jacobdeim

OK I've done a good bit of searching but I've hit a dead end. I have a 1998 e320 with a no crank, no start issue.
I've jumped the starter relay (k40 relay i believe) and the engine cranks good but doesn't fire, so it can't be the battery or the starter.
I tested that relay and switched it out still nothing. Tested every fuse I can find all good. Also both in park and neutral won't crank in ether.
I've been referring too a starter wiring diagram I found online. It shows a violet wire going from the ignition switch to the pcm for the start signal, tested power at that wire, no voltage in start position.
I tried jumping power to that violet wire to 'trick' the ecu into starting that didn't do anything.
So I'm thinking I'm down to it ether being the ignition switch, the key itself or a wiring issue. But I need a wiring diagram to go any further.
Thank you for reading through this any advice or tips would be appreciated.

jacobdeim

Update, car decided to start up now that I got the shop warmed up, I believe it might be related to the cold weather we've had.

Also with it warmed up if I tap 12v to the violet wire it with the key in run position it starts up. With that detail I'm inclined to believe when I tested that I had a bad connection.

Is there anything in the wiring for the pcm that could be effected by temperature or is it 100% the pcm.

Plutoe

Assuming you have all the correct/applicable fluids and a well charged battery the car should crank/start at -30F-----you have other issues!!

jacobdeim

I know it should start. What I was asking in the last post is whether it sounds like a faulty pcm or could it be something else?

I'm leaning towards the computer itsself being bad.

Does anyone have a pin out of the ecu for this model so I can make sure its getting proper power and ground when I'm having this issue?

Ubuy Usave

Same issue with My 2000 e320. k40 module or starter relay were suggested to Me. Have a mercedes master mechanic looking at it now. Will keep you updated. He's jumping it from the right side by the k40 module but it isn't turning over either, just cranking.... and it seems while its been sitting I developed a gas leak on the driver side... when it rains, theres a monsoon

jacobdeim

Let me know what he finds out. Thank you.

Ubuy Usave

After running a diagnostic, he says either the computer has an issue or the transmission that was recently replaced is the reason behind the starter not being sent the signal. Having it towed back to mechanic that installed tranny to have him see what he can find. Also have to replace the gas tank now, still don't understand why it was sitting for over a week and then decided to leak.

jacobdeim

Thanks for the reply. I'll let you if I find a fix. I'm trying a different ecu but have to clone the original because of das. Fun fun. Looking comparing the new one to the original now too see if I can find any bad solder joints for a quick fix.

Not sure how the trans could cause it unless the neutral safety switch was installed incorrectly. Good luck and let me know any progress.

jacobdeim

My problem ended up being the k40 relay. I thought I had eliminated that as a issue but....

I took apart the relay and can't find any bad solder joints. But as I said before when the vehicles at room temp it starts. So I left the car in the shop and put the k40 relay outside. When I reinstall the k40 cold it won't crank. When gets up to room temp it starts... Did they figure out yours?