timing chain stretch /i.p.timing on 240d and a noise question - PeachParts Mercedes-Benz Forum

fochs · #1 11-21-2011, 02:00 AM

I have recently checked chain stretch on my 83 240d. Using the 2mm method, the stretch appears to be 9-10 degrees. In theory, how much and in which direction would injector pump timing need to be altered, if at all, to compensate for this?
I do not know if the woodruff key at the cam has been changed. Setting the pump timing has been problematic so far. I made a drip tube out of an old line and plan on trying to do the set tomorrow. The bubble method produced a result of 24 degrees, but it seemed the timing was far advanced. There was reduced power and a load of gray/black smoke. The pump at this result was at the limit closest to the

engine block. Is there a common range of degrees for the pump timing from lock to lock? If so, what degree range?
After the bubble timing episode, I backed off the pump about an inch away from the block and it runs better, if not good. The car has a noise like a gasser pinging when it is under load. It doesn't happen at idle or at cruising. I wonder if this could be due to the unknown timing, or is it indicative of timing chain noise?
Any help with any of these questions would be much appreciated, thanks.

leathermang · #2 11-21-2011, 10:41 AM

The bubble method is junk because it is too subjective.. the drip method is based on the repeatability and consistency of the amount of liquid in a DROP.....
Use the FSM drip method and let us know how that goes...

fochs · #3 11-21-2011, 12:54 PM

Is there a certain number I should shoot for given the amt. of chain stretch I have? Have to go with what I have, replaced injectors this week and new front brakes complete- out of funds, thanksgiving etc.
I understand that the chain stretch accounts for half the amount of degrees in pump timing. If that is accurate? which way? retard or advance?

leathermang · #4 11-21-2011, 01:19 PM

Have you read the chain elongation thread in my signature ?

Stretch · #5 11-21-2011, 01:39 PM

Quote:

Originally Posted by leathermang

Have you read the chain elongation thread in my signature ?

Same question has been asked here Greg!

chain stretch and injector pump timing 240d - Benzworld.org - Mercedes-Benz Discussion Forum

@fochs - if you think there is a chance you've got an offset key already fitted and you think you've got 9-10 degrees of stretch as well... Well I've posted my feelings on the other forum!

First thing I'd do is check for an existing offset key.

leathermang · #6 11-21-2011, 01:53 PM

Fochs, You did a bike chain when you were young ..... and messed that up....
Perhaps we can provide you with better instructions than whomever you were dealing with at that time.....
But I am with Army about replacing the chain....

Stretch · #7 11-21-2011, 02:59 PM

Camshaft timing is one thing - an elongated chain will change the time at which the valves will open and close with respect to the position of the piston in the cylinder compared with the designed times.

The begin of delivery, however, should be adjusted as specified in the FSM at 24 degrees BTDC. You have to get the fuel into the cylinder at the right time with respect to the position of the piston - If you try to get the fuel into the cylinder earlier the piston won't be in the right place for the combustion to be of any use.

Although the timing of the valves and the IP should work together perfectly - you may as well consider them to be totally separate from each other. You time the fuel to arrive when it should and just hope those bloody valves are doing what they should!

If you look in the FSM chapter 05-215 you can see the positions at which the valves should open and close depending on your cam type.

For example the exhaust valve on a OM617 turbo cam codes 00 and 08 should close at 19 degrees before TDC on a new chain and after about 20,000km it will close at 17 degrees BTDC. According to this thread (Injection Pump Timing and Crank Pulley Question) the pressure is built up in the injector lines enough for the injector to "squirt" between 14 degrees BTDC and 10 degrees BTDC.

The longer you leave your timing chain in an elongated state the chances are greater that the piston gets closer and closer to that exhaust valve...

leathermang · #8 11-21-2011, 05:34 PM

Quote:

Originally Posted by The Gears

jfgkfgkghkghkghjgh

TEST ?

Orv · #9 11-21-2011, 06:22 PM

I think that's a textual representation of the sound of timing chain rattle.

leathermang · #10 11-21-2011, 06:38 PM

Quote:

Originally Posted by Orv

I think that's a textual representation of the sound of timing chain rattle.

LOL, my tongue would not do that so I did not recognize it....

fochs · #11 11-21-2011, 07:27 PM

Hi and thanks for the responses. I attempted the drip tube method of ip timing. Using a cut length of old injector line, I wired the throttle open, pulled the vac line from the cutoff valve, pulled the spring and plunger from the #1 valve and refitted the barrel leaving the copper washer and pressure valve carrier in place then fitted the drip tube. I bled the fuel filter at the bolt and then pumped the hand pump, fuel squirted from the drip tube. I did not get any fuel on engine rotation, I rotated it several many times by the crank bolt clockwise. Did I miss a step here?
One thing- the fuel that squirted from the drip tube seemed foamed. There was not really air in the filter bleed and none in the prefilter. I have replaced all of the engine compartment fuel hoses and return lines and can see no leaks, also none from the hand pump itself, which is of the new style. - oof!

@ leathermang: can the woodruff key investigation be accomplished without removing the camshaft gear? I recall reading that you said it's possible?

@Orv: Ha!, would that happen all the time? or just on acceleration?

Orv · #12 11-21-2011, 07:46 PM

All the time, but on diesels it's hard to distinguish from general clatter.

leathermang · #13 11-21-2011, 09:21 PM

If you search the archives on the fuel supply when doing the drip.... I think some form of container mounted above the engine is the usual method... not trying to get it from the fuel tank...pressurizing by hand pump does not give you reliable steady source for getting to the one drop per second...
I think you can take the nut off the end of the cam and see under it if there is an offset woodruff key... You will need to stabilize the cam by using something stuck into one of the lower sprockets for the loosening and retightening...
Does someone have a reference url to that online FSM ? my signature is full...

Stretch · #14 11-22-2011, 03:22 AM

Quote:

Originally Posted by leathermang

...
Does someone have a reference url to that online FSM ? my signature is full...

You'll find it plastered all over BW - but we're good here right? WE don't publish such things right?

By the way I think you probably are going to be able to see the offset key with just the bolt and washer removed.

Give it a go!

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