Adjusting Fuel Mixture (Problem with checking idle duty cycle) - PeachParts Mercedes-Benz Forum

JamesDean · #1 03-18-2009, 04:08 PM

If i have to put it in diagnostic mode to read duty cycle..what is it outputting to my scope throu x11/2 x11/3 ?

taken before any adjustment were done. all i did was connect up to x11
http://i98.photobucket.com/albums/l250/MafiaNicky/idleafterafewminutes.jpg

If it is in normal mode..why would it output anything at all?

professor · #2 03-18-2009, 05:30 PM

Was that at idle?
From the looks on that waveform, it looks like a lean mixture. My 2 cents!

JamesDean · #3 03-18-2009, 06:15 PM

Quote:

Originally Posted by professor

Was that at idle?
From the looks on that waveform, it looks like a lean mixture. My 2 cents!

Yes, that was @ idle. That reading was done just before I started adjusting things. I did teh EHA first and got it to ~45-55%.

I adjusted the Lambda tower once or twice, then lost signal.

Now when I check duty cycle, it fades out as in this video:

http://s98.photobucket.com/albums/l250/MafiaNicky/?action=view&current=DutyCycleScope.flv

professor · #4 03-19-2009, 09:55 AM

Put an Ammeter at the EHA (in series) and measure the current. You should oscillate around 0 Amps -1mA to +2mA. That should tell you that the EHA is working at regulating the pressure differential inside the fuel distributor based on the feedback.
Check your fuel pressure readings:
Main pressure, that is before the distributor (the cold start outlet is a good place).
Lower pressure, that can be done via the test outlet on the distributor.
You should get a specific difference between the two, check your manual for the value.
If that is off and you tried the EHA to get it then you have a problem with a CIS component. You will have to trace that throughout the fuel lines.
In your case, it's possible that the computer can't keep up and from the looks on that signal you may have set it where it went rich. You could see it drift then it's like the computer decided not to play no more

Please note that EHA and Lambda adjustments must be done a hair at a time. NEVER full turn!

JamesDean · #5 03-19-2009, 03:04 PM

Quote:

Originally Posted by professor

Put an Ammeter at the EHA (in series) and measure the current. You should oscillate around 0 Amps -1mA to +2mA. That should tell you that the EHA is working at regulating the pressure differential inside the fuel distributor based on the feedback.
Check your fuel pressure readings:
Main pressure, that is before the distributor (the cold start outlet is a good place).
Lower pressure, that can be done via the test outlet on the distributor.
You should get a specific difference between the two, check your manual for the value.
If that is off and you tried the EHA to get it then you have a problem with a CIS component. You will have to trace that throughout the fuel lines.
In your case, it's possible that the computer can't keep up and from the looks on that signal you may have set it where it went rich. You could see it drift then it's like the computer decided not to play no more

Please note that EHA and Lambda adjustments must be done a hair at a time. NEVER full turn!

I will check the current in the EHA when I get home tonight.

I don't have any tools to check the pressure however...
Any recommendation on a cheap set of gauges?

professor · #6 03-19-2009, 04:33 PM

Yes, Harbor Freight has a nice CIS set. That's the one I use which is meant for occasional use (not a pro that takes a daily beating).
I used it on the Benzes and on a Ferrari it works just fine.

JamesDean · #7 03-19-2009, 07:03 PM

could you point it out to me ?

http://www.harborfreight.com/cpi/ctaf/Category.taf?CategoryID=455

I did find one that like $12 but it says "except Bosch, CIS"
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=92699

Is it this:
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=93547

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