My 95 C280 will not start at all, not even a hint of the engine turning over. The starter cranks the flywheel but the engine does not start. I checked that there is voltage going to the ignition coils packs; And these are 3 new coil packs that i just installed. But there is no spark at the plugs, not even one of them. Can anyone help with advice? I'm kind of at a dead end now, not really sure what to do next.

 

I'm not familiar with cars of that vintage, either I work on classic cars or modern cars but, if it's fuel injected, it gets a signal from what is called a crank position sensor. This sensor sort of replaces the old distributor used in antique cars and sends a timing signal to the ECU telling it when to fire a spark plug and when to open an injector. On MB's it's typically by the flywheel on the drivers side and is fairly easy to replace but you'll need patience. Also, part is fairly cheap in aftermarket. They've used the same part for many years and it's a very common failure point MB's (as is anything piece of Bosch feces).

 

I changed the crank sensor with no good result. I'm starting to think I may have a bad connection somewhere. This is a used motor that I put in the car. There is a ground wire connection that goes from the frame of the car to somewhere else, which I'm not sure of anymore. It is on the rightside of the transmission, looking towards the back of the car. If anyone has a c280 and can take a look at it for me, I'd appreciate it.

 

why not just check the wiring diagram?

then check the values of ignition coil, etc.

 

There is voltage at the coil (11 volts) with the key in the ON position but the car will not start. I have the wiring diagrams but quite frankly, I'm not an expert at making sense out of these diagrams. Also and I forgot to mention, when I turn the key to the ON position, I can hear the battery humming loudly. Seems like something is drawing power from the battery.

 

Friend of mine had this problem on his C240. When he jump started his car it ran for a little while and then he couldn't start it again, even with a new battery, it would crank but no spark at the plugs. It turned out that MB has fusible links the wiring that tripped, sort of like backups to the fuse box to prevent engine fires. Also, a wild guess, could this be some anit-theft feature that has tripped? Also, when you say "used motor", has this ever worked in your car or are you trying to get it going for the first time?