Timing chain, replace it at 5* stretch now?
 

Or not? How much stretch is acceptable and if you had the valve cover off on your 1983 300 TDT and a new chain ready to go, would you replace it now or is 5 degrees of stretch no real big deal?

I would and eliminate worry.

How are you measuring it?

That's kinda where I've been leaning! I had the head at a machine shop less than 1000 miles ago and didn't bother to replace the chain then because it looked OK to just drive carefully around town close to home to let everything "settle in."

I'm looking at the timing mark on the Camshaft and lining it up with the matchmark on the cam tower while rotating the engine in the normal direction of rotation by turning it at the crank pully. When the Camshaft mark lines up at the cam tower, the harmonic balancer marks are 5* degress late, maybe a slight bit less.

I'd worry more about the guides, rails & tensioner than I would about the chain.

I did replace the tensioner spring and the slipper foot when I had the head off. The upper guide rails have been replaced as well.

Have you got an offset key in the cam sprocket or the "normal" one. I have a 2.5 degree offset key here which would fix your problem if you want it...

5 degrees is not bad, any more and it becomes questionable. The general rule of thumb is replace the chain every 100,000 miles. I know there will be some that will disagree. It's not hard to do, and with the right crimping tool, can be done in a couple of hours. The last one I did was on the 300D, it had several degrees of stretch, a new chain made a world of difference. The worst one I saw had 12 degrees of stretch, surprised it even ran.

There are some users who will rent the correct crimping tool for a small fee and deposit. Check the tool rental forum. Others have used vise grips, it's a real pain in the ass to do, but can be done.

If you do decide to replace the chain, use a press on master link. Although it makes the job easier, I have not seen an "easy clip" link in years, they were discontinued from MB in the late '90's.

First this not an indication of stretch, this is cam timing. There is like a 4* or more error margin the way you have measured it. Measure it with 2mm lift method. There is no need to replace the chain, bad crimps (common enough) lead to short lifespans. They make offset keys for this purpose and there is no need to crack the chain. There is no specified replacement interval in the FSM, I think they expect the chain to last all the way to the last offset key. Not that I would go that far but I believe 6* is the first offset, you are in spec but if you have the time its probably worth it.

timing chain
 

Roll a new chain in, it,s that simple.

Why risk a bad crimp with a known good chain? Why spend hundreds of dollars when it should only cost a few?

That is interseting as my timing chain shows 2 degrees of stretch (via the Cam Bearing Tower and alignment marks) with just over 200,000 on the odometer.
I do not know if the chain was previously replaced or there is an offset key installed (never worked up enough intrest to check the key yet).

This is a factually incorrect statement.

The reading you got with the Camshaft Bearing Tower alignment method is a good indication you should check further and use the 2mm method to do so. This would also give you the spec you need to pick an offset key; if you want to use on.

To answer the question I think I would replace the Chain if it goes up to 6 degrees stretch as measured by the 2mm method.
If not replacing the Chain I would insert an offset key to return the Camshaft Timing to normal and re-time the IP.

I wonder...
 

I've often wondered about my car, which has 128k on it, or so says the odometer. What if a prior owner disconnected the cable for 100k? I would never know. I guess the only thing I could do to sort of check, would be to do a CarFax report. Might help me locate anything suspicious, like 159k service, then the next one is at 89k, you know what I mean?

But the long and short of it is, if it has more miles on it than the odometer says, then I'm missing doing needed maintenence. :eek: The timing chain is supposed to be checked at 200k, I think.

Well, I replaced the timing chain and now it won't start.:mad: I do have the timing marks on the cam lined up and the marks on the crank at zero. Then turned the engine over by hand a few times to make sure it was all ok. Must be building good compression because it was harder with a new timing chain. The old one was stretched by more than 10*!:eek:

Funny thing though, it didn't feel very powerful before, rather sluggish in fact compared to my 300D and the fuel Injection Pump doesn't give me a shower in fuel like my 300D does. I would think even if the IP was timed wrong, it would still spray large amounts of fuel with the lines cracked. Could my IP have puked?:confused:

The marks have to be lined up at TDC on the compression stroke. Take out the #1 Glow Plug and crank the Engine by hand and see if you feel compression as you are approaching the Camshaft alignment marks. When it is aligned take a look at the Damper degree marks and see if it is at "0".

It is unlikely that the IP puked; but very likely that it needs to be timed again; after you are sure the Camshaft timing is OK.

Nobody listens to me.

I do ;)

A common problem around here.........and it's not just you.

Can you explain a little more how the cam tower mark method is not an indication of chain stretch? I mean, it SEEMS like it would be a quick way to check, albeit not very accurate, but I'm still pretty new to engine timing and whatnot.

The cam tower marks are used when first installing the cam to the engine, nothing more. It was never intended to be used to measure chain stretch.
Mercedes gave a precise way to measure it. That way is 2mm valve lift on intake #1.

That said. If you had 10* of stretch and it was running fine then your IP was timed to 10* stretch. With a new chain you now have to retime your IP.

Danny

Wait a minute!!
 

That makes no sense. This is what you should see:

For engines 617.950 (1980 and after), 617.951, 617.952; Camshaft code 05, specs are:
With new chain, 9 degrees ATDC.
With used chain (from approx. 20,000 Km), 11 degrees ATDC.

You really need to stop using the cam tower marks.

FYI
Mercedes Benz makes 4 woodruff keys for the correction of cam timing:

Part # 621 991 04 67, Offset 0.7 mm, For correction of about 4 degrees.
Part # 621 991 02 67, Offset 0.9 mm, For correction of about 6.5 degrees.
Part # 621 991 01 67, Offset 1.1 mm, For correction of about 8 degrees.
Part # 621 991 00 67, Offset 1.3 mm, For correction of about 10 degrees.


Danny

Because I own a chain crimper and popper, so I can put it on with the correct tools. I've also seen what happens to these engines when a timing chain breaks and it usually isn't when idling or first cranking it up, it's on the highway where you cannot stop and severe engine damage is a result!

Its a total waste of time to replace the chain if you don't replace the guides and rails as well.

Nope. The timing changed because of elongation of the chain. Replacing the chain will eliminate that slack and return the IP and cam to their original time.

That's what I thought! I know now where my problem is. While installing the new chain, I lost my grip on it fore a half second and the short whirr I heard, if you can call it that, was the IP turning against spring pressure and now it is running about 1/4 of one full rotation too late.:( Unless you have another idea, it would appear that removal of the IP and putting it back in the correct position and then timing it properly is my next step!:D

I bought one of my wagons with a severely damaged engine. At 141K miles, the timing chain broke while Monty was going down I-17 into phoenix when the chain broke. It dropped into the chain area and wound up in the oil pump drive chain, breaking that into pieces and ripping the oil pump sprocket off the oil pump in the process and breaking the oil pump shaft. Since the engine was still turning, the camshaft broke into 3 pieces, the camshaft sprocket was in too many pieces to count, and the camshaft itself was in 3 pieces along with the cam towers!:eek: Valves were bent and had to be replaced. I have this engine on my workbench right now because I bought this car with a damaged motor, so I'm a little nervous about replacing them thar darned chains! I'm rebuilding this engine since it looks like all the damaged parts are ones than can be replaced. Nothing more expensive than a cheap Mercedes!

One thing I do not understand though, according to my FSM, if the chain was installed properly then you should be able to rotate the motor by hand and the Camshaft marks will line up with the notch on the cam tower while the crankshaft mark is at 0. If this original setting/ examination was 5* late on the camshaft marks, wouldn't you think the timing chain was getting worn out? When I compared it to the new one side by side, the old one was more than an inch longer!:eek: It was also quite a bit more flexible in side to side movement.

Did ya'll say something? :rolleyes:

Don't feel like the Lone Ranger...
Maybe we should start a Rodney Dangerfield memorial " I get no respect" club.

Anywho, hang in here to help fuel discussions for those of us who just might accidentally absorb a tidbit or two...

Motor still on

Still no start after removing and setting the IP.:mad: I still feel as if something is wrong with this IP. It just didn't have the performance you should expect for a 5 cylinder turbodiesel! My 300D will peel rubber if you punch it on slick pavement from a standing start. This car, one of my wagons, had no get up and go period. I could get passed by a 240 on flat ground. It only ran well when cold and once fully warmed up, idle was rough, engine would rock back and forth and it felt like an ignition miss!

This is not the first time I've done this. When I've got the whole thing apart, set the crank at 0, set the cam lined up with the matchmark on the front cam tower and the IP marks lined up together which you can only see with the IP out and it fired right up! This time nothing. And if you stop using the lift pump to send fuel up to the engine, it all drains back out of the IP back to the tank. Through the injector lines and the drip method isn't working.

that might indicate your lift pump is failing. I am not certain. Try a few searches for lift pump repair and check the DIY articles / links

It's possible the lift pump has failed or about to. It was recently replaced though with the updated design you don't have to unscrew to operate it by hand. I have a spare IP known to be good. I'm working on a friends house today helping him repipe. Tomorrow I should be able to install the known good one and see what happens. Now that I think of it, the old one has a peculiar quirk, a noticeable variation in the idle of about 350 RPM. Kinda odd, up, then down, then back up and down and kinda gutless too.

Here's my take on what you've got:

The IP was fine before you replaced the chain. Therefore, there is no possible scenario that causes the IP to fail during the chain exchange. Sure, it might not be putting out fuel to spec, but it cannot prevent a start.

Furthermore, the lift pump cannot fail due to a chain exchange. If the pump was working before the chain exchange, it's certainly working now.

So, the question begs whether you've got fuel at the injectors, or not. Crack two injector lines and crank the engine for 15 seconds with full pedal. Fuel should come out of the two open lines and wet down the head in the area of the injectors. It won't be much.......but it won't be zero.

If you have fuel, the IP is fine. Your problem is then caused by the lack of proper IP timing. The story that you provided here on the forum is not what you did on the vehicle. We really can't help you further with it until you start at the beginning and find the error of your ways.

I agree that my initial problem was caused by the lack of proper IP timing, but I already tried to crack the injector lines and crank it to see if fuel was coming out and it does deliver some, but when coupled to a known good injector outside of the engine, nothing. My known good pump turns over with a definitive click, click, click and firm detent in each position. The old pump feels weak and there is an odd noise coming from inside and it is not as springy when turning it by hand!

The car was not running fine before like I said. It was gutless, had an erratic idle and would not go past 3300 RPM. On my last trip into town, it felt like it was suffocating trying to clime a little hill! I bought an '82 300D with a timing chain so worn that once I had the valve cover off, you could see worn out links in the chain hanging there in random places and the stretch was more than 15* and it even ran better. Like I said, I will switch the pump and see what happens, but it would not suprise me is it starts.

While I'm at it, where would you go for an IP rebuild if you had to ship your pump and get it back repaired at a reasonable cost? I will be short one IP for the engine I'm rebuilding and I'm not sure I want to get into an IP. It's not like I have the tools needed anyway!

How it drove is irrelevant. Did it have a problem starting before you installed the chain?

Yes. It felt like it wasn't getting sufficient fuel and you had to hold the pedal down part way to start it.

I'm not concerned with "part way down". What was the cranking time before you replaced the chain?

5 to 15 seconds. Randomly varied in no particular order.

That's certainly not desirable...........would the time be shorter at warmer temperatures?

No shorter than 5 seconds. All glow plugs working and compression at 325/330 each cylinder. Lift pump was replaced with a new one before I bought the car.

Well, unfortunately, you've got two things going on here. One of them is preventing a start, and my guess is IP timing. The other is preventing the engine from making sufficient power and that could be anything from the lift pump to the IP or just simply late IP timing.

If the secondary filter is clean, I'd look to see what the fuel pressure is when cranking...........would confirm the suspicion of a weak lift pump.

I'll have to look at lift pump fuel pressure next, but when cranking I forgot to put the fuel return line on at secondary filter and it wasn't long before fuel was spraying out the barb fitting for the 1/8th cloth woven hose. And quite a bit of it too!:eek:

There is a tiny bleed between the supply side and the return side..........so, the presence of a fair amount of fuel at that port would probably lead me to conclude that the fuel pressure is acceptable to start.

Yeah, I thought so too! Oh, well. It's not like I have anything else to do after I get done repiping my friend Scotts house and then installing a skylight for Linda as well as redo her kitchen countertops and install new faucets and sinks after I finish building the front porch. Then I can Paint Larry's house for his wife after I finish remodeling her bathroom in the master bedroom and oh did I mention I've been laid off?:D Well, having something to do is nice. Then I can finally get around to putting the engine back into the Power Wagon and get that sold and I'll only have one other 300 TDT that I need to finish the engine for.

Other than that, pretty boring around this neck of the woods.:rolleyes:

It runs! It runs! Never underestimate the stupidity of the previous owners! IP wasn't fine.:( Maybe that's because the PO left out some "spare" parts like springs and other things I don't know the name of that are supposed to be under the stems where the High pressure injector lines go!:mad: No wonder it took so long to crank and fortunately I had many spare IP parts myself from a couple of wrecked pumps that had pumped cold Veggie Oil!

And Viola! It's Alive!!! There is a trick that took me forever to figure out from the FSM, which has really complicated instructions. If timing isn't known or chain has been diconnected or it just slipped and you have to restart, first set crank at "0" and Camshaft marks lined up properly with match,mark on cam tower. Then rotate engine for a full turn until you begin to build up compression, then stop at 25* BTDC. Now set that IP up with both marks lined up on the front of the pump. You can only see this with the IP out of the car. Now install the pump WITHOUT turning the engine to "0"! You want the engine to be in the "start of delivery" when you put the pump back on!

It will start and setting timing is fairly straight forward from here on out, just slight tilting to the engine or away from it to set correctly at either 24* or 26* which ever is your setting.:D

Great job troubleshooting!

Thanks! I cannot believe that someone would leave out a few parts and put the rest back in wrong!:eek: No winder it was a slug! I'm suprised it mran at all. You don't know how many times I almost came close to purging my parts pile of things I never thought I would use! Still have 2 of those little stems that look like plunger stops and one spring! Those will get safely put away somewhere!:mad:

Are you talking about the delivery valves? They only really serve to make the injection sequence as square as possible as well as preventing returning shock waves from damaging the pump.

Of course putting the parts in WRONG will do all kinds of interesting things :)

Yeah, that's what I mean. Just couldn't think of the name at the time, I'm terrible with names!

3 springs were missing, 2 little plungers that only open up during delivery were missing and the other was put in upside down and the round doughnut it sits in was also upside down! I was told this is why it took so much cranking to start because all the fuel drains back to the tank without those!:mad:

Runs great now!:D:flamethro