This is easy. You either test or have someone else test. Can you test???
If you can't find any relays, I would have someone else test. First test is what is missing. Do you know what needs to be there? Spark, fuel, compression, and the timing of such. Which is missing? From the previous replies I'm only guessing that the starter works.
Bosch Master, ASE Master, L1
33 years MB technician