Trigger Point Conumdrum

Oh I had the air temp disconnected because I had the air filter off - I’ll have to check that one again (just checked and it is 427 Ohms @ 11 degrees C - At specs ). So having this disconnected could impact it starting?

Pin 18 - Do I need to check this between Pin 18 and Pin 50? (if so where is PIN 50?)
Thanks
Peter

Hi Peter,

I do not know what you talk of pin 50. pinout is here jetronic.org/en/d-jetronic/pinout#mb8

Hi,
In the connection column of #18 on the 'check-list' it states - start signal (to pin 50).. There is not much information on exactly what the start signal and associated components do? So I was wondering how to check this further?
Regards
Peter

Hi Peter,

well pin 50 is the German standard number for the starter. It has nothing to do with D-Jetronic. This pin 50 on starter is connected to pin 18 of D-Jetronic ECU. Measure against ground pin 11. While cranking engine it should show +10-12 V.

Hi,
Thank you - sorry to be so difficult but I really appreciate your help. And not to be even more difficult than I already am but am I correct in that this issue with pin 18 is an external issue and not to do with a problem with the ECU? I guess what I want to know do I look for an issue with the ECU or at an issue with the starter circuit???
Again
I am sorry for being so slow
Peter

Hi Peter,

it is an external signal from starter that the ECU reacts to. Some immediately with start enrichment, some like yours with after start enrichment. But all do start the injectors no matter what trigger points say. That signal is also used for thermo time switch and cold start valve.

I was looking at your site that listed MB part numbers for a throttle switch (1973 slc 450) but I couldn't find mine listed. On the PCB it is 1288 310 023 Is this just the PCB #. And if you were going to replace one would a Bosch 0280120029 fit? I think this is off a 280 sl/c m110. But it states it will fit a 450????
Regards Peter

Hi Peter,

that is just the PCB. The Bosch no is engraved of the back of the T.C.

Hi Just a little update. I got the Throttle switch working and tested the pin 18. At the top relay I am getting over 12 V and at the other relay (directly below) I am getting about 9.5V and this is the same reading I am getting at the ECU.
The spark plugs seem wet.
There seems to be a spark (jumps about 13 mm on Spark plug Tester)
I hear clicking of the injectors when it turns over.
The engine is at TDC (bunny ears poking up) and gap is just over .3 mm (Ive tried slightly both sides).
Ive sprayed fuel and starter fluid into carby and cylinder but still if doesn't fire???
It is a conumdrum

Hi Volker,
I have just had a thought. The diagram of the trigger points that you posted (with the oscilloscope). Are these in chronological order of firing (don't worry about a starting point) and do the colours match the wiring colours.
Eg;
White
Blue
Red
Green

Thanks
Peter

Hi Peter,

yes the diagram I posted is in sequence of firing. But colors are selected by oscilloscope, have nothing to do with wiring harness.

When you have wet spark plugs, then either they are dead (swap with new NGK ones) or ignition does not operate as it should or mixture is far too rich. Spraying start pilot will then not help.

Any issue with this - tested the pin 18. At the top relay I am getting over 12 V and at the other relay (directly below) I am getting about 9.5V and this is the same reading I am getting at the ECU.
Thanks
Peter

Hi,

pin 18 should show 9...12V while cranking starter. I do not know what you mean by 12V at top relay. If you talk of cold start valve relay, that has nothing to do with it.

Hi,
These are the 2 I tested. So 9.5 volts should be fine?
Thanks

9.5V is fine for ECU. I cannot believe that line 50 from starter shows 9.5V on relay 4, 12 on relay 2 and then again 9.5 on ECU. Or maybe I do not get you right.

Hi all (especially Volker),
I promise this will be my last 2 questions (for awhile at least) and then I will leave you alone.
1/. On the Trigger point actuators that touch the cam - does a short length (say 1.8 mm compared to 2.4mm) increase the injection amount (points are closed longer and therefore injecting more fuel) or is it the opposite?

2/. What would cause the spark at the sparkplug to jump to the body of the plug and not the tip?

Regards (and thank you)
Peter

Hi Peter,

the ECU does not care for dwell of trigger contacts, it just triggers ona closing contact (falling edge trigger). This is not like in ignition where dwell determines the chariging of ignition coil.

Spark always moves along the path of least resistance. So if tip is cloaked with something, it might go to spark plug housing instead.

cjhols schrieb:
1/. On the Trigger point actuators that touch the cam - does a short length (say 1.8 mm compared to 2.4mm) increase the injection amount (points are closed longer and therefore injecting more fuel) or is it the opposite?
...

Hi Peter,
in addition to what Volker said:
With the actuators worn down to 1.8 mm the points will not open anymore. When they still do, they must have been readjusted.

This would be o.k..

Did you use my tool or did anyone else readjust them?
Did you clean and regrease the camshaft, especially remove rust?

Do you have the plastic hoods covering the points? When readjusting the points so much you have to take care the hoods don't come in contact with the distributor camshaft. The hoods would be destroyed then.

Regards
Norbert

Hi -yes I did use the tool and it worked a treat. The actuators seem to be working ( with a multimeter) I just had a thought that if they were closed for longer it might produce flooding.
Thanks
Peter

Sometimes there is no rhyme or reason for things. I cleaned 2 spark plugs and opened the gap on one and low and behold the car ran - not well mind you. I had to give it full throttle to start it and then it did its usual warm up (high revs).
Unfortunately, after that, whilst idling, it slowly died and eventually stopped. I could start it again but the same thing happened (without the warm up revs) and lasted for about 1 minute. I could keep it going if I gave it more throttle but it wouldn't hold idle.
I did try to adjust the air/fuel mixture but this didn't seem to help it idle. The timing is set at 5 degrees BTDC with the Vacuum advance on but the distributor stopper bolt won't allow me to adjust it any closer to TDC.
Could it be the notch adjustment on the Throttle Switch stopping the car from idling?- I did have this off
Or could it be the distributor points adjustment.

At least we are getting somewhere.
Thanks Norbert and Volker