KE-Jetronic/CIS-E Troubles with my ECE 190E 2.3-16

[mkodama]

I've come across a lot of good info searching this forum, but I am still stuck with my fuel system problems, or at least, I think they are fuel system problems.

The problem is that when I accelerate, the engine bogs down, runs lean and misfires. The car starts up quickly and idles great otherwise.

-I have tried adjusting the "tower" on the fuel distributor for both leaner and richer, with no help.
-I paranoid of vacuum leaks so I took apart the entire intake and replaced everything rubber and all gaskets, and the engine performs identical to before, so I know it is not vacuum leak related.
-Also, this car is a 1985 ECE region car, so there the car has no factory oxygen sensor, the CIS-E controller has no input for one, and there is no terminal for giving duty cycle at the little round diagnostics port. I do have an aftermarket oxygen sensor installed on the cylinder 2 exhaust manifold runner in place of a dummy O2 sensor that was on the car when I got it.

I would love to get this engine running so any help would be appreciated. Thanks for your time.

[intrepid1981]

I had the same type of symptoms on my 300CE. I adjusted the EHA and it's now MUCH improved.

To do this, you remove the EHA from the side of the fuel distributor.

Then there is a small adjuster screw on the back of it. Turning clockwise richens the mixture and counter-clockwise leans it out.

I had to turn my one a quarter of a turn CW to richen it up and the car runs really well now; no more hesitation when cold...

[mkodama]

Originally Posted by intrepid1981

I had the same type of symptoms on my 300CE. I adjusted the EHA and it's now MUCH improved.

To do this, you remove the EHA from the side of the fuel distributor.

Then there is a small adjuster screw on the back of it. Turning clockwise richens the mixture and counter-clockwise leans it out.

I had to turn my one a quarter of a turn CW to richen it up and the car runs really well now; no more hesitation when cold...

I will give this a try when I have the time in the next few days. I very much think the problems are coming from the EHA, since it is what adjusts for acceleration enrichment, which it seems my car is lacking.

I'm curious why it would go out of spec though, and I wonder if there is something clogging it?

[mkodama]

I've been doing more diagnostics and I just keeping getting more and more confused. Part of the reason being that this is a 1985 model year, grey market car, so the wiring is quite a bit different from the later US spec cars, which I'm looking at the manuals for.

I've been holding off on adjusting the EHA because looking at the drawings and operation of it, it really shouldn't need any adjustment, and I think Mercedes-Benz doesn't think so either with their marking paint over the screw heads. So I'm going to hold off on that until I can really prove that is the issue.

One thing that definitely seems off is that the air flow meter position sensor is not getting the 5 volts it is supposed to be getting. This sensor is directly related to acceleration enrichment, so I'm going to look into this more.

[Ramblin]

Had similar problems with an early Datsun 280Z which had a similar system with no O2 sensor and it would bog down on acceleration. It turned out to be the air flow meter potentiometer that was feeding the wrong signal back to the very basic computer for which there was no adjustment. After replacement of the whole device it then was very fast with no hesitation at all.

[hstuehmeyer2000]

I suggest(if possible) that you build a code reader and see if the engine computer reports any problems.

http://www.benzworld.org/forums/w124-e-ce-d-td-class/1229198-code-reader-2.html

[mkodama]

Originally Posted by Ramblin

Had similar problems with an early Datsun 280Z which had a similar system with no O2 sensor and it would bog down on acceleration. It turned out to be the air flow meter potentiometer that was feeding the wrong signal back to the very basic computer for which there was no adjustment. After replacement of the whole device it then was very fast with no hesitation at all.

Thanks! That's good to hear that this single item may be the root of all the problems.

[mkodama]

Originally Posted by hstuehmeyer2000

I suggest(if possible) that you build a code reader and see if the engine computer reports any problems.

http://www.benzworld.org/forums/w124-e-ce-d-td-class/1229198-code-reader-2.html

I'll look into it more, but I'm pretty sure my car has no diagnostics capabilities. Definitely no O2 and codes at the place a US 190E would normally have them...

[Edward Wyatt]

With CIS, the first step in diagnosing a running problem is a fuel pressure test.

Most people don't have fuel pressure gauges, so let's look at the situation.

First, I wouldn't go messing with the EHA, I worked on these cars when they were still new and we never touched it.

Second, make sure the secondary ignition system is in good shape before doing anything else. Pay particular attention to the rotor button, and check the ohm resistance of the plug wires against specs. Some aftermarket sparkplugs are notorious for causing running problems, and I would make sure you have a good set of plain old copper core spark plugs. NGK makes an excellent copper core spark plug, just make sure you avoid any fancy platinum tipped aftermarket junk.

I would, at the very least, set a baseline and throw a new set of copper core plugs in it first.


Third, when adjusting the mixture at the fuel distributer always remove the 3mm allen key between adjusments and realize the a tiny movement goes a long way so to speak. This adjusts fuel mixture across the board, more than half a turn indicates a more serious issue that needs to be addressed before the mixture can be set. Faulty secondary ignition comes to mind. Counter clockwise movement leans out the mixture, and clockwise movement richens the mixture.

I would at least use a vacuum gauge and try to set the mixture for the highest reading if you don't have access to a CO meter.



The fact that it starts and idles ok makes me think the problem might be ignition related. Or a plugged cat, if it has one. A vacuum gauge will point you in the right direction.

[mkodama]

Originally Posted by Edward Wyatt

With CIS, the first step in diagnosing a running problem is a fuel pressure test.

Most people don't have fuel pressure gauges, so let's look at the situation.I bought a fuel pressure test kit specifically to help with this car, and input pressure is 5.8 bar. Until not long ago I didn't know where to check lower chamber pressure, so I will get that when I get a chance.

First, I wouldn't go messing with the EHA, I worked on these cars when they were still new and we never touched it. Agreed

Second, make sure the secondary ignition system is in good shape before doing anything else. Pay particular attention to the rotor button, and check the ohm resistance of the plug wires against specs. Some aftermarket sparkplugs are notorious for causing running problems, and I would make sure you have a good set of plain old copper core spark plugs. NGK makes an excellent copper core spark plug, just make sure you avoid any fancy platinum tipped aftermarket junk.

I would, at the very least, set a baseline and throw a new set of copper core plugs in it first. Currently there are some Bosch +4 platinums, which I doubt are very good, but I also would't think they could make the car run as bad as it is right now. If they really were a huge issue, I could switch to a set of resistor-less NGK plugs I have. Also by the fact that when the car was running, if I pushed on the air meter at the same time I pulled the throttle linkage, I could get the engine to respond quite quickly and without bogging. I'm very convinced the ignition system isn't causing any "big enough" issues at the moment.


Third, when adjusting the mixture at the fuel distributer always remove the 3mm allen key between adjusments and realize the a tiny movement goes a long way so to speak. This adjusts fuel mixture across the board, more than half a turn indicates a more serious issue that needs to be addressed before the mixture can be set. Faulty secondary ignition comes to mind. Counter clockwise movement leans out the mixture, and clockwise movement richens the mixture.

I would at least use a vacuum gauge and try to set the mixture for the highest reading if you don't have access to a CO meter.



The fact that it starts and idles ok makes me think the problem might be ignition related. Or a plugged cat, if it has one. A vacuum gauge will point you in the right direction.Actually, as of the other day when I tried to do some more diagnostics, the car doesn't start up anymore. I'm baffled as to what I've even changed since last time.

Thanks for the excellent response. Definitely some stuff I can look into.

[ps2cho]

when I got my 260E it would bog down on bottom end acceleration then suddenly clear up at around 3000rpm and run really good.

I swapped the EHA with a spare I had and it no longer bogged down. I think you are experiencing the same issue.

[mkodama]

I've gone through the service manual troubleshooting and this is what I've got so far.

Testing over voltage protection relay
-Terminal 1 of ECU connector has battery voltage. OK
End of Test.

Testing Coolant Temperature Sensor
-Coolant temperature sensor values are correct. OK
-Read current value going to EHA. NOT OK
-Test resistance of EHA. OK
-Test continuity from coolant temperature sensor to ECU. OK
-Test continuity from EHA to ECU. OK
End of Test.

Testing Acceleration Enrichment and Airflow Position Sensor
-Read EHA current value at idle and under quick acceleration. NOT OK
-Read voltage between terminals 1 and 2 and between terminals 1 and 3. NOT OK
-Read voltage while deflecting airflow plate. NOT OK
-Test wires between ECU and airflow position sensor. OK
-Test RPM signal. (didn't get around to this)
-Test continuity between EHA and ECU. OK
End of Test

Testing Throttle Valve Switch
-Check resistance of switch at idle and full throttle. OK
End of Test

Primary Fuel Pressure: 5.8 bar OK
Lower chamber pressure at idle at 80°C: ?
Lower chamber pressure at idle at 20°C: ?
Lower chamber pressure at acceleration at 20°C: ?

Notes:
-My fuel pressure test kit is not able to reach the lower chamber port.
-I am not getting 5 volts to the airflow position sensor, but signal and ground are present and working.

[mkodama]

Does anybody have a wiring diagram for the 1984/1985 standard 2.3-16, know anything about where the air flow meter position sensor gets its 5 volt source, or what reference resistor R17/1 is?

[mkodama]

Well, the fuse in the over-voltage protection relay was loose, so I fixed that and now I have power going to the airflow position sensor and EHA again. No difference in running condition.

The EHA and airflow meter position sensor both have 7.92 volts going to them. In the US 2.3-16 the airflow position sensor is supposed to get 5 volts. Is the 8 volts my airflow meter position sensor getting normal or not for a european car?