R107 450 1973 D Jetronic. Doesn't start - ignition timing problem?

[rowdie]

Originally Posted by Graham

Rowdie, In looking again at the pictures, perhaps both pictures are of the right hand cam. One with cam marks and one cam in general? I was confused too. Maybe szamik will confirm.

I t would be helpful to see pics of both cam marks at TDC. Rules out that problem if both are at least close.

[Frank Reiner]

Graham:

Recall that Mother Benz gives all her valve timing numbers with the valves at 2mm lift; when the engine is rotated to the point that the valve is within .006" of either leaving or approaching the seat the timing will fall in the aforementioned range.
.006" valve lift is used by the SAE in specifying gross valve timing.

[Graham]

I think we have gone off on a bit of a tangent here I take the blame

In summary,

Seems like valve timing needs attention but maybe doesn't explain why engine will not run.

Making or buying the trigger point adjustment tool or buying or borrowing a known to be good set of trigger points would help eliminate that possibility.

Seeing harness was rebuilt, maybe double checking continuity and accuracy of wiring back to ECU would be another step. And at same time ensuring harness grounds are good.

[szamik]

Hmm I think that I probably found a reason why plugs are wet and engine don't want to start. Look at these videos:

https://www.youtube.com/watch?v=JLZue_qq_yw&feature=youtu.be

https://www.youtube.com/watch?v=t9hGRMq6X4s

Sometimes spark doesn't jump between top of electrode but between plug casing. Is this normal?

Plugs are new - Bosch W7DC (non resistor), gap 0.035inc

[Diseasel300]

That's not normal. They may be fouled from not igniting/flooding. Try cleaning with a good solvent, follow up with brake cleaner to make sure any oil and contamination is washed away then try that again. The spark should always go from center electrode to side electrode (in the center like you'd expect). The only way for the spark to jump where it's jumping in your video is to have contamination present.

If cleaning the plugs doesn't help, replace them.

[Graham]

Looks like you have either the Tracking Arc or the Fouled Spark Plug as described in this link:
Figure 11 Typical spark plug problems showing damage which may indicate engine problems.

I wouldn't think that would stop the car from starting unless all plugs are same or worse. Of course it wouldn't run too well! Something else that is preventing engine from starting may have caused the new plugs to get that way?

If you clean plugs and set gap to 0.030", maybe that will help?

Those Bosch plugs should be fine. An alternative would be NGK BP6ES (I use them and pre-set gap is 0.032", I think)

Other unrelated questions:
- I remember you saying car sat unused for 5 years. Did you check the fuel tank screen as well as fuel flow rate as measured on fuel return line from fuel pressure regulator/damper? Should be about 1L/30sec with 12V on pump.
- Re trigger points, this link has more info and link to where you can get Norbert's adjustment tool or drawings to make your own. http://www.benzworld.org/forums/r-c107-sl-slc-class/2445769-trigger-points-adjustment-gauge.html

[szamik]

Originally Posted by Diseasel300

That's not normal. They may be fouled from not igniting/flooding. Try cleaning with a good solvent, follow up with brake cleaner to make sure any oil and contamination is washed away then try that again. The spark should always go from center electrode to side electrode (in the center like you'd expect). The only way for the spark to jump where it's jumping in your video is to have contamination present.

If cleaning the plugs doesn't help, replace them.

You right :-)

After night without plugs in engine (it probably was flooded by fuel) and proper cleaning all of them, engine starts like a brand new... :-)



Engine was running quite good, revs were okey and it was increasing rpms smothly but it was smoking and smelling with unburned fuel. It was running maybe about 5 min. After that I stoped it and after few minutes I tried to start again... He said - no way my friend. Again it doesn't want to start. I removed all plugs again. All of them looks like this one:



I think there is too much fuel. Don't know why. I checked both temp sensors - are good. TPS set properly, AAV works well. Idle screw is unscrewed 2 full turns. Knob on ECU in the middle of scale (11 clicks) - tomorrow I will try to start engine with knob set it maksimum counter clockwise. Injectors were checked too. They not leaking at all. Fuel preasure is good too.

Originally Posted by Graham

Other unrelated questions:
- I remember you saying car sat unused for 5 years. Did you check the fuel tank screen as well as fuel flow rate as measured on fuel return line from fuel pressure regulator/damper? Should be about 1L/30sec with 12V on pump.
- Re trigger points, this link has more info and link to where you can get Norbert's adjustment tool or drawings to make your own. http://www.benzworld.org/forums/r-c107-sl-slc-class/2445769-trigger-points-adjustment-gauge.html

Fuel tank is clean and filled with new fuel I didn't measure how many fuel return to the tank - I'll do that.
Thank you for this link.

[Graham]

Good that the engine started!

Rich running?

Check that temperature sensors are good when measured from ECU end of your rebuilt harness.

Bad trigger points will cause that condition. Believe me, I had exact that problem on my own car until I found a good used set of triggers. Later I adjusted the old ones using Norbert's tool and that set now works again. Others have had similar experience - see this link: SLC Keeps Flooding HELP PLEASE - Mercedes-Benz Forum . Trogolyte made a neat gauge here to see how long points stay closed. http://www.benzworld.org/forums/r-c107-sl-slc-class/2695945-slc-keeps-flooding-help-please.html#post14899841 Some say it doesn't (theoretically) matter so long as they open and close, but several of us have found, in practice, that not to be the case.

Idle knob on ECU shouldn't make much difference, but give it a try.

You say fuel pressure is good. Hopefully not TOO good. About 29-30psig for a start (2bar)