190e running rich with eha on/off.Bad mpg.Help!
 

My 190e used to get about 420km before the fuel light came on.

Gradually, fuel mileage became worse over a couple of weeks.

Now, I'm down to 260km per tank with the fuel light on!

Car runs rich and is smoking - especially bad on acceleration.

Also, severe hesitation from stop.

The only thing that is good is that I don't have problems with cold/hot starts - turn key once without pressing accel pedal.Also, the idle is smooth - have never had any idling problems.

I have run the car with the EHA off (so I should be able to mechanically adjust to the correct mixture) but it is no different - still running rich and I lose cold start capabilities with the EHA off.But sometimes (very rarely), I noticed that with the EHA off I can turn the engine over with the 1st key-on w/o accel pedal so there may be a leak.

Leaning the mixture with the EHA off improves the mpg slightly but results in rough idle (like car wants to die).

So it looks like a mechanical problem.

Ignition stuff have been renewed (plugs, cables, filters, etc) and lube job recently done with fully synthetic oil (every 3 months regardless of mileage).

I have done several preliminary checks/tests on the car.

Coolant temp sensor - measures 277 ohms at 83 deg C (within spec).Car is not running cool and cooling system is working satisfactorily.

Pulled cold start valve with engine running and not leaking.Driven car with cold start valve disconnected but no difference.

I did test my EHA current with an analog ammeter.

Key-on = 10mA
Engine on = 0.25mA
Acceleration = Current goes to -0.25mA
Deceleration = From -0.25mA, blips to 50mA and goes back to 0.25mA

Resistance across EHA is 21 ohms at 83 deg C (within spec).
Voltage across EHA connector key-on (disconnected from EHA) = 3.96V

I also took off the connector at the air-flow potentiometer and checked the resistance at the terminals = 1k ohm with the airflow plate at rest.

At pin X11/3 :

Key-on = 30%
Engine on cold/or at 83 deg C = fixed 49.7% duty cycle

The fixed 50% duty cycle reading when warm seems to indicate an O2 sensor problem.

But the problem exists whether the EHA is on or off, so I may have to resolve the open loop mixture before I can connect the EHA and try to get the car into closed loop.

I have some thoughts on the problem :

Does the zero/basic position on the AFM plate affect the adjustment of the mixture - ie, if the zero/basic position is off, would it result in a car running rich even though the mixture has been leaned?

Also, would a faulty fuel pressure regulator result in running rich and can I test it?For instance, I have heard that pulling off the vacuum hose and finding fuel in it would constitute a bad regulator.

The vacuum hose from the regulator is connected to a breather hose T.One end goes to the intake (i think) and the other goes to the valve cover and air filter housing.I am trying to take off the breather hose at the valve cover with difficulty.

What connects the breather hose to the valve cover?Looks like a kind of a check valve of some sort.What is it's function?

I hope that you experts out there (like Steve Brotherton, M.B. DOC and others) can help me out with this issue.:)

I have been to 2 indie MB shops.

One told me that my fuel distributor "is not so good" without even doing any checking - probably wants to take me for a good, long ride.The other (left the car with the guy to check) told me that my car is running perfectly, good idle, etc.All he did was richen the mixture (i had leaned it) with the EHA on and told me that he had another similar complaint from a customer and it was "normal".

I don't believe it's "normal" coz the difference in fuel mileage is outrageous!The car used to get very good mpg!

I am very interested in checking/testing further but I need help from you guys out there.:)

Sorry for the long post and thanks in advance to everyone.

You may want to check this thread out ..there is a pressure base line setting before eha hook-up...

http://www.peachparts.com/shopforum/tech-help/71584-setting-up-eha.html

I think this is unrelated but a couple of days prior to the first reduced tank of gas I got, I cleaned the air temp sensor (connected to the air filter housing) with WD40 and also sprayed a little WD40 on the throttle microswitch.

However, the air temp sensor was checked by testing resistance while blowing at the sensor.It varies and the values are within spec compared to a new one.

The microswitch also has resistance values when closed/open depending on which terminals you get the readings from, so I guess it is working.

Hope you guys can help me here.

Thanks for the link Arthur...
 

but I had read that post earlier and am looking for more info on adjustment of the mixture with the EHA off.

Any idea how the fuel pressure regulator works?

As I mentioned in my earlier post, I read that if you pull off the vacuum hose and find fuel in it, the regulator is history...is this a fact?

Earlier this afternoon, I pulled off the vacuum hose from the regulator.By accident, the edge of the hose broke off from the regulator.

However, pinching the hose and releasing it did nothing at all to the engine's idle!

Also, closing the hole for the vacuum hose with my finger at the regulator and exposing it did nothing (duh!).

I am thinking maybe the vacuum hose is clogged up.

If there is no vacuum to the fuel regulator (like my current setup coz the hose broke off), will the engine get a default enrichment?

Check out the photo I took of the regulator with the vacuum hose (in red) disconnected.Engine idles the same with or without the hose connected and car is still smoking.

Wonder if this is the root to my problem?

Any help appreciated.

<<If there is no vacuum to the fuel regulator (like my current setup coz the hose broke off), will the engine get a default enrichment?
>>

Yes . the vac to the regulator is what sets the pressure according to engine vac spec.. so, if the hose has no vac., you will get High fuel pressure [ rich] .
The pressure will actualy go as high as the pump will put out.
Try to grab some engine vac somewhere and get it to the reg
with a hose to see if the reg will lower the fuel pressure...
I don't have much info on that model, so I don't know pressure specs......

This is not the way it works on our 190E. The hose goes to the breather side of the pcv orifice, so it would be unlikely to detect much vacuum there unless there is a problem with the engine. The hose simply provides a pathway for fuel if the regulator diaphram ruptures - hopefully back to the air cleaner.

Steve

Ok.. scratch mine..
Thanks, Steve...

Thanks for your input guys.

I saw an earlier post/solution in Vadrill's post and this has confused me a little.

http://www.peachparts.com/shopforum/tech-help/19164-hesitation-accelerating-stop.html

I have the same split on the breather hose to my valve cover and I also have the same hesitation on acceleration from stop.It so happens that the "vacuum" hose for the fuel pressure regulator also connects to this breather hose at a T.

Steve - damn, I was just about to "pop" the champagne...you burst my "bubble":D!

Nevertheless, I will change out the vac hose to the fuel reg as well as the breather hose it is connected to - valve cover/intake/air filter housing.

Where do I go from here?

With the EHA off, I am still running rich and leaning the mixture till the car barely idles only results in very rough idle but still smoking.

Any ideas?:confused:

The plastic 'T' is actually the pcv device. The plumbing to the firewall side of it is at manifold vacuum, and all hoses need to be in good shape. Still, a vacuum leak would lean out the mixture, so I doubt if that is your problem. Running rich - at a guess - sounds like a sticking control plunger in the fuel distributor - not returning all the way to idle rest. Since I have never worked on one of these, hopefully you can get some more experienced advice.

Steve

Steve

sounds like a sticking control plunger in the fuel distributor - not returning all the way to idle rest

I have yet to check my Air Flow Meter plate.But if that were true, then a zero-position of the plate on the venturi that is too low will cause fuel to leak.

Anyone can confirm if this is correct?

If so, then the zero (and basic) position of the AFM plate is crucial in getting the right mixture.

UKEvo had advised me to do this earlier but I thought it only had bearing on the idle.Never looked at it from the plunger point of view.

But I hope someone can help me confirm this.

Also, if the plate is set too high/low, what is a good way for correction?

I may be wrong but I read somewhere that if it's too high, you tap it down (somewhere) and if it's too low, you can pull lightly on the bolt at the top of the plate.

Anyone?:confused:

I wouldn't guarantee the airflow meter plate will track the plunger, if the latter is sticking. However, I suppose the plate rest could be gummed up and preventing a full return, or a problem with the linkage, and all cause the same symptom.

If it needs adjustment - which seems unlikely given the way the problem developed - I would take the airflow meter out for examination, leaving the distributor attached.

Steve

Is it OK to push the plate down and spray a good dose of carb cleaner in there?

Fuel pressure regulator
 

With the vacuum hose pulled off, I can see fuel pooling in the regulator, and some of it has seeped out.

I have read from other posts that if fuel leaks out from this end of the regulator, it is shot!

If this is true, then my regulator is shot.

Normally, how does a regulator go bad?And if it does, what effect does it have on the car?

Really in need of information and at the same time, really keen to learn how the car works!:D

Hope you guys can help me out here.

Thanks, y'all.:)

"Is it OK to push the plate down and spray a good dose of carb cleaner in there?"

Probably, but the bottom of the plenum is rubber - make sure the cleaner will not harm that. I used rubbing alcohol on shop paper towels, pushing down the vane and thoroughly cleaning the inside of the venturi and the contacting edges of the vane. Do this with the engine off - it will immediately stall if you try it with the engine on, and you don't want to be there if an intake backfire should occur, anyway.

Removing the distributor/airflow meter unit isn't too difficult or messy, and the rubber plenum can then be removed for complete inspection of the mechanism. If your idle circuit hoses are old, why don't you replace them and the rubber plenum at the same time as the regulator, and it will make this operation just an extension of that repair. Order the saddle that holds the rotary idle air valve too, as it gets hard and brittle and difficult to remove non-destructively. Aftermarket, none of these parts are very expensive.

Steve

Steve

I replaced the idle circuit hoses and have an appt to get the fuel pressure tested wiht a techie.

On my own, I tried to get the fuel distributor off to see if it is leaking fuel.

Thought of getting just the cold start feed off to get at the 3rd torx bolt that holds the distributor down...but NO GO!

Despite using 2 open end spanners for the operation (duh!), it would not come off!The cold start fuel line would twist together with the nut attached to it.If I had turned further, I'm sure the line would break!But I did get to the point where fuel was driping out from the crack but no further.

I will have to get the same techie to help me with this, but it will be next week coz it a National Day weekend!

By the way, I've seen In my Haynes that the fuel distributor has an O-ring but I need the part number!Parts guy says he has never sold one!Mine, although is a 1.8 it is an 8 valve 102, so it should be the same part as the 8 valve 2.3s in the US.

Thanks again, Steve.

Fuel pressure regulator
 

Changed out the breather hoses from the air filter housing/valve cover/rotary idle actuator including new plastic T and joint.

Also swapped out the Fuel Pressure Regulator coz the old one had a little fuel leaking out the vac hose.

Readjusted fuel mixture with EHA on.

Drove car hard - 15 minutes of sheer pleasure, car drove like new.No hesitation from stop with A/C on.

After 15 minutes of pleasure, going up a slight slope at 80km/h, car started feeling like it was bogging down.

Felt like I was loosing power (or flooding).

When I cleared the slope, coming down the slope I could feel the familiar surging of the engine; and noticed that car started to smoke (running rich).

At a stop light, when accelerating, car hesitated severely, and surged while accelerating, still smoking.

What gives?

I stop the car, pull off the EHA and leaned my mixture till I got driveability back with the A/C on.

So now I'm back to square one.

I noticed however, that this problem of running rich seems to happen when the car is warm (with the EHA off - to exclude the electronics from the equation; pure mechanical injection).

Normally, the car is very driveable when first started; albeit hardstart (coz EHA is off).

Could any of the sensors affect the mechanical injection with the EHA off?Don't think so but I'm not sure.

Any ideas?

HELP!!!:(

Oh yeah, forgot to mention that fuel smell in the oil (checked at dipstick) was the other factor that prompted me to change the Fuel Pressure Regulator.

In any case...HELP!!!:confused:

Does the engine achieve closed loop control? A common easy view I take on these systems is to watch the activity of control at various different constant engine speeds, preferably under load. My break out leads are about ten feet long and I monitor while controlled driving.

The degree of control shouldn't be different by more than ten percent at any constant load. If the system can not maintain control the EHA current will peg plus or minus 12ma. The characteristic of control is what is required to evaluate. What happens to closed loop? Does it peg lean or rich?

Before doing any of that be sure that the airflow meter moves freely and there is proper 2-4mm free movement before the piston is lifted; and that the point of engagement is right at the base of the flat vertcle cylinder at the center of the cone..

Beyond this, one will need to evaluate system and differential pressure and the relationship to electronic control or you need to flow test. Included is a picture of a flow test on an electronic injected v8 BMW. The same equipment (differential flow meter) was originally designed for K-jet.

Thanks for your reply, Steve.

In fact I have been working on this problem for the past 2 weeks or so and I have been going thru' each and every sensor in the system and testing it to specs obtained from the forum/web/Haynes manual and where all else fails, I compare the readings to the parts in my kid brother's 190e 1.8 (same year/model).

Just to name some of the items - air flow potentiometer, EHA, engine temp sensor, air flow sensor, cold start valve, fuel pressure regulator, etc.

I had also DIYed a harness for the EHA to connect to my multimeter so that I can monitor my EHA current.

I had posted the results earlier but nobody seemed to be able to make anything of it (maybe my results were screwy) or maybe nobody took notice of my post.

In any case, here they are :

Key on : 10ma
Engine on : 0.25ma
Acceleration : -0.25ma
Decel : 5ma, -50ma then back to 0.25ma

I have also done the zero/basic position of the air flow plate.

At X11/3, I am getting 50% fixed duty cycle when warm which could mean a faulty O2 sensor or mixture being way off and system unable to correct (is this right?).

I have disconnected the EHA to eliminate the electrics from the equation.

It seems that even when the mixture is lean (to the point that the car barely idles at warm startup), it is still running a little rich - black smoke from exhaust when revved but slightly less than before.

I pulled the vent hose off my fuel pressure regulator and found fuel in it - so it was replaced.

I retuned the mixture with the EHA on and when I got the idle close to perfect (no flat spots), there was no smoke from the exhaust so the problem seemed to have been solved.I forgot to check X11/3 at this time coz I was too eager to get on with the test drive.

Car ran superbly for 20 minutes till I reached a slight incline.Then the car seemed to bog down like before and I see black smoke coming from the rear.

I go to a remote area for testing, and I find that the car is back to running rich as before.Hesitating severely on acceleration as though it was flooding.

I disconnect the EHA and leaned the mixture till I got driveability back (even with A/C on) albeit rough idling.

This was 2 days ago.

Visits to 3 different indies got me the same replies - bad fuel distributor; though I was skeptical, it seemed possible to me coz that would explain why I couldn't get the right mixture even with the EHA off.

BUt the whole process also made it seem to me as though the car was dumping more fuel than needed - as though it was receiving "false air" info.

With the high cost of the FD and unavailability of spares here (EHA and O-rings not available separately - only complete assemblies), I had to sit down and think it thru.

My options were to get a used FD or tackle the problem on my existing FD (if it were possible).

This m,orning, at a whim, I bought a can of carb cleaner.With the aid of my spare vac hose (I also replaced the split breather hoses, regulator vent hose and pcv), sprayed the underside area of the FD by pushing down the air flow plate.

Test drove the car.

Damn!

Like new!

Really!

No black smoke (not that I can see from my rearview mirror) and no hesitation from acceleration.Also no bogging down when accelerating at speed and now the car can go above 80km/h (not before) without effort.

I am now monitoring the fuel mileage to see if it is improving.

I have not richened the mixture and neither have I reconnected the EHA as I want to keep the variables maintained and see if the mileage improves.

Sorry for the long post but I just had to get this stuff off my chest.

Steve, I appreciate any thoughts you may and apologise if my sequence of testing seems irrational.

Please advise me where necessary coz I enjoy working on my 190e (and driving it) and I wanna learn as much as I can about it.

Thanks.:D

DIY EHA harness
 

By the way, I kept getting questioned by pedestrians if I was doing "race testing" on my car coz they could see my wire harnesses from the bonnet and the FLUKE digital/SANWA analog multimeters in the car!:D

Cheers.

I've got my fingers crossed and hoping the best for you. I hope I get a chance to work on mine this weekend. I sure miss driving that thing!

Unfortunately your problem does sound a lot like one way the fuel distributer fails.

As easy as all this electronic testing is, it is based on the concept that proper application of control gives the proper measure of control.

Overall, it seems to me that your electronic controls are functioning they just keep getting different results from the same control.

One way this happens is when the EHA can not control. The way the EHA controls is by its ability to function as a precisely controllable leak to fuel return from the lower chamber of the fuel distributor. The upper chamber pressure is being controlled massively at the external fuel pressure regulator. From the boundless (in theory) source of regulated pressure fuel a small oriface openning allows fuel to flow into the lower chamber. it flows in at a precise rate and if the container were totally contained in a small time the fuel woul be at the same pressure as the upper chamber. As it happens the flow rate out through the EHA when disconnected (zero ma) is slightly greater than the flow in, allowing the pressure to be reregulated lower than system pressure. The difference in these two pressure the lesser subtracted from the greater gives differential pressure.

As long as there is differential pressure fuel can flow to the injectors. The proper dif press at zero ma is .4bar. Total lean correction -12ma cuts the diff press by .1bar (approx) and decel cut-off -60ma (-50 in your case which I think is right) produces zero diff press and no fuel flow.

The fuel distributor problem I have seen involves a restriction in the supply hole to the lower chamber. This causes the EHA leak to be greater by comparison and one case had a zero ma diff pressure of 1.4bar. The other one I can remember was less but still around one bar.

When you look at the pressures used for proper control: Base - .4 bar, lambda correction ,1bar lean or .1bar rich from .4, one can see how devastating to control a diff pressure of 1.0 or 1.4 can be.

one way this can be suspected from electrical testing is to watch your lambda set point (closed loop median amprage). If at idle you have closed loop control median about zero ma then by holding the engine to 2000rpms you should still have the same median. if it goes off the scale I'd look at pressures.

Thanks for the info, Steve.

Theoretically, it does seem to me like a failing fuel distributor but I am not sure, YET.

Luckily, I still have the EHA harness connected to the EHA with the leads near the driver's console for testing.

I will hook up my ammeter again and look at the lambda set point.

At this point, even if all tests conclusively confirm the replacement of the FD, I am already very contented.

I have got more information in this thread than I could ever dream of and the real reward to me is fully understanding how my car works!

Thank you, Steve, for taking the time to convey the info that you have.

Cap'n - I have had my fingers crossed since this morning; but I seriously doubt that the problem will be solved as easily as that!:pBut who knows...

I'll let you guys know how it goes.

Cheers.:D

Before I do anything else...
 

I'm gonna take the car out for a blast down the freeway while I still have it set lean with the EHA off.

Just in case the O2 sensor is fouled up, I'm gonna run the crap out of it!:p

Cheers.:D

This sounds very similar to the problem I was having with my 2.3

What happened originally was the engine was replaced, and whoever was getting it to run, did not know that older models of a 190 have different amperage in the EHA then the newer models since 86 I believe.

So my car was set for 0mA in the EHA, which caused it to actually run really lean, and as a result the car hesitated like no tomorrow, but was driveable.

After testing and testing and learning all the thories of the engine, all it took to correct the engine was a slight turn of the air/fuel mixture on top of the Fuel distributor and the car was running like new ever since.

One thing does leave me worried however, on the beginning, azhari metnioned that he got 450km out of the car before the fuel light came on. I can only get 450km out of the car from pure highway driving, on the streets I get up to 350 and although I never let the fuel light go on, I have to pump up to 45L of gas to fill up, and according to the manaul, I only have a 40L fuel tank.

Now what I would like to find out is why my car would not start when I had the mixture set right on 8mA. I had to richen it to get it to start, with the correct mixture setting it would not start. Can anyone think of anything?

This is cold or warm starts, but mostly warm if I remember correctly.

I would really love to be able to get 450km out of my car on regular streets and not just pure highway driving.

And it also looks like I have about 11 months to do this before my final emissions test which I would like to pass without any problems :)

xp

xp

I normally fill up with about 44 litres when the fuel light comes on after doing 430 to 450km city driving (approx. 10km/litre).

My 1991 190e 1.8 Euro RHD has a 55 litre fuel tank as per my Haynes manual.

I have yet to reconnect my MM to my EHA harness and take the readings again while driving.

A recap on my car's existing setup - EHA off and fuel mixture leaned to the point that it idles a little rough.

Problem - car running too rich with EHA on/off, black smoke and severe hesitation off the line.Suspect "more than necessary" fuel being dumped while engine is running.No external fuel leaks and gas mileage horrible - 260km when fuel light goes on.

Meanwhile, my latest findings since spraying the underside of the FD (by pushing down the airflow plate) is that now when I park and leave the car idling, it doesn't leave a sooty mark on the pavement.Before, 2 minutes was all it took to get a sooty spot the size of my palm on the pavement.

Before the carb cleaner trick, even with the EHA off and mixture leaned, the car would still hesitate slightly off the line and smoke if accelerated hard.Fuel mileage closer to 300km when light goes on.

My tank was only left with 1/4 when I did the carb cleaner thing so I'll top it up today and clock the fuel mileage.

If it improves, my next step is to richen the mixture with the EHA on and try to get the car in closed loop.

By the way, I have been following your threads for a while and all I can say is GOOD JOB!

I will report my findings and further checks/tests as I go along.

Thanks guys.

Cheers.:)

Steve Brotherton,

Drove with my MM hooked up to the EHA harness.

Key on : 10ma
Warm engine idle : 0ma
Accel : -2.5ma (2000rpm)
Decel : From -2.5ma, to 5ma, -50ma, then 0ma.

Seems like I'm screwed.

By the way, having sprayed carb cleaner onto the underside of the FD on Saturday improved performance and fuel mileage slightly improved.

This evening, problem cropped up again.

Severe hesitation at accel, smoking and bogged down performance (flooding).

Pulled aside, waited a little, did the carb cleaner thingy (3 short squirts).

After 15 minutes, drove off and performance much better, but still smokes on hard acceleration.

I noticed a major difference after the cleaner trick is that the engine feels more free-revving immediately after application.When it starts bogging down, the accelerator feels heavy in that the car will not rev up easily.

Mind you, I'm driving with the EHA off and mixture leaned till idle is rough.

Correct me if I'm wrong, but isn't the FD plunger lifted proportionally to the deflection of the air flow sensor plate?

It seems like the plunger is sticking - it stays in the upper position even though the air flow sensor plate moves back to basic position upon release of the accelerator pedal.

I have read from my Bosch fuel system notes that the control pressure opposes the force that is applied to the control plunger by the air flow sensor plate pressure.

Hence, if my regulator is new, it would seem that my fuel distributor is toast!

Or is my plunger gunking up?

But if so, I think it would have been resolved by the first application of the cleaner "trick".Now, I have applied the cleaner twice since Saturday.

I wonder what the relation is between the cleaner "trick" and the fuel distributor plunger?

sbourg - about 2 weeks ago, you posted your guess that this problem "sounds like a sticking control plunger in the fuel distributor - not returning all the way to idle rest".

At this point in time, I think this is the problem.

stevebfl - if this is the case, is it the point of no return for my FD?I am on the verge of bleeding it, taking it out and soaking it.Would this do any good?

Appreciate any thoughts you guys may have.

Thank you.:(

EHA current
 

Stevebfl

Appreciate any comments you may have on my EHA current values.

Thanks.

Bummmmmmmpppppppp...

You haven't given me much with the values three posts ago.

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.

In other words I'm looking for how the electronic feedback views the different fuel flow rates. For these purposes we must leave accel enrichment out and decel cut-off is only of value to prove it happens.

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.

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.:)

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.

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.

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.

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!:D

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

I thank you for your patience.

Cheers.:)

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?:confused:

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.

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.:)

Steve

I missed this paragraph.

I guess I don't have a vac leak or my car would run lean.

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.

Or I dare you to figure this one out. Pay attention to the units of measure. Car is a 88 300SE

Or like this:

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...:(

your 190E problems
 

:confused: 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?

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

Here are some photos from other posts...
 

Top half.

Bottom half.

Diaphragm.

Taken apart.

I have not taken mine apart.

These photos were from Cap'n Carageous' and Hurshi's (I think) posts.

Meanwhile, with the EHA off, my car runs well when cold but crappy when warm - severe hesitation on acceleration, smoking badly on hard acceleration, surging idle...:(

What sort of symptoms do you see on your car which is prompting you to take the FD apart?

By the way, the tech who was supposed to fuel pressure test my car simply diagnosed a "bad FD" without even willing to diagnose further!So I haven't got any results...:(