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  #1  
Old 07-31-2008, 09:27 PM
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Location: Sealy, Texas
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Cis-e ecu

!987 260E
The car will not run with EHA plugged in. If I unplug the eha and tune the vehicle for best idle I can run it all day, as soon as I plug the eha back in the car stalls. If I tune it with the eha it idles fine but fouls out the plugs in less than 4 miles.
I've changed the FDU, eha, temp sender, idle motor,cap, rotor, wires, EZ unit and ovp. When I try to read the mil amps on the eha I get a constant .059 readout. Also I don't seem to get 10volts at the cold start injector. This is why I am now wondering if the cis-e ecu has gone bad, even though I get different results when I either plug the eha it in or unplug it.

Michael

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  #2  
Old 07-31-2008, 09:33 PM
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I also purchased a fuel pressure tester for CIS and the pressures are correct as per the manual
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  #3  
Old 08-01-2008, 08:43 PM
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bump
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  #4  
Old 08-02-2008, 01:54 PM
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Did you ever try changing the O2? Perhaps just try unplugging the O2, see if that changes anything.

Jonathan
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  #5  
Old 08-02-2008, 03:39 PM
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I assume your reading is really .059 amps, which actually means 59 mA. So for some reason the brain thinks you really need enrichment. Could be the oxygen sensor or the coolant temp sensor. Does this engine have an airflow sensor?
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'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #6  
Old 08-02-2008, 05:20 PM
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Thanks for the input,
The 02 sensor is new. I have changed everthing except the ecu and I have the same problem of running rich. as I had with all of the original equipment. Nothing I have done so far has had any effect on the problem.
I could probably return all the original parts and still have an engine that will not run with the eha plugged in.
Here's what I don't understand, if the engine is tuned without the eha plugged in, why, when the eha is plugged back in does the system not just fine tune the motor, instead of stalling it?
Is the ecu on this vehicle a unit with a history of design problems or has it been fairly reliable?
I am not aware of a airflow sensor on this vehicle. The availability of shop manuals etc for this car seem hard to get. I subscribe to Mitchel on Line for this car, and even they don't have a vacuum diagram for the 260E.

Once again thanks for your input
Michael
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  #7  
Old 08-03-2008, 07:44 AM
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With KE-Jet, the electronic-hydraulic actuator (EHA) on the FD doesn't just give the mixture a little bit of trim, like K-Jet with lambda. It provides the enrichment for warm up and acceleration as well. I think 59mA is nearly the max for enrichment. So when you plug it in, it's reducing the control pressure and drivng the mixture to extreme rich.

In the messing around I've done with both flavors of K-Jet since 1999, and reading stuff on web sites, I can't recall a confirmed case of a brain going bad.

One last thing to check. The throttle switch. Make sure it is not plugged in backwards or damage and sending a wide-open signal to the brain.

What mA reading do you get with key on? I believe you should see 25mA. This would be an indicator that the brain is still alive.
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'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #8  
Old 08-03-2008, 10:26 PM
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Thanks Chuck,
2 new things to try. Throttle switch and 25mA at eha with key on. I'll check both of those tomorrow.
I'm excited two new things to try.
Michael
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  #9  
Old 08-04-2008, 07:52 AM
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Something else

Some of this is coming back to me from my 300E. I believe that in addition to the throttle position switch, your car also has a potentiometer that provides the brain with information about the depression of the sensor plate. If this is screwed up and sending a bogus signal to the brain, it could cause the troubles you describe.

There should be a test for this in your Mitchel documentation.

You used to be able to buy the pot from Bosch, but now I believe that you have to buy the entire mixture control unit.
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #10  
Old 08-04-2008, 06:18 PM
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Well Chuck my euphoria was short lived.
KOEO eha reads 059.9. Depending on which way the leads are plugged, in it reads either pos. or neg. but still 059.9. (what is the correct connection, ecu to meter pos. meter neg to eha or the other way round, nobody seems to know)
I can unplug anything, C02, temp sender etc. nothing budges it off of 059.9.

The airflow sensor (the no longer available part) I could only find the measurements for adjusting it. 0/70 volts DC +/- .10 volts. mine read .76V. when I unplugged the airflow sensor the engine revved up a little and then when I plugged it back in the throttle sensor plate got sucked down a little and the engine returned to normal idle, so it appears to have an effect on the engine.

I'm out of ideas

Michael
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  #11  
Old 08-04-2008, 10:42 PM
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I looked up the numbers on my 107 CD for the 560SL and KOEO is supposed to be 75mA. Not sure what the 260 is.

The CD says that the EHA or its wiring, the ECU, or the "reference resistor" could cause the number to be off.

The test for the EHA is, with key off and EHA disconnected, 19.5 ohms resistance between Pins 1 and 2 on the EHA connector. As a last gasp, you can plug the EHA back in and test for the same resistance at Pins 10 and 12 at the ECU harness.

If that checks out. I would start looking for a brain. A good place is car-part.com. I found one for my 380 at Strandbergs in Wisconsin.
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'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #12  
Old 08-06-2008, 01:35 PM
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Chuck,
I'm trying to check everything in oder as listed in my Mitchell manual, so there is continuity in my results. I'll post any abnormalities. Thanks for your help so far. I hope you'll be there when the results come in.
Michael
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  #13  
Old 08-07-2008, 03:12 AM
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You need to check the duty cycle:

http://www.landiss.com/mixture.htm

You will need a DVM that reads duty cycle and they are available at SEARS, for instance. Look for one that reads both Frequency and duty cycle.
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  #14  
Old 08-08-2008, 09:43 AM
david s poole
 
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did you buy a new bosch 02 sensor or one that you have to cut and solder the wires? because it sounds like the 02 is grounded showing the ecu a 0volt signal and driving the eha full rich.
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  #15  
Old 08-08-2008, 01:33 PM
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Thanks for jumping on board David.
I bought a Bosch unit not the universal. I have even swapped it out withe old one with the same results.
I am in the process of re checking the airflow sensor pot. Is there a set of numbers (ohms) that I should be able to read with the unit out of the airflow meter or must it be installed in the housing.
I have only 2 things left to change ecu or airflow sensor pot. (no longer available I'm told)

Michael

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