I have this 91 500 sl
with a no start condition
has fuel pressure but no spark
coils check ok but no signal to collaps field
checked inputs to ignition unit appears to have inputs
only thing is when cranking voltage drops to coils &unit
is there a connector or ground I should check

thnks pwder

The ignition module requires approx 3-4 amps of power from the IGNITION switch to create the dwell signal to the coils. OF course the crankshaft sensor must create an AC waveform to the ignition module as well.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Just wanted to thank you for the reply. I rechecked my crank sensor pattern and it was fine. then I tapped in to the power feed line before the ezl unit and it would have 12v unplugged.
Then when I plugged it in it would dropped to 4v. Anyways I
I found the voltage drop across the ignitoin switch. I bypassed the switch with 12v and it started. the new switch will be here tomrow.
thankyou again for your help. I am a honda master, toyota master,ase master diagnostic. I have about 2 years a mercedes
dealer but now I am at an independant and getting technical
info on mercedes is hard to come by for me . If I could email you for from time to time with a ? or if you could give me an idea where to find some info it would be greatly appreciated.


Thanks again brain b

You've probably found the best place for info right here . Seeing as how you are a tech you maybe should email Benzmac and get set up as a "tech". Also, don't forget to share your experiences with others as you can. I may have a Honda question every now and then.

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Jim