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  #31  
Old 08-21-2003, 10:21 AM
azhari
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The only values I would be interested in, if I'm trying to evaluate hydraulic control would be various closed loop ranges at various FIXED and STABLE constant load/rpm ranges.

Steve

I will look at the EHA current values again, this time with respect to different fixed/stable constant load/rpm scenarios.

I really appreciate your patience.Please beat this stuff into my head if I'm going in the wrong direction.

Thanks.

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  #32  
Old 09-01-2003, 05:14 AM
azhari
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EHA Current

Steve Brotherton

Apologies for the late update coz I have not been testing the car.

EHA current values as follows :

At idle : 0.25mA (fixed)

Constant load 2000 rpm : -0.25mA

Constant load 3000rpm : -0.25mA

I am boggled!But I hope these values mean something in regards to evaluating this issue.

Just a thought, but with the EHA off and mixture leaned till just driveable, the car still runs rich - black smoke and bad mpg!Does this help in the diagnosis in any way?

Shouldn't I be able to tune the car to run mechanically well without the electronics?

Thanks in advance for your thoughts, Steve.
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  #33  
Old 09-01-2003, 07:39 AM
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This sounds so familiar to my own problem. I just installed all new injectors but obviously have a bad fuel distributor. I'm gonna replace it this week and if it still doesn't run I may yank the entire engine and start over.
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  #34  
Old 09-01-2003, 10:02 AM
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Your readings are more than confusing.

One milliamp equals 0.001A. So, 0.25ma = 0.00025A. Are you sure about the decimal point?

To calibrate you test technique, one must go for one of the fixed readings. Key on, engine off, is usually 20ma (it can be 10 ma or one other value... it is not optional but they did it differently on different models; most are 20ma). The O2 sensor disconnected while running should produce 0.0ma.

Probably the most informative view of whats at stake is the lambda range test. To do the test get the motor idling as best one can with mechanical adjustment with the O2 sensor disconnected. Then take the O2 sensor output lead (the one you disconnected from the sensor - it goes to the controller) and jump it to ground. The controller sees 0.0v O2 output and slowly moves the EHA current to correct. This signal, 0.0v O2 sensor, is interpreted as a lean mixture and after all the capability to correct is finished you should see around 12ma EHA current (plus current gives enrichment).

Now go for the other way. A "D" cell battery would do the trick but it is even easier. Take one hand and contact the O2 sensor output lead we have been working with and place ones other hand on battery voltage (DO NOT hook the sensor lead straight to the battery... go through your body). The small potential making it through your body will fool the controller into thinking it is seeing hi O2 sensor output voltage and it will lean out the mixture by going negative 12ma EHA current.

From these basics you may see my problem with your figures. First .25ma is inconsequential. The 0.0ma I give for the open loop (disconnected O2 sensor) is likely to be more than .25ma off of zero just due to meter calibration or even controller variables. It never controls at that level. This could mean you are really reading 0.0ma all along. The difference between +0.25ma and -0.25ma is inconsequential. The controller would see it as zero.

If you are off one decimal point you are twice the values I give for max readings in either direction. A very likely senario could have 12ma at idle and -12ma at both other rpm ranges. Such a group of readings would be characteristic of a vacuum leak. It would take full mixture correction at idle but that correction would leave it too rich at the higher rpm where the leak is small in proportion, thus the minus readings off idle.
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Continental Imports
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33 years MB technician
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  #35  
Old 09-01-2003, 12:08 PM
azhari
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Confusing EHA current...

Steve

Believe me, I have read other posts with regards to EHA current and I cannot understand the readings I am getting.

As far as the decimal point is concerned, I'm pretty sure it's in the right range coz I'm using an analog ammeter with the dial-type setting.

Set at 250mA and 25mA produced very slight (almost zero) readings.Only when I set it at 2.5mA full scale deflection, then I could see the reading at idle/acceleration.

At accelleration, the needle swung negative so I switched the terminals to see the reading and I got 0.25mA - at both constant rpms.

I may have screwed myself on the scales so I'll scrutinise it once more.

But if the readings are correct, it would mean that the readings are actually zero all the way!

So far I have run the car with the EHA on and off - but the O2 sensor still connected.The only reason I have not done the O2 test is that I have frustrated myself looking for the connector.It doesn't seem to be anywhere under the passenger side or the driver side carpet.If someone has a photo showing where it's at on their 190e, it would be very helpful.

It doesn't help that mine is a 1991 190e 1.8 Euro RHD so some of the stuff in my car may be different from the US cars.

Steve, by disconnecting the EHA, the O2 sensor is also out of the equation isn't it?So if it's faulty, with the EHA off, I should still be able to adjust mixture to run mechanically well - but I can't.

Not being able to find my O2 sensor connector is really a bugger coz I am unable to check if it's working - if i could verify it's OK, I could try to get the car in closed loop.

Quote:
If you are off one decimal point you are twice the values I give for max readings in either direction. A very likely senario could have 12ma at idle and -12ma at both other rpm ranges. Such a group of readings would be characteristic of a vacuum leak. It would take full mixture correction at idle but that correction would leave it too rich at the higher rpm where the leak is small in proportion, thus the minus readings off idle.
I found this information really interesting.It also makes perfect sense.But would a vac leak screw my mixture adjustment efforts with the EHA off?It would seem to me that the engine is getting some kind of "false air" so it is dumping fuel to compensate.

Although frustrating at times, this has been a sensational learning experience for me coz along the way, I have learned to test/check various sensors/switches/etc of the KE-Jetronic system.Cool!

Steve, sorry for the long post and the seemingly vague questions tossed in every paragraph or so.

I thank you for your patience.

Cheers.
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  #36  
Old 09-01-2003, 12:11 PM
azhari
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Ooops...One more question...

Steve

If it is a vac leak, are there specific areas that would cause rich running - or can a vac leak ANYWHERE in the engine contribute to the problem?
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  #37  
Old 09-01-2003, 12:37 PM
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OK, forget electronic correction.

With the EHA disconnected, what is your problem? Can you adjust the mixture to a good idle? Can you go to far rich and make it run bad? Can you go lean and make it run bad? Is there a better point in the middle?

If you had a vacuum leak and you did the above mixture movements, there would be a point where you corrected by going richer and overcame the extra air. If you did that mecahnically and you had an air leak you now would be running much higher rpm than idle should be.

Remember that air is what control rpms, not fuel. The highest rpm for any amount of air going in will be the amount of fuel that gives the best mixture.

You are right that you must solve your mechanical fuel problem before worrying about the electronics. The KE system does just fine warm without electronic control. BTW, are you sure you have an O2 sensor. Many euro models of KE didn't have catalytic converters. Only cars with TWC (three way cats) had O2 sensors.

Look at your exhaust if in doubt. The sensor will be obvious in the exhaust if it is there.
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  #38  
Old 09-02-2003, 12:18 AM
azhari
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Thanks for the prompt response, Steve.

I am now running the car without the EHA on.

I have leaned the mixture (counterclockwise) in order to get driveability.

Before, it was bogging down on accelleration and smoking really bad.

Now,having leaned the mixture, although it is still smoking (albeit less than before), the car is driveable without the a/c on.

Idle is stable around 750 when cold but once warm, idle surges up and down between 550 and 750rpm.When stationary, feels like car wants to quit (and sometimes it does at decel).

Accelleration and driving at speeds is not a problem.But still smoking while driving.At idle, exhaust smell is strong.

So the car is running rich even with the mixture leaned.

If I richen the mixture, I can get a steady idle but the car will severely hesitate off the line (even with a/c off) and while driving, it will smoke bad and power is low.Feels like it is flooding.

This is the reason why I have leaned the mixture.Having done so, the car still smokes and gas mileage is bad (slightly better than before I leaned it).Car now consumes 44 litres having run 300km.Before I leaned the mixt, it could only do 260km per 44 litres.

So it doesn't look like a vac leak does it?From your information, I deduce that if it were a vac leak the car would run lean to begin with and that I should richen the mixture to compensate - but the opposite is true in this case.

Also, car starts without accellerator in the morning (although EHA off so no cold start) 1st try and when warm needs the accellerator to start before it catches.

I have also verified the OVP (just in case) by doing the EHA key-on value - it is 10ma with both of my OVPs (I have a good spare).

One more tip for the problem - when I got the fuel pressure regulator replaced (old one was leaking) with a used one, I got a mech friend to help retune the engine with EHA on (he richened the mixture bi tby bit and revved the engine every now and then producing billowing clouds of black smoke).By the time he finished (he richened the mixture), there was hardly any black smoke when revving.

He also turned the a/c on and tuned the car so there would not be a flat spot when accellerating.

After he finished, the car drove really well for about 15 minutes like new.

Then, it went back to feeling like it was flooding - bogging down while driving, severe hesitation and smoking (worse with a/c on).

That's when I disconnected the EHA (again) and leaned the mixture.

Could it be that the used regulator has gone south?

I am not sure how the fuel distr works but it seems to me that the regulator maintains the control pressure on the upper chamber and if it does not work right, it's like more fuel but less air - so rich running even though mixture leaned?

I'm not sure.

Please advise.

May thanks, again.
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  #39  
Old 09-02-2003, 02:30 AM
azhari
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Steve

Quote:
If you had a vacuum leak and you did the above mixture movements, there would be a point where you corrected by going richer and overcame the extra air. If you did that mecahnically and you had an air leak you now would be running much higher rpm than idle should be.
I missed this paragraph.

I guess I don't have a vac leak or my car would run lean.
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  #40  
Old 09-02-2003, 07:48 AM
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Let me try and point something out.

Your car should run real good over a wide range of mixtures. It won't do that if running in closed loop, but you have the EHA disconnected so you are obviously in open loop. (that just means there is no more electric control).

If I were adjusting the mixture the car would feel the same from about a mixture of .8% CO to around 5% CO. This is a huge range. If you set it to 1.5% CO (which would be about where cars were before closed loop control) it should easily stay there indefinitely. IF THAT is not the case there are other factors at work that we have not been discussing.

Basics of engine diagnostics need to be reviewed and don't leave out ignition. Before I would ever be this deep into fuel control I wouldhave watched all the phases with my ignition scope.
Attached Thumbnails
190e running rich with eha on/off.Bad mpg.Help!-vw-3cyl.jpg  
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Continental Imports
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33 years MB technician
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  #41  
Old 09-02-2003, 07:52 AM
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Or I dare you to figure this one out. Pay attention to the units of measure. Car is a 88 300SE
Attached Thumbnails
190e running rich with eha on/off.Bad mpg.Help!-bad_vac_-6_misfire_rocker_hsg_off.jpg  
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Continental Imports
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Bosch Master, ASE Master, L1
33 years MB technician
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  #42  
Old 09-02-2003, 09:02 AM
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Or like this:
Attached Thumbnails
190e running rich with eha on/off.Bad mpg.Help!-vw-3cylsuper.jpg  
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Steve Brotherton
Continental Imports
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Bosch Master, ASE Master, L1
33 years MB technician
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  #43  
Old 09-15-2003, 04:06 AM
azhari
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Stevebfl

I am back with some time to work on the car (had REAL WORK issues to settle).

Looking back at my 15 minutes of joy when I replaced the fuel pressure regulator with a used one, I am thinking that the used one has a stuck diaphragm causing excessive high fuel pressures (hence super rich condition).

I still have the EHA off, but car starts without accelerator/1st try in the morning!

When warm, needs the accelerator while cranking to get the engine to catch.

When cold, idle is steady and car is very responsive.Still smokes lightly.

When warm, car feels reluctant to accelerate (surging).And if I step hard on the accelerator, smokes REALLY bad and struggles to accelerate.On inclines, it struggles badly if the current speed is low.

Does the basic operation of the fuel pressure regulator vary with temperature?As I have the EHA off, all sensors are bypassed so I doubt if this has any corellation to my problem.

The techs here wanna go straight to a fuel distributor replacement without any diagnostics, which pisses me off (in principle and also because the FD is a very expensive component).

I will be getting my hands on the 190e workshop CD soon and I hope to get more help from it.

I appreciate your patience, Steve.

Meanwhile, I am stumpped...
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  #44  
Old 09-15-2003, 06:13 AM
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your 190E problems

Whats really wrong with your Benz mate? I can't work out whats wrong with it as I am not so Benz educated. Sad to say if anything went wrong with my C180, off it goes to my fav. indie almost 50kms away who can find anything wrong with it and fix it by the next day or two. Charges less than the stealer, but not as cheap as some pretend indies who only want a share of the $$$ they think is out there.

Please read my last emails and get back to me soon, will you?
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  #45  
Old 09-15-2003, 07:14 AM
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Hi azhari,

I am also trying to solve these kind of erratic problems. And have installed DIY harnesses for chekcing the relais fuelpump, OVR and switch to set offline the EHA

From what I have read on the principles of these distributors, there is a O-ring gasket on the underpart of the Distributor, on the cylider that commands the fuel flow to the fuel lines and that prevents fuel to enter the air flow. If that leaks fuel enters directly through air intake and mixture always too rich.

Have you taken away the fuel distributor? Would you have any photo ( or drawing from user manaul) of the bottom part of the fuel distributor?

In a previous post you said having measured the fuel pressure , could you tell me how you did it,
Have you done that measurement while driving?.

In advance many thanks, and goodluck.

mine is a 260E, 1988, 370 000km


Last edited by cc260E; 09-15-2003 at 07:52 AM.
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