Where do you check timing? See picture - PeachParts Mercedes-Benz Forum

dannym · #1 05-26-2005, 08:32 AM

Which point do you check timing at?

I use point A.

I'm having some serious problems here.
I tried to check my chain stretch but my cam has code 11 on it. I can't find any information on this code so I decided to use the cam tower markings instead of the usual 2mm valve lift method. Doing this I got 4 deg stretch.
Now I decided to adjust my injection pump. I used the injection pump holding tool for this. You set the crank to 15 deg ATDC minus chain stretch, so I set the crank at 11 deg ATDC on compression stroke. Put the tool in adjusted the pump. Tool popped in and set the timing. Put everything back together and it runs like crap!
It was bouncing at start up and barely stayed running. lots of smoke too.

I don't know what to do now.
I'm thinking about putting the crank to 15 deg ATDC and setting the pump back to the way it was. Other than that I'm completely at a loss, other than take it to an Indy but I really don't want to do that.

Any input would be greatly appreciated.

Danny

Pete Burton · #2 05-26-2005, 09:00 AM

First, I would put it back where it was and see if it runs better, it should. Second, I'm not sure I understand the theory about "subtracting chain stretch" IIRC, you are saying that the later the cam timing is, the earlier the injection timing should be. Doesn't make sense to me. If valve timing was 10 degrees late, would you make injection timing 10 early? Then they would be 10+10=20 degrees off an ideal position.

IMHO, best way is to 1. Get injection timing 24-25 BTDC. This properly fixes relationship between injection and position of pistons. 2. Get a $20 dial indicator set with probes and base. Check valves based on neutralized #1 intake at 2mm lift. If valves are within 3-4 degrees, leave it alone. Otherwise, correct with offset key and/or new timing chain.

dannym · #3 05-26-2005, 09:29 AM

Hey Peter,
I tried the drip method and it didn't work well for me. I thought the holding tool method woud be more accurate.
Click here for thread on timing tool

Checking chain stretch with 2mm valve lift without the specs for the #11 cam would just be guess work anyway. I checked with a dial indicator but I don't have the specs to work with. I read 12 deg on balancer at 2mm lift now what do I do with that?

What I am just realizing now is the crank is supposed to be set at 15 deg ATDC on compression stroke minus 1/2 chain stretch. Not minus chain stretch. That would put the crank position at 3 deg off where it's supposed to be.
Guess I'll be back out there again tonight. Darn this sucks. I hate working in the carport at night.
I think that's why I make stupid mistakes. I'm trying to get done before it gets dark.
I really need a garage BAD!

Danny

JamesStein · #4 05-26-2005, 10:39 AM

Quote:

Originally Posted by dannym

I think that's why I make stupid mistakes. I'm trying to get done before it gets dark.
I really need a garage BAD!

I know the feeling. Pulled a prechamber with the glowplug still in it last night, trying to beat the sun.

JimmyL · #5 05-26-2005, 11:31 AM

I wish somebody would at some point photo-document the 2mm valve lift timing thing. With the limited way my brain pan works, I have to SEE something, I can't always read about it and visualize. I'm hopeful at a GTG this can be demonstrated, but we have to have one first.
Running like crap and smoke. Hmmm, sounds familiar....

P.E.Haiges · #6 05-26-2005, 11:45 AM

Dannym,

Isn't there a line on the pointer in the middle of the 2 marks in your pik? If you can't find it, maybe you could take the correct timing as the average of the 2 readings. Or maybe U can clean the pointer and fund the mark.

I kinda think you fixed something that "wasn't broken and now you have to fix it until it isn't broken".

P E H

Pete Burton · #7 05-26-2005, 11:47 AM

you should be reading from point "A"

dannym · #8 05-26-2005, 12:10 PM

Quote:

Originally Posted by JimmyL

I wish somebody would at some point photo-document the 2mm valve lift timing thing. With the limited way my brain pan works, I have to SEE something, I can't always read about it and visualize. I'm hopeful at a GTG this can be demonstrated, but we have to have one first.
Running like crap and smoke. Hmmm, sounds familiar....

There are pictures in this link:
http://skinnerbox.steaky.org/Service/W123/w123CD2/Program/Engine/615/05-215.pdf

Quote:

Isn't there a line on the pointer in the middle of the 2 marks in your pik? If you can't find it, maybe you could take the correct timing as the average of the 2 readings. Or maybe U can clean the pointer and fund the mark.

I kinda think you fixed something that "wasn't broken and now you have to fix it until it isn't broken".

P E H

Definitely no mark in the middle. There's no dirt on it at all. I thought point A was right I just wanted to make sure.

Something wasn't right. I was getting 20 mpg. What I wanted to do was check timing, Adjust IP, pull and clean injectors then make/borrow a Prechamber puller and pull them.
Stuck on adjust Ip right now.

Danny

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