420X2

I have a 1994 S600 coupe that cranks and will not start. So far, I have verified that there is spark getting to the plugs and fuel getting in the cylinders.

I have looked at various posts here as well as gone through the Mercedes Service Manual (the virtual machine software you can buy on eBay) and now it appears it is down to the Ignition Control Module (ICM) or the crank position sensors. Considering the price and availability, I prefer to start with the crank position sensors. Does anyone know how to test these to know if they are the issue?

How about the ICM: how do I test that?

By way of background, one day in February, I came out to start the car and out of the blue it would turn over but not start. There were no hints of any issues prior to this. It just cranks and won't fire up. While wondering what it was, and trying to start it every now and again, about two weeks later, out of the blue, it just lit up and ran fine until a week ago. Now, I'm back at square one, with a freely cranking motor that won't fire up.

Plutoe

Post your VIN!!

420X2

Oops! I am at work and don't have the information handy. I will follow up this evening when I get the information.

420X2

Vin is WDBGA76E1RA168629

Plutoe

Well bro,if you don't know the diagnostics on this monster, I feel for you---in any event if you have a pluse tester--24 is a bad L or R CPS--if you don't know what that is use a multi meter and if you get > .35v the CPS's are good.

PS: I think you are going in the wrong direction,but without the applicable diagnostic tools--good luck!!

420X2

Once again Plutoe, thank you for your advice. I don't know what a "pluse tester" is, so it goes without saying, I don't have one. I can check on the voltage per your instructions with a multimeter though. To be clear, do I test that with the ignition set to "on" or do I need someone in the car actually cranking it while I measure with the multimeter?

You mentioned you think I am going about it in the wrong direction. At the risk of sounding naive, what do you think I should do differently? I'm open to any idea (within reason!) you may have. Thank you again for taking time to help me on this.

pncurtis

This almost sounds like it might be temperature related. Do you recall the approximate temperatures in February and last week? Perhaps you should ask a good Mercedes mechanic for some assistance as it may reduce your grief level considerably, particularly if his experience helps him to know the problem based on your symptoms.

All the best,

Paul Curtis

420X2

Paul,
Thank you for your suggestion. However, I am positive it is not temperature sensitive. In February, when it first happened, it was quite cold and wet. The other week, it was quite warm, sunny and basically, the opposite weather and temperature conditions.

For me, this is a hobby car, not a daily driver, so if it takes me a month or to to figure out, so be it. For me, half the fun is to take it apart, figure out how it works, and put it back together and feel a sense of accomplishment. Taking it in to a Merc mechanic is my last option. I only use it when I get to the point where I have done all I can do, picked the brains of those who are wiser or have more experience than me, and still can't get it to go. Sometimes, it's a matter of necessity, like when the Mrs. says, "enough, get it going Mr.!" In other words, I like to make sure the horse is good and dead before I call for professional help. It's almost like giving up and I hate doing it.

However, she is patient with me, so I have time before it comes to that

420X2

Plutoe, do you mean one of those little boxes they sell on places like eBay for about $40-50 that blink a light when you plug them in, where you need to count the blinks, then wait a few seconds between blinks, and at the end, if needed, you can clear the codes with them? It just occurred to me you meant a pulse, as in light pulse tester, is that right? If so, I may spring for one, given your very informative responses to my other post.

For everyone else, out of the loop, Plutoe was giving me some pointers on getting a DAS Xentry system to properly connect to the 38pin CAN connector in the engine bay. The only issue is the insane costs associated with those; but they look really cool. In time, it will happen.