350 SLC 1972 troubleshooting

Hello again,

I have been investigating a little deeper my ignition timing issue.
I have also notice that the 1st and 5th cylinders were misfiring.

The spark plugs of cylinders 1 & 5 are wet (from fuel ?).
As you can see in the following picture with cylinder 2 plug on the left and cylinder 1 on the right.


May be the plugs are defective.

I have put the cylinder 1 plug to the cylinder 2.
And the cylinder 2 plug to the cylinder 1.
Restart the engine. Let it idle a little bit.
And check the plugs again.
The new cylinder 1 plug (previously cylinder 2) is wet.
The new cylinder 2 plug (previously cylinder 1) is dry.
It is not coming from the spark plug.

May be it was coming from the high tension wires.
I did the same test by changing the cylinder 1 wire to cylinder 2.
And vice versa. The results are the same. cylinder 1 plug is wet, cylinder 2 is dry.
It is not coming from the wires.


I have also test again the ignition trigger wires between the distributor and the ECU connector.
Also tested the injector wiring resistor value between 1.2 and 1.4 ohms on all injectors.
All is fine.

I checked the distributor head.
There was some cracks in it.


There is also some marks, like if the rotor was touching the head.


On the opposite side of the distributor (wich are cylinder 1 and 5) it is like the rotor was touching below the contacts.
There is also some minor scartch marks just below the contact points.



I had also 2 used distributor heads as spare.
I try one on the car and start the engine.
I had the same behaiour with misfire (no fire) on cylinder 1 and 5 (wet plugs).

Today i descided to remove my distributor to check it outside the car.

I have notice some play (and no it is not the centrifugal advance) in the rotor.
Remember my distributor is equipped with a pertronix ignitor instead of the points and condenser.

When i remove the ignitor magnet, and put back the rotor.
Ther is no more play.




With the magnet in position, the rotor is not in the correct position on the distributor shaft.
It is not low enough on the shaft. You can also see some orange bits inside the distributor.


With the ignitor. the rotor is at 53.44mm.



Without it is at 52.19mm.


You can aslo see some scratch inside the rotor.


The play in the rotor may be the source of my ignition timing delay.
Remember i had to add 8° to get a fully reving engine.

With the car spare parts, there was a used points and condenser.
The condenser is the bosch reference 1 237 330 306, and it had the typical mercedes green wire.
So i assume it is the correct parts for my car.
There is no reference on the contacts, only 'VEMO'.

I will try tommorow to install it back on the distributor, set the dwell angle and set the timing to the factory value to see what happens.

If anyone as got some picture of the original contact install within the distributor it might help.

Hi Sylvain,

i will add a photo of a disassembled distributor here. I do not understand why people would install a Petronix on a car with ignition control module. Maybe someone was desparate with the wrong retard connection. However, I recommend to use Bosch rotor and cap and NGK spark plugs and Beru ignition cables. Beru has sometimes caused troubles with rotor and cap. While Bosch is known for trouble with spark plugs from free market.

Hello Volker,

Thank you for the picture.

I have NKG plugs already.

The current rotor (VK283Pip) and cap (VK283Phv) are made by BERU.
I will try to find Bosch parts.

I will check the ignition cables tomorrow.

The ignition cable are from Beru (ZLE 121).

I have put back the contact points and condenser.
I set the points to 0.4 mm and verify the dwell angle when started.




The condenser wire have been modified but it should not be a problem, I hope.

I will use the following diagram to connect the condenser / point wire to the switchgear.