603 advancing timing thoughts... - PeachParts Mercedes-Benz Forum

locry · #1 05-20-2011, 05:08 AM

I do not remember the exact number but I have verified a few weeks back that the "notch" is visible through the IP peep hole at the "forum correct" crank pulley timing mark...

Anyway, I figured I'd experiment with advancing the timing because I have visible smoke when idling and absolutely no pulling power going uphill...

My IP is missing the adjustment screw so I'm relying on a little bit of prying power to rotate the pump(top) TOWARDS the engine to advance the timing... but it seems that the pump is already at its farthest travel... I could rotate the pump easily AWAY from the engine though.

Does this seem normal? I'm getting the impression that my pump MAY have been set too advanced? But my symptoms AFAIK indicates retarded timing does it not?

For the sake of experimenting... IF I try to rotate the IP AWAY from the engine, thus retarding the timing, what should I expect to happen at idle?

Need input guys before I button her up again...
thanks

scottmcphee · #2 05-20-2011, 09:05 AM

If you can't find a sweet spot through the whole swing of advancing the IP, maybe its time to change your timing chain. Sounds like you've twisted all the timing you can get out of the slack in your worn chain.

Twisting the top of IP toward the engine advances timing, usually getting more power until you go so much as to create knocking, then power drops off again.

You think the problem of no power is timing advance related, but it's probably just timing related - your valves are not in sync with the piston position. No amount fuel delivery timing compensation will correct that, only a new chain will get the opening and closings of the valves sync'd up to the compression stroke. When you do this, the smoke at idle goes away. Trust me, I've gone through this whole cycle.

C Sean Watts · #3 05-20-2011, 09:52 AM

I agree with Scott... check your chain and injection timing.

Diesel911 · #4 05-20-2011, 10:39 AM

If you retard the timing too much it will also cause knocking.

locry · #5 05-20-2011, 11:27 AM

Thanks for the input guys!
Will see about checking the chain for stretch, never changed it since I acquired the car, might as well change it.

What ARE the typical symptoms of a stretched chain? I do have a stumbling issue now and then...say 2-3 times during a 1hr commute at idle. Frequency increased in the past 5 mos. Never stumbled beyond that.

What's the quickest way to check for stretch?

Jeremy5848 · #6 05-20-2011, 11:40 AM

Pull the valve cover and set the crank to TDC on cylinder #1. The timing marks on the camshaft should line up. If not, you can use the degree scale on the crank to determine how many degrees you are off. Don't rotate the crank backwards and don't use the camshaft bolt to rotate the engine.

babymog · #7 05-20-2011, 01:06 PM

The pump might need to be removed and rotated one tooth in the splined-sprocket/timing device. When I installed mine, I found that I could select a couple of positions regarding the splines, found one that put the pump in the center of the adjustment range.

locry · #8 05-20-2011, 02:26 PM

All excellent info guys!!! Wow!
If the alignment marks DO line up, indicating minimal/acceptable WEAR, Babymog's suggestion will indeed come in handy. Thanks!!!

I always wondered about chain "stretch"... It never occured to me to look at it as just plain wear and tear, as in metal erosion... so that explains why not changing oil often possibly leads to "chain stretch".

When all the links of the chain "wear"... wouldn't that contribute to an overall longer chain? Just thinking out loud... I've never really measured overall length. But I do remember changing out a worn motorcycle chain, where there's noticeable play between links, I'm guessing overall length when pulled end to end will result in a slightly longer chain.

btw, thanks for the pic!
(I see we both have the same "main fan", how on earth did you get to fit that 2pc shroud in there? Mine came with a 1 pc shroud, bought a 2pc and I still can't get it to fit)

Jeremy5848 · #9 05-20-2011, 04:14 PM

My '87 came with the 2-piece shroud, probably installed to repair accident damage. I have since that photo replaced the fan and clutch with the 606-style clutch and plastic 9-blade fan. The shroud goes on easily. You drape the round section over the fan blades, then slide the rectangular section down the radiator and clip it into place. Then you move the round piece forward and rotate it so that "Tab A" goes into "Slot B."

Chain stretch also can result in worn sprockets, as those of us with motorcycle experience know. Due to my limited experience, I've not seen a worn timing chain sprocket in a Mercedes engine. AFAIK, the stretch (within limits) is taken up by the chain tensioner.

You should be able to detect chain stretch by pulling up on the chain at the top of the cam sprocket, as if you were trying to lift the chain off of the sprocket. A new chain won't move at all; a worn chain will lift up a little. More stretch = more lift. I'm sure there is a spec on how much timing error is permissible but I don't know what it is.

Jeremy

86-300sdl · #10 05-20-2011, 04:15 PM

The marks on the cam and cam tower are true points for reference but be careful about the timing marker pointing over the Harmonic Balancer.

That unit is just bolted on and has a slot to slide it many degrees before or after. I unbolted mine to clean during a recent chain replacement...Didn't think to mark it. Now I'm really not sure what it is "indicating". Some one may have done the same with yours at some time.

So if you "really" want to know if you are at tdc ya need to make sure the piston is at the top of the stroke first, then get a read on the H. Balancer indicator. If it says "0" cool. If it says "6", "6" means "TDC".

My thought was at 300k I probably had stretch and just rolled a chain on for around $115 bucks. Car runs sooo much better even though I thought it was pretty smooth before.

I do like the way you think in regards to rolling the pump to tune it by "ear". Kind of like the old distributor days

locry · #11 05-22-2011, 11:36 AM

hehe, I know what you mean... I had a hell of a time tuning a dual point distributor the first time I got one... didn't realize they were supposed to overlap thereby increasing dwell, i thought they'd just alternate to prolong point lifespan. haha... anyway...

UPDATE: it seems what little advance I did on the IP helped A LOT! My car is peppier and smoother all around. It's like the car woke up from a doobie trance!

The smoke issue is still there though... LOTS of smoke at idle at night lit by headlights... also visible during daytime as an overpowering haze... will experiment with a PVC oil catch can and see if it helps lessen the haze...

Lovin' the performance though!

ashedd · #12 05-22-2011, 12:30 PM

do you have to remove the injector lines to move the pump? Or will the IP rotate a bit with them connected?

And if you can rotate with them connected...
do you do it with the engine running?

PS:
Do I absolutely have to have an AB timing light/box to replace the IP?
cause I got an IP that has new seals I would like to use.

locry · #13 05-22-2011, 06:57 PM

I did have the injector lines in place, If you still have your adjustment knob in place you'll be fine I think. Without it you'll encounter resistance like I did. One of my lines ended up rubbing against the intake manifold...had to wedge some rubber between them to prevent them grinding.

No, I did not have my engine running... I DO remember reading somewhere that it's not safe to adjust the pump while running. I don't know why though, but better safe than sorry. (A few years back I did adjust a non-turbo 300D this way... nothing bad happened, maybe I was lucky?)

I've never seen or used an AB timing light. It was an ALL FEEL thing both times.