Thanks Steve!

I will pass this on -- I've suspected a sensor or wiring problem, too as the ignition timing is calculated. Very hard for it to be a mechanical failure other than incorrect resistance, etc.

Could the coding plug be bad?

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I have never seen one bad. They are only resistors. It could be posible to tamper with one though.

If the timing is right cold, I would really worry about the temp sensor. Otherwise I might worry about the ignition controller.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Ignition contoller is new, so I will have Hans take a look at the temp sensor.

These can be a pain -- I've seen some on other cars (volvo) and are physically identical, but internally different, so they won't work when installed -- my sister's 92 Volvo 740 Turbo was like this -- severely overheated when the head gasket blew/radiator failed (don't know the sequence, it was fried when I got there). Temp sensors and thermostat bad, so I snagged one from a junkyard as I didn't have time to get one from the dealer. No go, the proper one had two resistors connected to the body, all the others Volvo used had a single resistor connected across the two wires. Needless to say, the check engine light stayed on a lot until we got the correct one in.

Thanks again!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Well this question won't help any but I am curious, with four pulses per rev how does it know where 0 is? I guess it doesn't care about 0 just needs to know a relative position for timing and the distributor gets the spark to the right place. If it is sensing metal tabs then that would be a VRM type, a coil of wire wrapped around a magnet. The oldest schematic I have is from a 97 C series and it shows the same thing for the CKP sensor which I believe means CranK Position. It shows and inductive (VRM) type sensor that sends its signal through a shielded wire to the engine computer. These sensors are pretty bullet proof usually. They put out a little sine wave pulse as the metal thing flies by. They are often used to sense teeth on a gear. Same kind used for wheel speed measuring. Hard to believe it is bad. Bent tabs probably wouldn't cause 20 degrees of error. I think stevebfl is on to something with the temp, vacuum, coding plug. I am guessing the computer is following instructions but getting bad info. Same trouble Bush is having with his war.

Mike

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

You got me. However, the computer doesn't need to "know", only to fire the coil at the correct delay -- the distributor sends the spark to the correct plug.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Does the distributor have 2 vacuum lines? I seem to remember some models had a vacuum retard (a lot!) that came on just off idle to improve emissions, then went off at idle, and off again when engine speed went up above ?1000rpm? and then vac advance kicked in like normal. It was a ***** for performance and economy but reduced NOX and hydrocarbons without a cat.

Alas, timing is determined electronically on the 560, the dizzy just gets the spark to the correct cylinder. Coil is fired by the engine computer via the switching unit (aka ignition computer).

If it was that easy, I suspect the PO wouldn't have pulled the K-jetronic ignition off and put a Holley carb on it....

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Hey guys I have a problem kinda like yours.. I have replaced the whole fuel dist asembly and the car ran great for about 10 mins.. then went into limp mode.. and has no started since.. It started with a slite miss and was drivable.. and all of sundden would not go more than 10 mi an hour.. replace ovp eha and all elect and fuel distributor.. plugs/wires/caps and rotors oil.. what would stop a car.. I do have a leak from the power steering box that blows back could this be causing the cranks position sensor to fault.. dont think so but Im grasping Im on the verge of throwing my hands up...
D

You need to do some diagnosis to find out why it won't run -- check for fuel pressure, fuel delivery, spark, spark timing, etc.

No way to fix it until you know why it won't start....!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

First I do not appreaciate the demeaning tone of your reply.. You assumed that I had not done or had done any work to the car.. My local tech did chk fuel pressure delivery checked thfuel for rust(found none) replaced the fuel filter.. checked the timing best he could..(I live in Bartlesville, OK 10 mi south of Kansas) so technical expertise is hard to come by.. replaced plugs wires cap and rotor.. checked the fuel pressure regulator was good.. states that the coolant temp sensor "seems" to be good as he is getting voltage to the cold start valve.. the idle was pretty bad but cleaned the idle control valve and it improved.. tech states all voltages appear to be correct.. the reason I asked the open ended question is that I wanted as much feed back as possible even if the feedback suggested things I/the tech had already tried.. the thing is it will eventually start and run great for a short while but go into limp mode shortly there after..usually after the time it takes to warm up.. so Im thinking o2 sensor or any other sensor.. the engine gets spark and fuel just intermittantly so suspect what ever is cause this intermittant running problem is why it wont start as well..you see I have done tons of trouble shooting for approx 5 month countless hours from me and 3 garages.. here in town...

If you have test data then spell it out. Saying that you have tested this and that is of no use to a real tech. I tend to ignore posts with no specific question and no test results. Good luck.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

I am sorry I was no try to pawn myself as a "real" tech I was only trying to hopefully save someone some time and trouble shooting..In a "thats interesting my car is doing something like that too" kinda way Im sorry if my post came across any other way..I am wholly certain that you have more skill than myself and again was not trying to come across as "real" tech.. I am very aware of my limits in time and skill as a tech and is why I have an actual tech(s) take a look at the car.. I was also a trying to save the site the entire saga of the ordeal.

Just like going to the doctor, you really have to do a complete diagnosis to fix the problem. I'm not being demeaning, just stating a fact.

If you have no spark, you must determine why the ignition isn't working at that particular time before you try to fix it, else you tend to spend rather large sums of money and still have the problem. These cars will cost you a fortune that way.

Yes, your problem does sound similar, and Hans has ordered the pickup to replace it (temp sensors are already new). However, in your case I suspect the mixture is going way lean in closed loop -- but I don't know that, it must be tested (via EHA current or via the duty cycle). If the O2 sensor is bad, this is likely, but there are more things to go wrong that that. Vacuum leaks come to mind -- injector seals, manifold half seals, the boot between the throttle body and air flow meter, the boot between throttle body and manifold, door locks, idle control valve hoses, vacuum controls. Any air not going through the air flow meter will throw the mixture off.

Bad fuel distributors are a common problem, and depending on the source of a "new" one (rebuilt, I'm sure unless you have DEEP pockets!) can be worse than the one you traded in. Stick with a warrented Bosch rebuild, some of the other sources send you distributors that don't work properly.

Next step for you is probably to find out what the fuel mixture and timing actually are -- if the tech can only measure "as best as possible" I (and probably no one else here) can do you much good unless we know why he couldn't do better -- ignition timing can be read directly from the diagnostics computer if he has one.

Intermittant spark is a real problem -- could be several things, some rather expensive, and you really need the computer diagnostics to tell, other than a flaky ignition switch.

I'd personally start with the O2 sensor signal and diagnostics, then mixture, then ignition unless the spark goes away, in which case you must determine the problem there first! Hard to diagnose anything else if it has no spark.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Im quite familiar with the need for stating facts.. in fact I am paid to inspect potential MB purchases for individuals of wich all are running strong to date.. this is my second mercedes the first being an '82 300 sdl that I sold at a profit with 245k mi so I am familiar with the cost of repair and components..I have not tested the vaccuum leak scenario only because I can hear no hisses or see any bubbles of fluid and the door locks all seem to work.. the hose seem to be decently flexible for a 13 y/o car...also I have not tested the autoleveling system for leaks the spark issue has been solved.. the bolts connecting were tightend.. the fuel distributor works great.. I bought it used from my trusted parts guy for years..the tech states that it does not leak a drop..no fuel leaks of any type.. the next step is to take to my guy in Tulsa here.. for a complete DX on his pc to eliminate any more guess work.. This was my intention from the begining but the "gentleman" I purchased the car from wanted to try to fix it locally first..I was thinking of getting rid of the car only because I dont have time to follow up with techs and keep a journal..the diesel was never this much trouble.. the money was never an issue.. and I apologize if it seemed I was trying to get advice with out giving in return. Ill keep you all updated on the results..
D

Chiming in with a wild guess based on a quick look at the manual diagrams for this model...(I assume it is an 86)

There is a temp sensor, an EZL control unit, and a throttle position sensor in the system that all work together to advance and retard the timing in response to their various signal inputs. If you are certain the temp sensor is OK then I believe the throttle position sensor may lie at the root of your trouble. The temp sensor appears to advance the timing ,via vacuum, relative to temps above 95 degrees C, and the control unit appears to be controling things by moving the timing in response to temp and vacuum signals, so I think the throttle position sensor should be checked. Why?

It senses whether there is an idle position or throttle opened position. At idle the specified timing is between 3 & 7 degrees, and at throttle open the timing is between 24 and 28 degrees, the difference between these values being 21 degrees. These timing values are w/o vacuum but the difference in timing is the same when vacuum is present. I believe your throttle position sensor may be going out and incorrectly signaling the unit to advance the timing 21 degrees then retard it 21 degrees. It may be signaling the EZL to advance timing 21 degrees at idle and then signaling to retard it 21 degrees at throttle open.

If the throttle position sensor checks OK then I'd look at the EZL unit to see if it is mixing up signals or intermittently failing. The car may have been timed with the EZL unit having wrongly advanced the timing signal 21 degrees then it kicks out and the basic timing is then 21 degrees retarded.

I suspect one of these two units, and believe you should check the TP sensor first.

Might be worth looking into... just a thought.

Good hunting,

230/8