Duty Cycle reading and questions......
 

Am I doing this right?
Testing and setting the Duty Cycle on a California spec 1988 300TE with Craftsman meter set to %.
Setup...
Key in, Ignition on, diagnostic set to solid LED by holding for 2 seconds and then again.....

Red into red on the meter and black into black or sensor plug on the meter...
Ok, on the car, first I plug the Red lead into socket pin 3 and the black into 2...

http://img.photobucket.com/albums/v2...yreading3e.jpg
Reads 14.8%....????


Reverse the wires... black to 3 and red to 2... reads 85.1% as it should for Cal spec car.

http://img.photobucket.com/albums/v2...yreading2e.jpg


Retest with red removed from 2....... no change?????

http://img.photobucket.com/albums/v2...yreading4e.jpg


Here is the reading using Black to 3 and red to 2... engine warmed up and running nice..... fluctuates about 50% +- 5ish.

http://img.photobucket.com/albums/v2...tyRunningE.jpg

Now, is this the right way to do it?
Is that reading about right?

I have not closed the charcoal canister connection because I dont know which one it is!

That is correct assuming the engine is not fully warmed up on the first pics. See the engine needs to be at 80C for proper setting and checking. Anything before that will be rich due to warmup phase. Also at first before the cat is warmed up to operating temp and the O2 is at operating temp the reading will be wrong. The O2 is ignored at first until it is warm and you will get no fluctuation and a static reading.

First photos were with engine off and cold.

Last one is with engine running and 80deg plus showing.

Correct with engine at operating temp.
But you want the red in pin 3 and the black in 2 or the black connected to a ground source like a shock tower bolt. You'll probably get around the same reading becuase your car is fluctuating around 50% anyway.

I don't think that is correct Yal... since he is getting the correct KOEO reading (85%) with that test configuration... that would be the way to run the test.

Oh ok. Ignore me :)
But isn't that weird. I though pin 3 was the pin to read?

Merkey,

At least you're somehow getting an 85% reading for your CA car!
I still can't get my LED to stay in continuous on mode.

In your picture #3, when you "Retest with red removed from 2.....no change???, is the red lead really not connected to anything?

In your picture #4, is the 46.6% at engine idle? What is this reading at idle and at 2,500 rpm? (should not differ by more than 10%)

Can you give me the MB and Bosch part # from off your ECU? (my CA '90 300te should have the same).

Next week, I will be taking mine to a local indi. He is going to allow me switch out my ECU with his wife's car. Should be interesting.

Mark

Agreed.
I haven't found a satisfactory answer as to why but I have the same circumstances when I read the 86'. It confused me quite a lot when I first started trying to diagnose an emmissions problem. Finally I reversed the pins and got 70% KOEO as a baseline. I have heard refrences to mercedes doing it backwards (maybe %-off instead of %-on) but I'm not sure to which years this applies.

:confused:

Might be interesting to try what's mentioned below in the "update" section of the post.

http://www.peachparts.com/shopforum/tech-help/56144-86-190e-2-3-no-signal-pin-3-diagnostic-port.html?highlight=pin

Interesting math is the following thread as well:

http://www.peachparts.com/shopforum/tech-help/71854-how-do-i-use-my-fluke-read-duty-cycle-2.html?highlight=pin+red+duty+cycle

I've been scratchin' my head all day on this one? Everything you read here indicates pin 3 is the port to put Mr. Red on. Apparently not.

Ok... here is some info..
The Black Meter cable plugs into a port labeled "COM".
I assume that is why I get the correct 85% reading in KOEO.
I figured that if the 85% was showing, I was doing it right!

Mark: It was our other post that prompted me to post this... I was unsure if what I did and posted was correct... sorry it did not help you.
The red lead was not connected or grounded to anything... but if it is it still reads 85%.
Yes, the 46% reading was photographed at 85 deg running at idle...rolling around 45 to 55.... the 2500rpm was a little higher, but about 50ish.

Anyone have any thoughts on the Charcoal can purge line?
Would it effect the duty if I did not disconnect it?

Yes over 60 degrees there is a vacuum valve that opens thus opening the check valve to the purge canister. Thus making it able to suck air in once the throttle is opened. What is the problem with the purge canister.

Mct... the problem is that I dont know which vac line it is to plug it and get a correct reading!
Any ideas?

Merkey,
What source instructs you to disconnect the purge line to get an accurate duty cycle?

Any chance that I can get those part #'s off of your ECU?

Mark: From the Landis web page... Item 3.

My son is out driving around this evening... where is the SN on the ECU?