EHA current values for European spec 190E?
 

Hello everybody!

I've got a European 190E with 2.0 litre cat M102 and automatic transmission year model 1990. I have found great information on this forum about the KE-Jetronic (CIS-E) EHA current and the way it affects the air/fuel mixture. Have you got data for the European 190E 2.0 or 2.3 model? I haven't been able to measure the EHA current yet, but my car seems to be out of breath at higher revs and the mixture could go lean. I would appreciate EHA current values for A) power on, engine off, B) idle w engine warm and especially C) full load at WOT.

Has anybody tried to modify the EHA current like the VW people do? Autotech makes a power module for the VW KE-Jet, more info at http://www.autotech.com/prod_engine_pwrmod.htm and http://www.autotech.com/instructions/i215200.pdf . Could this work with the MB KE-Jet or are the currents too high?

Thanks
tomant

Welcome,

The EHA current value with Key-On Engine-Off is 20ma.

ON a properly adjusted engine the running current value is a cycling current of positive & negative.

Thanks, 'Doc. The current cycling between positive and negative stands for closed loop and lambda correction, I believe. How about the full load enrichment at WOT, are there any typical current values for that?

tomant

Full Load
 

full load or Idle should read the same or very close to it.you will need to make a harness so you can separate the plug from the valve,one is just an extension the other rigged up so you can place your meter in series, the line closest to you is the one that needs the junction. When the car is running the voltage should read -0 to+ 0 it will bounce back and forth constantly,Each time you adjust the 2.5 m/m allen screw,you must reset the fuel mixture at the air fuel 3m/m adjustment,It will take several times to set if it is incorrect.Take your time and be sure to count your turns and the direction of turns,even write them down very important to know incase you must go back the opposite way.NOW THIS IS VERY IMPORTANT, the 2.5 m/m that is just below the brass screw,has no NO tension on it,blow the fuel out look down in to it and see its position, place your allen wrench into it and turn it 1/8th at a time, If the voltage goes up then you will need to go in the other direction. Any other help you need you can find on one of my post on this subject.GOOD LUCK JNT:book:

JNT are you talking about voltage (volts) or current (amps or rather milliamps)? MBDoc told that the current key on-motor off is typically 20 milliamps (mA). The resistance of the EHA is about 20 ohms so it gives a voltage drop over the EHA that is about 20*20/1000=0.4 V or 400 mV. The change in EHA current makes a change in the mixture strenth. On the other hand we know that the KE Jetronic full load enrichment should be about 10% over stoichiometric (AFR 14.7) in the rpm range 1500 to 3000 and 5% in the range over 4000 rpm correspondingly (Maisch). I just wondered if anybody has measured current readings (and AFR readings) at full load and WOT, because I haven't found accurate values anywhere. The only graph of the current - AFR - relationship I found on the book by Probst, but it was symbolic without exact values..

References:SAE paper "KE-Jetronic - A new Continuously Injecting Electronically Controlled Multipoint Injection System with Limp-Home Capability" by Wolfgang Maisch, "Gasoline Fuel-Injection System KE-Jetronic", Robert Bosch GmbH 2000 and "Bosch Fuel Injection & Engine Management" by C. O. Probst, Bentley Publishers

tomant

The test of EHA is done in ma. the x11 pin 3 is in volts dc about 10v.unless you have a meter that will read duty cycle.sorry I do for get myself when I begin to explain the proses,my mind tend to jump from one thing to another.Thank you for catching me. JNT

I made a harness for a digital multimeter and went for a test ride. The Key-On Engine-Off current was 20 mA and the overrun value -50 mA as expected. The current fluctuates between -4 and -5 mA at idle and shows a constant value of -10 when cruising above 50 mph (80 km/h) and also at WOT accelerating. There was no full load enrichment, the current was always -10 mA at normal driving conditions (with automatic transmission).

Questions:
A) Is the basic mixture setting too rich and is that why the EHA is always trying to lean out the mixture?
B) Is the lull load switch out of order or does the leaning effect override the full load enrichment.
C) How should I proceed?

tomant

You said euro spec. Does it have an oxygen sensor? If it does the reading yiu describe are for a car adjusted too rich. The system is correcting lean.

Yes it has an oxygen sensor, cat and adjustable ignition with EZL KAT (not R16). I'll try to get the current near 0 mA at idle by adjusting the mixture screw. Maybe that will fix the full load enrichment too.

tomant

Yes it will, do try to lean out the EHA 2.5m/m allen as it was described go slow and be patent,you will get it,remember each time you reset EHA you must reset the fuel mix. Lean the EHA, richen the mix.JNT

When I turn the idle mixture leaner about 1/4 turn the current slowly drops from about -4 mA to full rich +12.5 mA. The current at cruise speed is now about -7...-10 mA and always -10 mA at WOT. I cant keep the current around 0 mA at any speed. There is still no full load enrichment current. Could the lambda sensor or the full load sensor be inactive or faulty?

tomant

Idle?
 

when you turn the EHA and the reset the idle mix,is that what you meant?
If you turn the EHA setting clock wise 1/8th then reset the mix just some richer to smooth out idle, you don't do the mix to get your m/a change at EHA! JNT:book:

I am only trying to find what is wrong with the mixtures by reading the EHA current. I have only adjusted the idle mixture (CO adjustment screw).

tomant

adjust to change
 

If you readings are so far off you will have to open the EHA and make the adjustment.you cant get there from the direction your trying.JNT:singer:

I adjusted the screw inside the EHA 1/2 turns CCW and the CO screw a little to compensate. Now the EHA current is around +-0 mA at idle and between 0 and -2 mA at 50 mph (80 km/h) cruise so it seems to be about right. When I accelerate lightly (not WOT) the current is about -4 to -7 mA and acceleration at WOT brings the current to -10 mA. The throttle valve switch works OK in closed and WOT position. I still can't get the EHA current to positive values at full load. The car is working fine so should I just leave it as it is or is there anything wrong as there is no positive full load enrichment?

tomant