Hi folks.

My name is Chip Quinn, and I have been involved in hot rods and racing car stuff all of my life. I currently make my living building hot rods and components from my small shop in downtown Phoenix. Lets just say I'm a fairly sharp car guy! But, all of my experiance is with vintage American stuff- you know, V8s, points ignition and carburators...

None of all of these traits however has equipped me properly for the spector of a mess I have sitting in my driveway today. My Girlfriend LOVES her little SL. I told her about three years ago when she purchased it that I would do maintance and general repairs, but that my knowledge of computerized ignition, and fuel injection was at best VERY limited. All has been well to this point.

The other night I get a call at 9:00pm that she is at the gas station and the car won't start. I'll save you folks the immitation over the phone, and just say it turns over at the touch of the key as normal and simply does nothing as far lighting the fire. With a swift call to AAA it was back in our driveway an hour later. The next day I pulled the air filter off and just ran a visual check of all the stuff I could see if anything would jump out at me. The only thing I happened to notice was that the fuel pressure regulator was dribbling out of the atmospheric vent hole, so I figured that's not so good. I borrowed a friends Bosch injection manual and it comfirmed I was right, that's not so good. It's little symptom box matched some of the stuff that had been making itself known the last couple of days, so a part was sourced and ordered. Long story short, at 5:00 am this morning I put it in, turned the key, it turned over happily, no run.

Where in hell do I go from here? I have been told don't dare check for spark by pulling a plug wire and grounding it, so I haven't. How else do I check for spark? I know we here in AZ provided Navjo code talkers to WWII, is that anything like code readers? It has been suggested that the crank posistion sensor is not in a happy mode, but damn stuff is expensive for this car, and I just simply don't want to replace parts until something works... Where do I start?

 

these cars are amazing when they work. but you are right, when something doesn't work it will cost a pretty penny, or well many pretty pennies. there really could be a ton of things that could be wrong. there are so many different computerized parts that narrowing it down could be hard. it could be something as simple as a broken wire somewhere, or it could be something a lot more expensive. it really sounds more like an electrical thing then a mechanical thing. id say check all the fuses first, if not done already, and work your way back. and if you still cant figure it out, you should get someone who can work on Mercedes engines. don't get them to do any maintenance but you can get them to check for the spark. Mercedes are a lot more technical then a classic american muscle car.

 

Thank you Mercedes the Beast! I have already tried the fuses thing. Pulled each one and cleaned 'em, put them back where they belong. I guess what I'm truly asking is there something that is a common problem with these cars that might give me clue where to start. For instance, is there a test that can be run on the crank posistion sensor to check if it's functioning?

I guess when she looked at me the other night and wrinkled her cute little nose and flashed those almond eyes and said "but you can fix anything..." I figured since I'm keeping her and she in turn is keeping the car, I'd better start to "up my game"...

 

the ignition control module is under the plastic cover in front of the brake booster and the crank sensor plug is the big plug with a single wire in it. to test it connect a voltmeter from the center of the plug to ground, the voltage should go up and down.


now what you don't want is it to be the ignition control module. because that is actually big money. but testing the sensor can be done as i stated above. i haven't done it myself but that's what my mechanic has told me can be done.

 

Any chance anyone can clarify that test procedure for the crank posistion sensor? I'm thinking volt ohm meter set up on continuity tester, probe to output, the other to ground and crank the ignition? It would ground and complete the circut as it came around to its mark on the flex plate if it was okay, right?

 

Hi folks,

Chip again - I did a bit of poking about on the internet tonight and found a couple of different ways of testing a crank position sensor. I found the plug for ours on ignition control unit and took a reading with my ohm meter. Testing across the inside of the plug and the outside I come up up with a resistance of 908. I did try turning the car over as I did this and saw a reading that fluctuated in the 1080 range. Am I any where withing spec on this, or is this way out? Some of the internet hits I found on this suggested that it should be right around 380 or so, but none were specific to our car.

I'm beggin' you guys, I HAVE to get this car running again. Have you ever been yelled at in Chinese and "engrish" at the same time? Welcome to my hell....

 

You can still check for spark by using a spark plug, Does your car have a distributor? or do you have coils for each cylinder?
Diagnose if it's a fuel problem or spark.

 

Yes, it does have a distributor. Us old car guys are always told if you touch anything wrong on modern computerized ignitions you let the magic blue smoke out of expensive components, so I get very leery of just checking spark with a grounded plug. If it's okay I'll proceed.

As far as fuel concerns go, I did do pumps, filters and lines in this car two years ago, so I'm pretty confident all is well back there. Also, I mentioned finding the fuel regulator leaking fuel out the atmosperic vent in my first paragraph, and fuel pressure is how I found that mess. Not saying it's an impossibility, (especially with my luck concerning this car!) Just as probable...

 

Few years ago I worked on a no start and a disrtibutor and rotor were burned out.

 

I did pop the cap off the other day and take a look at the cap, rotor and center electrode and all looked a bit worn perhaps but otherwise okay. Nothing obviously wrong there.

 

Well, I thought I would take a couple of minutes and update this thread. I hate to admit it, but I went ahead and took it up to Sam and Mary at Eurocar here in Phoenix. Sam has mentored me a bit through the owner ship of this car, as a matter of fact, helped us find this car. Long story short, it was an ignition module... A couple thousand dollars later and we are back on the road.

But not for long I believe - she has been talking about wanting a '65 or '66 Mustang for awhile now, so I think this might be the right time. I think it might be time to say goodbye to our Little SL via e-bay.
Thanks, Chip Quinn