Timing chain issue

[Novamonte]

I have replaced a leaking head gasket and am putting everything back together. I have only just now learned that the bolt in the chain gallery that holds the servo steering fluid container bracket in place also secures the chain from slipping. When I turned the engine (by hand using a socket on the craknshaft pulley) that bolt was out and the tensioner was not in place, so the chain seems to have slipped two teeth on the distributor/IP drive sprocket (I remember hearing two clicking sounds when I did this...). The crankshaft is on TDC and the cam lines up as it should, but the rotor arm no longer points to the mark on the rim of the distributor as it did when I took the cylinder head off.

What is the easiest way to correct this? Should I take the cam sprocket, the tensioner and possibly the other small sprocket above the distributor/IP drive sprocket off and try to move the chain back in the right position on the latter or is it better to take the distributor off, take the drive axle out and reposition it and take the IP off and re-time it? Any advice from those having experienced similar issues would be appreciated.

[ctaylor738]

If this happened to me, I would keep the engine at TDC. take the distributor out, fish out the drive gear, and reposition it so that the rotor is pointing at the mark as before.  Then I would move the crank to 20 after TDC, remove the pump, re-time it, and re-install.

[ja17]

Hello,

If the chain has slipped on the large sprocket in the block, then the distributor and injection timing is now off.  If only the small distributor gear (under the distributor)  has moved only the distributor will be off.

[Benz Dr.]

I can't see how the chain would slip over such a large gear. If the chain is really worn out and the gears are also worn, then maybe it could do this. If it really did slip, you have other things to look at.

[Novamonte]

Thank you for the quick responses. I can't be sure that it was the chain slipping, I didn't know that the axle under the distributor can slip as well when the engine is turned. As I don"t know whether only the distributor is out of timing or the FI pump is as well I assume that the only way to be sure is to reposition the shaft under the distributor and remove the FI pump to check timing. Given that the injection lines, the coolant hoses  and the linkage are all already disconnected that should not be too difficult I assume.

[garymand]

I'm with the DR.  Very interesting.  Your description is strange.  There is a bolt near the distributor that drops down through the head and a bracket that braces the power steering reservour.  BUT that has nothing to do with the timing chain. 

I can't think of anyway the chain could skip teeth on the disty but not on the cam.  Unless you had slack in that area and not on the chain tensioner side.  It may make sense that as you moved the chain to remove the head or as you installed the head and connected the chain, the chain slackened on that side and as you took the slack out you moved the disty drive gear.  NJow to reverse the proceedure.

  I would rotate the engine to get the spark back to mark on the distributor (it's TDC) and see how far off the crack and cam are from their TDC.  Then to be safe, if there is any chance a valve can hit a piston, pull the rockers on any of the valves that are open or near open.  If you need details let us know.  What you are going to do is disconnect the chain and give the distributor slackso it doesn't move while you move the cam and crank to TDC.  Time the crank and time the cam. Rotate the engine to TDC, ensure the cam is at TDC.  You have to determine which way to go.  Did the disty fall behind or jump ahead?

[Novamonte]

There are two bolts holding the reservoir. One goes down the head and the other, larger one goes through the chain gallery. I understand that this is the "special bolt" with a rounded, hardened tip that secures the chain from slipping. There are some posts on this "special bolt" on the forum. I have turned the engine so that the distributor points to the TDC mark and the mark on the cam washer then appears to be more or less exactly two teeth off.  The rockers are still off after the head gasket change, so no risk that the valves hit the pistons. The distributor has fallen behind. I will try to do as you propose and give the chain some slack around the disty/FI pump sprocket and move the rest.

[garymand]

Very good.  Its staright forward when the lifters are out.  Just line up the 2 marks and 0 (TDC) on the crank.  You have not lost track of where the FIP and spark are.  If you don't know about the big gear that drives the disty, it is all too easy slip the chain down past the gear and then move the gear as you take up slack.

[Benz Dr.]

Lets assume that the crank and the cam are in time. A visual inspection should tell you that.  The only way the pump can go out of time is if the gear moves and I doubt that it did.  That leaves the distributor which is more likey to be out of time.
Remove the distributor and use a large screw driver to turn the drive gear that's inside the distributor drive housing. It will only turn one way easily - turn it in that direction. THe gear will move up and then back down again as the teeth come into contact. Check the position of the distributor each time you turn the gear until you have the distributor in the right quadrent.  The vcuum cell should be pointing towards the rad and the upper rad hose. As long as the rotor is pointing towards the notch on the top of body of the distributor it will be close enough to start the engine.
If you think the IP is out of time check it now before you go any further. 
 

[garymand]

I think he did move the gear when he reconnected the chain, because the disty is not timed to the crank, the cam doesn't matter at this point.

I think we should recap, this could be very confusing to someone who slipped his timing chain during a head job.  And potentially he could lose his FIP timing by moveing the disty independed of the FIP.  Are not the FIP and the disty driven by the same gear?  Maybe I missed something. 

He has not said he removed or otherwise changed the disty position (relative to the FIP).  If true, that is a very good thing, because the rotor position tells us where the FIP is.  You can't change the disty position relative to the IP without lifting the disty.  He has said he had a problem with the timing chain he didn't say he moved the disty.   

(As I remember, the timing chain turns a gear that is the common driver for 4 things: Tach, oil pump, FIP, and Disty.  The timing of the FIP & disty are mechanically related and synchronized through this connection to the timing chain.)

If he has not lifted the disty then the relative IP & disty timing are still synchronized and idicated by the rotor and disty mark for #1 spark. 

But, if he now lifts the disty and changes its rotation relative to the FIP, he will loose the known relationship of the FIP and the mark on the disty, oops, the IP timing will be lost. 

It was my understanding that he removed the head and when reinstalling the chain, (he didn’t say how), he found the disty mark is no longer sync'd with the crank, (since the lifters are out, the cam is not a problem and is easy to resync).  His problem is how to resync the crank to the FIP & disty.  If that is accurate & he has not disrupted the disty/FIP connection, he is in luck and can re-sync the crank to the disty.  Since, you cannot rotate the FIP by turning the disty, you must use the crank to position the disty rotor to the mark, then realign the crank to TDC by slipping the chain around the FIP/ disty drive gear, as you rotate the crank.

[Novamonte]

Correct, I never lifted the distributor so I have also assumed that if the distributor is off the IP must be as well. But from some of the answers above I got the impression that the disty drive axle can slip and somehow lose contact with the IP. Be all that as it may, I decided to check pump alignment just to be sure now that it is anyhow disconnected, but I found it difficult to get to the nut under the pump as the oil cooler connections are in the way (I understand from other posts on the forum that this is a problem on the M129 engine with the flat oil cooler). I will keep trying tomorrow with a long extension and possibly a universal joint. That nut is the only thing keeping me from taking the pump off.

[ja17]

Hello Garymand,
Remove the fuel filter canister and reach the lower nut from under the car.

[Novamonte]

Thanks! I had begun to think about trying from underneath, but removing the filter canister will of course make iit a lot easier to get access.

[Novamonte]

Removing the fuel canister did the trick - after that I was able to get a ratcheting box wrench around the nut without having to go under the car. Next problem is that the pump won't come off. I think I have reconnected everything - fuel lines, oil line, injector lines, coolant hoses and wiring to solenoid. I can twist the pump a millimeter or so but it won't move backwards off the drive axle. Any thoughts? Is it just a matter of brute force or is there a trick for doing this?

[ja17]

Check the back bottom of the injection pump. Most have a support bracket which connects to the engine block.

[Novamonte]

Thank you - I found the bracket (and am a bit embarrased for not having thought of that as it is in plain view on the pictures of the injection pump in the technical manual). The problem is that it seems almost impossible to get to as the oil cooler is in the way. I will put the car on the axle stands tomorrow and see if I can reach it from below as I have not been able to get to it from above. Question is if it is worth all the hassle just to check pump timing. I have read some posts on that and understand that the pump timing is not very critical at all. If the timing is off it is not by much as the chain can't have slipped by more than two teeth. Any thoughts on this (and how to get to that bolt) would be appreciated.

[ja17]

Yes, pump timing on these engines is not that critical. Yours is probably not off enough to make any noticeable difference. In any case, the bracket bolt is best removed from below.

[Novamonte]

Today I finally got the IP out, but it wouldn't give up without a fight. I removed the oil filter canister to get access from below and was able to get the bolt holding the bracket out. There was no room for a socket wrench and the ratcheting box wrench would not work since the u-shaped cross section of the bracket made it hit the button on the wrench when I turned it and changed the direction of the ratchet.. The shape of the bracket also prevented the use of a regular flat combination wrench, but an angled box wrench did the trick. Next problem was that the bracket hit the water hose going from the block to the oil cooler, so the pump would not come free from the upper stud. Hose had to come off and so did the pump finally. I took the stud out to make assembly easier and intend to put it back with the IP in its right position.

I now understand at least one of the reasons why Daimler discontinued the flat oil cooler... As expected the pump was about 45 degrees off timing, so it is now clear to me that the chain can slip if the "special bolt" and chain tensioner are not in place when the engine is turned.

Thanks everyone for helping out. This forum is really fantastic and I have learned so much from all those experienced members.

[garymand]

Sorry I didn't see your struggles with the pump sooner.  It is not possible for the FIP to move relative to the distributor unless you break the internal mechanical shafts or gears.  Yes, the FIP needs to be timed, BUT the disty rotor is indicative of the FIP timing!  Lesson well learned.

[Novamonte]

Thank you Gary. This will also give me the opportunity to clean the pump and make it look much nicer, and to paint the block also behind the pump.

[garymand]

And besides, now you know how to time the FIP!  That's have the fun of these cars.