IP already out) you add a link on this length or chain and make note of it. Since this is a new chain (how do you know this?) you should leave the original key in.

I just turned the cam sprocket back one tooth by moving the chain forward one link - does this mean I "added a link" between the cam and crank on the IP? (The slack is just going to get pulled out of it, so I don't know how you can "add" anything there.)

The result, as predicted earlier in the thread, is a change of approx 18 degrees, from ~9-10 degrees BTDC to ~8-9 degrees ATDC...

vstech · #74 08-15-2008, 09:51 PM

it really is VERY VERY hard to line up the timing marks.
I think if you got an offset key, you should put it in, leave the tooth offset by 8 - 9° and see where it settles.
the next step is to get a dial indicator and verify the timing with the .2mm swing method.
I bet there are SEVERAL problems here. I bet your gears are worn from running too long with a lot of offset. the new chain was installed one tooth off, and the only thing that's going to fix it is a new IWIS chain, and new cam, and crank gears, and new idler gear... just for our info, are there little Made in japan stamps on your chain or are they smooth links?
you may even need new IP gears.

81Wagon · #75 08-16-2008, 10:29 PM

Okay, having given up on the inexplicable timing issue (I left the cam timing at 8 degrees ATDC since that seemed to be the most reasonable setting I could get), I decided to see what I'd get by just setting the IP timing properly.

I set the crank to 24 degrees BTDC and reinstalled the IP after lining up its gear with the timing mark. After this I had no trouble adjusting it to 1 drip/sec (previously it was just a constant flow no matter where I moved the pump).

The engine started up and idles much better than it used to. The good news is, the knock seems to have gone. The bad news is, once past 1000 RPM I start getting a loud clicking instead, and the performance (or lack thereof) is unchanged - I have a hell of a time just getting to 70 on the freeway.

What could this clicking mean? I can try to get an audio clip if it'll help.

This is very frustrating and I'm pretty much fresh out of ideas

...