another chain question - Page 3 - PeachParts Mercedes-Benz Forum

JimmyL · #31 02-12-2006, 09:43 PM

Quote:

Originally Posted by wade

hello again!!! trying to get my old 240D on the road (actually the car runs great)

I go back to your very first post. The car runs great. It currently runs great without spending a dime to get it that way at this point.
There is a 100% chance I would just drive it this way until something changed. you could be in for quite the expensive dissaster, if things go like things often go.
Think about it.......

Brian Carlton · #32 02-12-2006, 09:54 PM

Quote:

Originally Posted by wade

so can you explain to me how the car would not run poorly when you change
the cam timing that much,and not change when the fuel was injected. Or additionaly,if the car runs very well now,how could it not run worse if you changed the cam timing that much and left everything else alone?

The vehicle will run poorly. You can't just leave it with one tooth retarded. You'll be somewhere near 10° or 12° retarded. Then, you can determine you exact stretch of the chain.........and.........if it's really bad.........you may elect to install a new chain to return it toward the proper spec.

If you are going to simply rotate the cam sprocket by 18° and leave it that way, it will probably barely run at all.

Either you go the whole route and deal with the issues, or just leave it as it is and accept whatever chain stretch that you currently have.

See Jimmy's post above........it makes a lot of sense.

wade · #33 02-12-2006, 10:31 PM

great advice boy's.......if i had a dollar for every hundred i spent fixing a mistake that didnt need fixing(well you get the picture) this is my 3rd mb diesel and it runs the smoothest and the best by far,who knows why its that far out,but i am thinking that i might take the
"if it aint broke dont fix it route" I guess i just like to have things set up right, and thats the part that bothers me.
I just hope the chain is not at the point which it may break,i know its rare but that was the whole reason for checking it to begin with.

thanks for all the help (amazing resource site

)

wade · #34 02-13-2006, 11:03 AM

one last question regarding this. if for whatever reason the PO advanced the timing by one tooth (18 degrees) what would they have done to have made the car run so well. I am assuming like Brian says,that if you retarded the timing 18 degrees the car would barely run. would the same not be true if you advanced the timing that much,like the PO probably did.

Brian Carlton · #35 02-13-2006, 04:35 PM

Quote:

Originally Posted by wade

one last question regarding this. if for whatever reason the PO advanced the timing by one tooth (18 degrees) what would they have done to have made the car run so well. I am assuming like Brian says,that if you retarded the timing 18 degrees the car would barely run. would the same not be true if you advanced the timing that much,like the PO probably did.

It is certainly odd that it runs so well when the timing is 13° early. If you were running 13° retarded, the engine would not run anywhere near as well.

Have any fuel economy numbers for it?

Does it start easily at all temperatures?

It's quite the curiosity factor.

wade · #36 02-13-2006, 07:27 PM

yea, the car starts great when its cold, -12 degrees celsius and it starts no problem my other MB diesels did not have the same success.
as per fuel economy, i am consistantly getting around 35 mpg on a combined city highway type enviromnent. that is imperial gallons however, so
probably around 29-30 US gallons.

wade · #37 02-14-2006, 03:19 AM

I gotta tell you,this problem is driving me crazy. I cannot leave it alone!!!!
I stopped by a MB specialty shop today and told them about my problem.
This old dude who has been twisting wrenches on MB"s for a million years
said that there is no way that this car (he heard it running) has the cam timing out by 12 or 13 degrees.......as Brian said advanced or retarted by that much does not reveal an engine that runs as well as this one.
So i dont mean to revive this thread,but WHAT IS GOING ON!!!!!
I cannot accept that i have some magical motor here.dont get me wrong. i am happy that it runs well,i just want to understand WHY it runs so well......
for most of us on this forum, it is more of the game and understanding what makes these things tick, then it is to actually have a well running car.
so.....what issues could make this car purr with the cam timing being out as far as it is?
to refresh: cam marks lined up,crank mark is at 10 BTDC
2mm intake check: crank mark at approx 2 BTDC

Brian Carlton · #38 02-14-2006, 10:00 AM

Well, we first need to agree that it cannot be running at 13° BTDC. Personally I find it odd that it will run well here, but, have no personal experience.

So, before we take the opinion of a single old guy, we had better get some feedback as to opinions whether the engine can run well at 13° BTDC as compared to a specification of 0°. (or, if you prefer, running at 2° BTDC with a specification of 11° ATDC).

If we agree with this, then it becomes necessary to verify that the cranksaft damper is at 0° when the #1 piston is at TDC on the power stroke. This is difficult to do but possible with the correct equipment.

wade · #39 02-14-2006, 11:33 AM

i had asked the question before, but like you said i think it may be difficult to do. How do you determine tdc on #1 if you cannot use the crank indicators?

Brian Carlton · #40 02-14-2006, 11:44 AM

Quote:

Originally Posted by wade

i had asked the question before, but like you said i think it may be difficult to do. How do you determine tdc on #1 if you cannot use the crank indicators?

I think Larry has done something of this sort. I'm going to try and get him to post.......if he cleans out his PM's. I'm not sure if you have to pull the prechamber to get to the top of the piston.

#41 02-14-2006, 12:28 PM

To begin with I am skeptical of the 13 degrees being correct, not because I don't think it would run well, maybe it could be tweaked around to make that happen if it were possible for the valve timing to be that far off. You have to remember that this is a diesel engine with better than 20:1 compression. That means that the combustion chamber is microscopic in size. THAT means that if the valve timing is very far off you will have valve to piston contact.

If the valve timing is retarded you will not have near the chance of valve piston contact as if the valve timing were advanced.

Now for finding top dead center. In a gas engine this is very easy to do with the head on by making up a positive stop out of an old spark plug and screwing it into the spark plug hole.

With this engine, however, both the injector and the glow plug, the only accessible holes into the cylinder, go into the prechamber, thus you can't thread something in to use as a positive stop.

The other alternative would be to tighten a valve down somehow to use as a positive stop and I'm sorry but I'm not taking such a risk with MY engine. It would be too easy to bend a valve.

All that said, the markings on the harmonic balancer are pretty darn accurate on these engines. I believe that I would pull the crankshaft bolt and look to see if maybe the balancer is not keyed in correctly. Unfortunately it is all too common to see balancers improperly installed on these engines. It could be that some gorilla forced on the balancer and it is off by 13 degrees or whatever. That would explain the engine running well while the marks are not aligning properly.

That said, if the IP timing has been checked and is correct then the likelihood of the balancer being the problem decreases, but it is easy enough to check. Pull the crankshaft bolt and see if the dowels are neatly in place.

Good luck,

t walgamuth · #42 02-14-2006, 07:32 PM

and i was thinking that perhaps the cam is off in its mark. if the cam was an aftermarket or reground or some wierd thing like that.

if off that much it should not run well.

tom w

wade · #43 02-15-2006, 03:36 AM

i am really caught between a rock and a hard place here. Just came out of work tonight,and we are having a bit of a cold snap (7 degrees F) and of course the plugins were not working. The engine didnt even turn over 1 time after just 1 cycle of the plugs and it started and ran like it had been running for an hour,no missing or smoke or chugging. This whole can of worms was opened when i checked the stretch after adjusting the valves (which really needed it by the way) and if i thought it ran good before,man what a difference with the new valve adjustment.

So my issue now is.....do i just leave it alone or try and find out why the crank marks are so far out? i would hate to jeopardize the best running MB i have ever had, but then again, i would love to find out why my readings are so far out of whack.

I am not sure what i expect to gain from posting this thread, i think what ever has been said is all there is to say. But i have always thrived on having my cars set up the EXACT way they are suppossed to be set up. It has been made very clear from all the MB experts both on this forum and around town, that there is no way this car is running with the timing that the crank and dial indicators say it is. So..............should i mess with it? i guess the question should be
"do you want a great running MB diesel, or do you want to sleep at night?"

t walgamuth · #44 02-15-2006, 05:24 AM

up at night, i would do what larry said. pull the pulley and look at the dowells.

otherwise i would enjoy.

tom w

Ralph69220d · #45 02-15-2006, 08:08 AM

I might get a lot of laughs with this suggestion, but here goe's anyway. To find TDC on cylinder #1: Pull the glow plug. Fill the prechamber (hence, the cylinder) with heavy oil. Rotate the engine by hand very slowly until the oil stops emerging from the prechamber. That's TDC.