Chain Strech/Injector Timing Questions - PeachParts Mercedes-Benz Forum

jkubica · #1 05-10-2010, 10:24 AM

Greetings All

I've seen a number of threads here dealing with timing chain strech and also injector pump timing.

My questions:
How often and at what millage generally do these problem develop with the 617 engine - & what signs would point toward needing to check them?

Is improper pump timing the result of excessive chain strech - or something else?

What effect would these problems have on fuel economy? Would they result in excessive soot formation?

I want to do whatever I need to for keeping my engine running correctly - but don't want to do a bunch of unnecessary work in the process.

All information appreciated!

Joseph

Diesel911 · #2 05-10-2010, 11:17 AM

Most of the questions you have have a variable answer because it would depend on how the previous owner/s maintained there vehicles.
The Timing Chain would not show symptoms until it is really bad.
The Injectors might cause poor Fuel economey and hard starting. (Part of the Injectors job is to atomize the Fuel into small particles so it burns well.)

I would pull the Valve cover off; rotate the Engine in the direction of rotation and line up the Camshaft Gear timing marks with the marks on the Camshaft Bearing tower; line them up perfectly (the Red Arrow in the left side of the first pic points to the timing marks aligned).
After that look down at your Crank Dampner at the degree marks and see what the pointer shows. When set at the Factory it was set at Zero degrees (Top Dead Center).
If you look at the right side of the first pic you see a Blue Arrow pointing to zero degrees. If you look at the Engine pointer you see I am showing about 2 degrees of late Camshaft Timing (due to chain stretch and Timing Gear Wear). If my Fuel Injection Pump had never been re-timed it would also have late timing as it is driven by the chain.
If you get something like 3- 4 degrees I would do the more concise test; the 2mm method covered in other threads.

On the Injectors the stock Spray Nozzles have some holed drilled into the tip of the Pintel (see 2np pic).

On my Engine when I pulled the Injectors it looked like they had never been out of the Enigne and checked for 198,000 miles.
This was at least 98,000 miles too late. I found that all of the holes in the Injector Pintel were competely plugged solid with Carbon and the pop/opening pressures were low.
Also most of the Injectors I have pulled at the Junk Yard also had the drilled holes plugged.
I think unless a regular Purge (or the Injectors are pulled, taken apart and cleaned) is done on Injectors with this type of Spray Nozzle they are eventually going to plug up.

They 3 things on the Engine that will most effect your Fuel economey are a Valve Adjustment,Injectors up to specs and the Engine Compression.
After that it would be the IP timing.
(The Fuel Injection Pump can also have some internal wear that alters the timing but it is not that much as long as the Oil has been changed on a regular basis.)

barry123400 · #3 05-10-2010, 01:59 PM

Timing chain condition is dependant on the frequency of oil changes in the past. It wears the most of any engine component with infrequent oil changes.

Also why a good method of checking for stretch should also be used is it may have already had a replacement chain installed sometime before you aquired the car..

jkubica · #4 05-10-2010, 02:29 PM

Quote:

Originally Posted by Diesel911

Most of the questions you have have a variable answer because it would depend on how the previous owner/s maintained there vehicles.
The Timing Chain would not show symptoms until it is really bad.
The Injectors might cause poor Fuel economey and hard starting. (Part of the Injectors job is to atomize the Fuel into small particles so it burns well.)

I would pull the Valve cover off; rotate the Engine in the direction of rotation and line up the Camshaft Gear timing marks with the marks on the Camshaft Bearing tower; line them up perfectly (the Red Arrow in the left side of the first pic points to the timing marks aligned).
After that look down at your Crank Dampner at the degree marks and see what the pointer shows. When set at the Factory it was set at Zero degrees (Top Dead Center).
If you look at the right side of the first pic you see a Blue Arrow pointing to zero degrees. If you look at the Engine pointer you see I am showing about 2 degrees of late Camshaft Timing (due to chain stretch and Timing Gear Wear). If my Fuel Injection Pump had never been re-timed it would also have late timing as it is driven by the chain.
If you get something like 3- 4 degrees I would do the more concise test; the 2mm method covered in other threads.

On the Injectors the stock Spray Nozzles have some holed drilled into the tip of the Pintel (see 2np pic).

On my Engine when I pulled the Injectors it looked like they had never been out of the Enigne and checked for 198,000 miles.
This was at least 98,000 miles too late. I found that all of the holes in the Injector Pintel were competely plugged solid with Carbon and the pop/opening pressures were low.
Also most of the Injectors I have pulled at the Junk Yard also had the drilled holes plugged.
I think unless a regular Purge (or the Injectors are pulled, taken apart and cleaned) is done on Injectors with this type of Spray Nozzle they are eventually going to plug up.

They 3 things on the Engine that will most effect your Fuel economey are a Valve Adjustment,Injectors up to specs and the Engine Compression.
After that it would be the IP timing.
(The Fuel Injection Pump can also have some internal wear that alters the timing but it is not that much as long as the Oil has been changed on a regular basis.)

Hi Diesel911
Thank you for all the information.

I don't know for certain that I have a problem with fuel consumption since my odometer isn't working and I can't measure it accurately. I seem to have plenty of power and no black smoke.

I've set the valves and rebuilt the injectors using Monarch nozzles. They are all popping at 2000psi (138bar). When I pulled the injectors, I did a cold compression check (50 degrees outside) and got 350 - 360 psi all across. I also soaked the cylinder with Marvel Mystery Oil while for a couple weeks while I ordered the nozzles and worked on the injectors.

After installing the injectors I let the engine idle for about 30 minutes and then had to pull one of the injectors and redo it because it was leaking. I was surprised to find the nozzle end was already heavily coated with soot/carbon. That made me wonder if I had poor combustion due to IP timing being off. Or was the carbon buildup just from the long idle?

I'll follow your advice about pulling the valve cover and checking the timing marks as my next step.

Regards, Joseph

Diesel911 · #5 05-11-2010, 02:31 AM

[QUOTE=barry123400;2464367]Timing chain condition is dependant on the frequency of oil changes in the past. It wears the most of any engine component with infrequent oil changes.

Also why a good method of checking for stretch should also be used is it may have already had a replacement chain installed sometime before you aquired the car..[/QUOTE]

Yes, this is what I wonder about on my Timing Chain. 2 degrees late at 198,000 miles seems to good to be the original Chain.

Or the other possible is someone has installed an Offset Woodruff Key.
I have not taken the time to check and see if one was installed.

vstech · #6 05-11-2010, 09:58 AM

actually, the pic you have showing the timing marks, are not lined up exactly.
your cam is slightly advanced. to get a good view, you want to be sure the mark exactly aligns with the arrow on the tower. perfectly centered between the two marks!

your pic shows the cam mark just past center, and the timing mark on the balancer is double this amount away from 0, so if the marks were perfect I bet that mark on the balancer would be perfect.

Diesel911 · #7 05-11-2010, 02:23 PM

Quote:

Originally Posted by vstech

actually, the pic you have showing the timing marks, are not lined up exactly.
your cam is slightly advanced. to get a good view, you want to be sure the mark exactly aligns with the arrow on the tower. perfectly centered between the two marks!

The Blue Arrow in the upper big pic is pointed at Zero/Top Dead Center. the pointer on the Enigine is pointing to a spot between Zero/TDC and 5 degrees after Top Dead Center.

your pic shows the cam mark just past center, and the timing mark on the balancer is double this amount away from 0, so if the marks were perfect I bet that mark on the balancer would be perfect.

It looks perfectly lined up to me. Perhaps some other Members will chime in and give their opinion.
Remember this is this the same method that is used when the Enigne is built new and also when it is rebuilt.

Wayfarer · #8 05-11-2010, 04:27 PM

[QUOTE=Diesel911;2464797]

Quote:

Originally Posted by barry123400

Timing chain condition is dependant on the frequency of oil changes in the past. It wears the most of any engine component with infrequent oil changes.

Also why a good method of checking for stretch should also be used is it may have already had a replacement chain installed sometime before you aquired the car..

Yes, this is what I wonder about on my Timing Chain. 2 degrees late at 198,000 miles seems to good to be the original Chain.

Is there any way to tell if a chain is factory new or has been replaced? I would think that it would have some kind of a special link if it was replaced, but not sure how to tell even if it had one.

barry123400 · #9 05-11-2010, 05:42 PM

No special link. The only clue might be a poor installation of the link that ties the two ends together. It is not a unviersal clip one on most these cars. They apparently had failure issues so that type fell out of favour.

It instead looks like any other link in the chain and the ends are peened over either by hand tools or a special tool. Accurate chain stretch measurements are the way to go in my opinion. Remember it could have been replaced so many miles ago that it too is worn quite a lot. Hard to depend on those pesky odometers on these cars.

Diesel911 · #10 05-11-2010, 05:48 PM

The obvious way to know if the Chain has been replaced is if it does not have an IWIS Timing Chain. On the Factory and the replacement Chains the Links are supposed to be peened over.
I do not know if the add on link that you would need to peen on a new chain can be spotted or not. The instuctions for the use of the Crimping tool are to crimp that Add On Link until it looks like the others. So if the add on like looks like the rest of the Chain it would be hard to detect.

If you Chain has a removable Link on it it is a replaced chain.

After that it is a guess. If you have 300,000 miles on the Engine with an IWIS Timing Chain and only 1 degree of Timing Chain Stretch (and no offset Woodruff Key installed) I would suspect that that Chain was a replacement.

(Opinion) Replaced or not if your Chain Stretch measures OK using the 2mm method and no one has installed an OffSet Woodruff Key to compensate for a Stretched Chain it does not matter if it is replaced or not as long as it is an IWIS Chain.

If a the Chain was replaced the other concern becomes if the Timing Chain Tesioner Rail/s were replaced and the condition of the Timing Gears themselves.
From what I have read the consensus seems to be that a new Timing Chain should at least have a new (the large one) Timing Chain Tensioner Rail.

bluetypewriter · #11 05-11-2010, 06:37 PM

Not to threadjack, but the inside of my valve cover shows some chain wear. Is this something I need to worry about?

The car (1982 300TD) has 225,000 on it and I only have partial maintenance history.

winmutt · #12 05-11-2010, 07:14 PM

Wow. Correct me if I am wrong guys but you may need a new tensioner much sooner than later.

bluetypewriter · #13 05-11-2010, 07:59 PM

Quote:

Originally Posted by winmutt

Wow. Correct me if I am wrong guys but you may need a new tensioner much sooner than later.

That's what I was thinking......

vstech · #14 05-11-2010, 10:05 PM

um, yeah... your chain is whipping up a storm! either that, or it was at one point, and has been repaired.

bluetypewriter · #15 05-11-2010, 11:29 PM

Quote:

Originally Posted by vstech

um, yeah... your chain is whipping up a storm! either that, or it was at one point, and has been repaired.

Considering the lack of other repairs I'll get right on fixing this too. Thanks