Ezl ignition and td-signal - help needed - PeachParts Mercedes-Benz Forum

190dee · #1 06-04-2003, 11:20 AM

Hi to everyone dropping in on this thread,

The car involved is 1987 190E 2,3 8 valve (M102), ezl unit, auto tranny

Let's get to the problem itself. My car stumbles, engine dies for milliseconds randomly. As engine stumbles, the rpm-gauge drops. The engine doesn't stall but it "stumbles". It's not a certain rpm reading, it can occur all over the "scale".

I have checked all the ignition cables, rotor and distributor cab (changed to new ones) and run on bosch iridium spark plug. Plugs looks good.

I have been monitoring this problem for some time so this is what I know;

I measured the L5-sensor located next to power steering pump, it's within specs on service manual. No ground leaks to ground. I tried to follow the coax cable and wiggle it when measuring but no difference. I do not have a scope to see the shape of the pulse it generates.

I did also check the cable labeled td-signal from ezl unit to terminal block on diagnose connector and from connector to fuelpump relay/cis-module. With a ohmmeter hooked on the the cable I get no resistance. But when with cables plugged to units and ohmmeter on ground and terminal block at diagnose connector I get 960 ohm. I narrow down the cable with connection to ground to fuel relay/cis unit cable. Is this right? Should there be a leak down to ground? The reading was measured with battery unhooked.

I did also read that ignition modules are usually working or not so I hope mine is still ok. Am I wrong? Could it cause random failures?

I take the dropping rpm-gauge as a hint of what's going on. Tacho is connected at the terminal block on diagnose connector. What could cause the missing td-signal?

190dee · #2 06-15-2003, 12:28 PM

Bump!

stevebfl · #3 06-15-2003, 12:48 PM

Intermittants are the worst of problems.

You state L5. Sitting at home this doesn't mean much to me and I can't remember what is the ignition trigger on your car. I can tell you it is not on the front of the motor unless its inside the distributor.

It is either an armature like inductor inside the distributor or a crank sensor on the flywheel. The sensor on the balancer was for an engine analyser that never made it to the US. It tracks timing and isn't part of engine controls.

Looking at any of these devices with an ohm meter is not likely to find an intermittant. The signal needs to be monitored with a scope to tell whether the event is a result or the cause. RPMs logically drop when the engine stumbles or dies. I would probably use two channels and watch ignition primary on one and the engine speed signal on the other. I drive the car in snap shot mode and trigger it when the event occurs. This is adjustable but normally leaves me with a 30 second snap shot that starts 15 seconds before I trip it capturing the event for multiple reviews.

Even with proper tooling testing can be inconclusive on intermittants. This often becomes the worse source of customer irritation. They believe (I don't know why) that we should be able to test it. Well if it ain't broke it won't look broke; most times.

As much as I hate to say it, substitution is sometimes the only effective choice.

190dee · #4 06-15-2003, 01:17 PM

L5 is the same as crank position sensor.

I haven't removed it for futher look yet but maybe it would be a good idea to give it a good visible checkup.

I do not have a scope but I guess maybe I could find one to borrow or rent.

So with that setup I would verify if it's a missing signal from cps-sensor or if the ezl-unit itself is faulty, right?

Could a bad coil cause this? Since the rpm gauge drops for milliseconds I have so far excluded this but I have no facts verify it.

stevebfl · #5 06-15-2003, 01:36 PM

If your ignition wiring diagram shows a L5 crank sensor then it is on the flywheel/bellhousing.

tHe point of watching on a scope is to see which signal stops first or together. The primary ignition is controlled by the EZL module as a reflection of the engine speed signal recieved from L5. So if the L5 signal dies the primary dies with it. But if primary dies there is no reason for the L5 signal to die till the motor is totally stopped.

There are many secondary ignition failures that can cause the fault you describe. Many could be seen without symptoms with an ignition scope. Low available voltage, high resistance paths to ground, etc. can be seen with proper technique.

190dee · #6 06-15-2003, 01:45 PM

Yes, I already thought about voltage supply and grounding points. I have cleaned connections and changed bad ground wires.

As far as the voltage goes; I did remove the regulator and visually inspected coals. They do look good to me. I have monitored system voltage and it's stable.

The alternator itself has never been changed and I have got about 216 000 km on the odometer.

stevebfl · #7 06-15-2003, 01:57 PM

The sentence "Low available voltage, high resistance paths to ground" has nothing to do with "I already thought about voltage supply and grounding points. I have cleaned connections and changed bad ground wires."

I am refering to secondary ignition. High resistance paths to ground carry spark voltages to ground instead of to the cylinder. This is intermittant as the resistance would be such that as long as the voltage stays below a level the spark goes where it is supposed to. As the voltage requirement goes up the path becomes the lowest voltage path, taking out that cylinder or all cylinders if the path is from the rotor or coil wire.

A low available voltage means that (for example) a coil only puts out 15kv (should be 30kv or more available). At idle cold the engine might only need 10kv to fire the rich mixture of warm-up, but when warm as the required voltage hits 15kv the fire goes out.

190dee · #8 06-16-2003, 01:33 AM

Yes, now I see. So a good advice would be to bring this coil in for diagnose (output, resistance aso.). As this is a random failure I understand it doesn't need to show but a faulty one would be one step in the right direction.

Thanks for all the replies. I will post back as this "project" continues.

vuppal · #9 06-20-2005, 10:00 PM

mercedes/92/sl500 check engine light came on and car is in no start condiiton How i can tell my Ezl switch good or bad

vuppal · #10 06-20-2005, 10:31 PM

Hi everyone I need your help mercedes/92/sl500 my car chech engine light came on and now car is in no start condition.i already changed camshaft sensor.didn't help How can i tell my Ezl or frywheel Sensor bad.Thk

autozen · #11 06-21-2005, 10:57 AM

I agree with Steve about intermittents being a PITA and car owners not understanding why you can't find the problem. I had a 90 300SEL drive me crazy with intermittent stalling and not starting. It never stalled for me. I was down to swapping parts. Iwould put a part in and the car ran fine for a couple of weeks, and then I'd get the call that the car was dead again. I finally hit it with an EZL module. I had a 500SEC with intermittent run and stumbling. A new coil took care of that problem. I had a 560SL die and restart. I could let it set and idle for hours. I got lucky on that one. I was monitoring fuel pressure and saw primary pressure drop off. Fuel pumps solved that one. I would look at those components. I've never replaced a crank position sensor. I'm sure parts houses sell alot of them to be installed on cars that have been mis diagnosed.

Good luck,
Peter

fsd34760 · #12 02-23-2006, 02:06 PM

hi,

I HAVE AN 1989 MB 190E WITH A 2.6 LTR ENGINE.

PROBLEM
CAR WONT START

PREVIOUS ISSUES WITH CAR
NONE RELATED TO THIS

MECH DIAGNOSIS
BAD IGNITION CONTROL MODULE

SUGGESTS REPLACING $1900 PART

I SAY NAY NAY

WHERE CAN I HAVE SOMEONE DIAGNOSE SUSPECTED FAULTY UNIT

THANK YOU IN ADVANCE

Quote:

Originally Posted by stevebfl

Intermittants are the worst of problems.

You state L5. Sitting at home this doesn't mean much to me and I can't remember what is the ignition trigger on your car. I can tell you it is not on the front of the motor unless its inside the distributor.

It is either an armature like inductor inside the distributor or a crank sensor on the flywheel. The sensor on the balancer was for an engine analyser that never made it to the US. It tracks timing and isn't part of engine controls.

Looking at any of these devices with an ohm meter is not likely to find an intermittant. The signal needs to be monitored with a scope to tell whether the event is a result or the cause. RPMs logically drop when the engine stumbles or dies. I would probably use two channels and watch ignition primary on one and the engine speed signal on the other. I drive the car in snap shot mode and trigger it when the event occurs. This is adjustable but normally leaves me with a 30 second snap shot that starts 15 seconds before I trip it capturing the event for multiple reviews.

Even with proper tooling testing can be inconclusive on intermittants. This often becomes the worse source of customer irritation. They believe (I don't know why) that we should be able to test it. Well if it ain't broke it won't look broke; most times.

As much as I hate to say it, substitution is sometimes the only effective choice.

mctwin2kman · #13 02-23-2006, 03:28 PM

190dee

I notice you said Iridium Plugs! Are those resistor type plugs?

These cars have 1KOm resistance built into the cap, rotor and plug end caps. Thus you need to use non-resistor plugs or you will have a weak spark due to more resistance. Bosch Copper are what go on these engines in these cars, no platinum or irridium plug will work correctly. They will at first but not after a few miles.

I would also check for vacuum leaks of any kind and clean the IACV with liberal amounts of carb cleaner. As well as the AFM area. Would not hurt to run a few tanks of gas with fuel injector cleaner either.

Search the board and you will find many many threads about using non Copper Resistor type plugs on these engines. You will find that you get the same issues you are having.