No spark on m116 d-jet

My car ran fine Yesterday. Now i have no spark. I don’t get 12V to the coil, With the ignition on. There is 12v from ignition on the + side of the resistor, but not much voltage after the resistor. When i try to ohm it i get 30. Is That is to much?
Is my resistor dead? Can i bypass it? To test?
Or is it an issue With the control module under the fender?

1971 Mercedes 350sl (euro m116 d-jet)

Dear Unknown,

as I see it from the pictures, you are measuring on the 0.4 Ohms-resistor. In order to measure only this resistor, detach the wires. Then the resistance should be 0.4 Ohms. Otherwise it is broken.

Regarding your voltage measurements, in the first case you were measuring on the battery side. So the 12.8 V seem to be o.k..

In the second case (on the other side of the 0.4 Ohms-resistor) it depends whether you are in the ignition or the loading mode. In the loading mode (0 V at the cable bridge, were you find the green/yellow wire coming from the TSZ-ignition switching unit) one should measure a little more than 8 Volts there. In the ignition mode there should be something like battery voltage (something more than 12 Volts).

My feeling is that most probably your 0.4 Ohms-Resistor is broken.

Good luck,
Recardo

Did a few more test. And the resistor is dead.
Is there.
Is there a Way i Can test the TSZ Unit ?

Regards. Mads

Hi Mads,
you find the testing procedure in the link to the workshop manual on top of the page under 'Repair instructions: engine combustion"
or use this link : www.startekinfo.com/StarTek/outside/1188.../M117_45/075-520.pdf

Regards
Norbert

Hallo Mads,

good to hear that my assumption was correct.

Regarding the TSZ unit, these are known to be extremely stable. So I would not expect a defect there.

But in order test it you have to find out whether the switching transistor inside is working or not. The test procedure depends on the unit which is actually installed in your car. What is its Mercedes number?

Best regards,
Recardo

Thank you for the link.
But I can't seem to find the test in that pdf, and I can't find the index page on the site, (I don't have a login) Can you help with the link til TSZ test?
I will find the part number on the unit later today.

Mads

Hi Mads,

I was away on a trip so here is my late answer. You already identified your broken pre-resistor. To check the rest, please go to menu 107 SL workshop manual - repair instructions . engine combustion . M116/M117 D-Jetronic and look at chapter 07.5-120 Testing breaker controlled transitorized ignition . Look at section standard Standard switchgear (Si). You have to turn your engine to have breaker in open and in closed position.

WARNING! If you leave your ignition ON for too long while breaker is closed, you will destroy either resistors or ignition module or coil or all of it as it will mean that a continuous maximum current will flow through these components while they normally only have pulsed current.

Hello,

only briefly: It is chapter 07.5-520.

Recardo

Thanks for all your help guys, really appreciate it.

Small update
I just ordered a new resistor and a new coil (just to be sure).

The TSZ Unit has part number 0 227 051 012, and it has a 4 fixed wires, green/yellow, Red, Black and brown.
In the cast it says 15, 16, 7

i forund the section in the manual
www.startekinfo.com/StarTek/outside/1188.../M117_45/075-519.pdf

Will try to test when I get the Resistor.

Is there a way I can test the TSZ with a multimeter, now that I have it out of the car? Or do I have to wait until I can assemble all the components?

Regards

Mads

Hi Mads,

a W116 should have a 0 227 051 014 or 0 227 051 024 ignition module. What you have is a wheel type module for R/C 107 SL. Either you swap to standard type or you have to read section about wheel type unit. It is however strange to mount that in W116. In R/C 107 it is mounted in wheel housing and gets cooled there. A 012 is potted and cannot be repaired. So keep your fingers crossed that it is not broken.

It is a 1971 350sl. Not a w116.

Hi Mads,

but then it is very confusing if you put a W116 instead in your profile. I recommend that you change that.

Car is back on the road again ! Thanks for all your help.

Just godt the resistor today. Also changede Coil, Rotor and cap. I have a also ordered a new set of wires.

Mads