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1992 W124 260E
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Discussion Starter #21
Installed a new O2 sensor and the alternator brush. The carbon brushes were more than half gone.

I've 2 multimeters. The meter on the right (New) has duty cycle. Pic attached.
So my readings based on these 2 meters are:

Ports 2, 6:
Off : 12.8V
Engine running : 14.28 ~ 14.39

Ports 2, 3
New meter:
ON 3.819 V
RUNNING 11.43 ~ 11.48V

Old meter:
ON 3.76 ~ 3.78V
RUNNING 11.36 ~ 11.38V

I tried with the dial at duty cycle and this was what I got:

ON 99.8%
RUNNING 3.764%

What does all these say? Do I need to warm the car up before I carry out the procedure?

Thanks in advance...
 

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1992 W124 260E
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Discussion Starter #23
The forum used to tell us where members were by displaying the info with their avatar. Unfortunately progress has marched backward and we don't know that information without each member providing it. Silly. Anyway, yes, I understand that in KL you have challenges getting parts at a reasonable price.

As far as testing the injector seals, there are a couple of ways to do this. One is to use a smoke producing device to inject smoke into the intake system while the engine is off. The main objective is to flood the system with smoke and wherever smoke leaks out into the atmosphere, the location of the smoke is a potential vacuum leak. Another method is to use a propane torch (without the flame - just shooting propane out of the the torch head). SInce propane will have the tendency to increase the idle when it is introduced into the air fuel mixture, you can point the torch at suspected leak points while the engine is running and make note of which locations cause the idle to rise when you introduce the gas. For example, if you are pointing the nozzle directly at an injector seal (an inch away), and the idle increases only to decrease when you remove the nozzle/gas, then you have a good reason to change the injector seals.

Having said all this, your problem (stalling when you switch on the A/C) is an issue that injector seals alone will not cure. Does the A/C work when it is switched on and the engine is running?
tuttebenne, sounds like you have been to this part of the world before.

I've seen a few videos about smoke box on YouTube. And some DIYs. I think I can make one of those later to check my vacuum lines.
Are the engine vacuum lines and other vacuum lines inter connected, i.e, if I were to smoke the engine vacuum lines, will the smoke also id leaks in other parts of the car? If that makes sense..
 

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1992 W124 260E
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Discussion Starter #24
I wasn't satisfied with the duty cycle reading so tonight I tested again and the reading were ON 99.8% and ENGINE RUNNING 99.8%, too. Hmmm
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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2,299 Posts
You most likely forgot to push the yellow button on your meter while taking duty cycle measurements. So it was just telling you the frequency is 99.8 Hz. The signal is actually 100Hz.

Your duty cycle is slightly off, but that is certainly not your problem. So do not adjust it, ...... please.
It set so that the engine has more room to adjust the mixture "richer" when it needs to. That's ok, I have run my car like that for 2-3 years, have not seen any ill effect of it.

What I'm more concerned with is the fact that it does not vary too much. With a working system (O2 sensor) it should vary more.

Please report that variation when the car is fully warmed up. Normally that varies by almost 5% as the closed loop is trying to adjust the mixture constantly.

Also report the readings with warm engine both AC on and Off. Also report the readings both at idle and at 2500 rpm.

So a few more measurements to take, I'm afraid.....
 

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1992 W124 260E
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Discussion Starter #27
You most likely forgot to push the yellow button on your meter while taking duty cycle measurements. So it was just telling you the frequency is 99.8 Hz. The signal is actually 100Hz.

Your duty cycle is slightly off, but that is certainly not your problem. So do not adjust it, ...... please.
It set so that the engine has more room to adjust the mixture "richer" when it needs to. That's ok, I have run my car like that for 2-3 years, have not seen any ill effect of it.

What I'm more concerned with is the fact that it does not vary too much. With a working system (O2 sensor) it should vary more.

Please report that variation when the car is fully warmed up. Normally that varies by almost 5% as the closed loop is trying to adjust the mixture constantly.

Also report the readings with warm engine both AC on and Off. Also report the readings both at idle and at 2500 rpm.

So a few more measurements to take, I'm afraid.....
I remember clearly pushing the button to set it to %. I'll use V readings rather than %. And I'm not going to meddle with the lambda adjustment until you say so. I am quite afraid that I'll make it worse since I am not sure what's really going on right now. Lol.
 

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1992 W124 260E
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Discussion Starter #28
Next measurements: V

Warm engine AC ON and OFF
Idle and 2500 rpm

Until then... Tq dolucasi
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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2,299 Posts
It could be your meter then. What values do you get switching from Hz to duty cycle? Anything change?
Unfortunate Mercedes chose 100 Hz for the signal. Causes confusion sometimes.

Just stick to the average voltages for now and you'll be fine.

Cheers!
 

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1992 W124 260E
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Discussion Starter #30
02-Nov-19

Ports 2, 6
OFF 12.8
RUN 14.28 ~ 14.39

PORTS 2, 3
OFF 3.76 ~ 3.78
RUN 11.36 ~ 11.38

03-Nov-19

PORTS 2, 6
OFF 12.52
RUN 14.24 ~ 14.35

PORTS 2, 3
ON 3.71 ~ 3.73 RPM 750
RUN 7.03 ~ 7.04 OIL PR 2 1/3
2" 11.37 ~ 11.41
5" 11.35 ~ 11.38
7" 11.32 ~ 11.34
10" 11.25 ~ 11.27
15" 11.19 ~ 11.21 RPM 750
20" 11.17 ~ 11.2 OIL 1 1/2

AT 20" AC ON (IDLE)
CLUTCH OFF CLUTCH ON
20" 11.08 ~ 11.1 10.95 ~ 10.98 RPM 7000 OIL 1 1/2
25" 11.05 ~ 11.07 10.93 ~ 10.95 RPM 7000 OIL 1 1/4 ~ 1 1/2
30" 11.05 ~ 11.06 10.92 ~ 10.94 RPM 7000 OIL 1 1/4 ~ 1 1/2


AT 30" AC ON (2500 RPM)
CLUTCH OFF CLUTCH ON
30" 8.6 ~ 9.19 8.79 ~ 9.06 RPM 2500 AC OFF
35" 11.1 ~ 11.11 10.47 ~ 10.98 RPM 2250 AC ON
40" 11.0 ~ 11.05 10.9 ~ 10.93 OIL 3

AC OFF IDLE
40" 11.09 ~ 11.12 RPM 750 OIL 1 1/3

RESTART AFTER 5 MINUTES SWITCHED OFF
11.08 ~ 11.11 RPM 750 OIL 1 ~ 1 1/3

* NO SHAKES OR STALLING THROUGHOUT THE WHOLE PROCEDURE



TEST NEW METER HZ AND % SETTING
ON RUN
Hz 97.63 97.62 ~ 121
% 99.9 99.8 ~ 99.9

 

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1992 W124 260E
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Discussion Starter #31
Sorry for the uneven format / layout. I did this in spreadsheet, copy and paste. The actual spreadsheet

02-Nov-19​
Ports 2, 6
OFF
12.8​
RUN
14.28​
14.39​
PORTS 2, 3
OFF
3.76​
3.78​
RUN
11.36​
11.38​
03-Nov-19​
PORTS 2, 6
OFF
12.52​
RUN
14.24​
14.35​
PORTS 2, 3
ON
3.71​
3.73​
RUN
7.03​
7.04​
RPM
750​
2"
11.37​
11.41​
OIL
2 1/3​
5"
11.35​
11.38​
7"
11.32​
11.34​
10"
11.25​
11.27​
15"
11.19​
11.21​
RPM
750​
20"
11.17​
11.2​
OIL
1 1/2​
AT 20" AC ON (IDLE)
CLUTCH OFFCLUTCH ON
20"
11.08​
11.1​
10.95​
10.98​
RPM 7000 OIL 1 1/2
25"
11.05​
11.07​
10.93​
10.95​
RPM 7000 OIL 1 1/4 ~ 1 1/2
30"
11.05​
11.06​
10.92​
10.94​
RPM 7000 OIL 1 1/4 ~ 1 1/2
AT 30" AC ON (2500 RPM)
CLUTCH OFFCLUTCH ON
30"
8.6​
9.19​
8.79​
9.06​
RPM 2500 AC OFF
35"
11.1​
11.11​
10.47​
10.98​
RPM 2250 AC ON
40"
11​
11.05​
10.9​
10.93​
OIL 3
AC OFF IDLE
40"
11.09​
11.12​
RPM 750 OIL 1 1/3
RESTART AFTER 5 MINUTES SWITCHED OFF
11.08​
11.11​
RPM 750 OIL 1 ~ 1 1/3
* NO SHAKES OR STALLING THROUGHOUT THE WHOLE PROCEDURE
TEST NEW METER
ONRUN
Hz
97.63​
97.62​
121​
%
99.9​
99.8​
99.9​
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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I do not see much that is wrong with those measurements. Except the fact that the voltage should be varying a lot more than 30-40mV in any of the tests for idle. It should be more like 0.4V or 0.5V or maybe even higher.

That is only a variation of less than 1% of the full range. So my suspicion is that your lambda control is not doing much at all.

This maybe the time to pull the carpet off the passenger side floorboard and gain access to the oxygen sensor connector.
Then you wedge a skinny wire in the connector by first disconnecting, then placing the wire in and re-connecting. That is your hot. The ground is any chassis ground locally. I generally use the door strike plate.

With the engine warmed up you should see the voltage swinging from 0.15V to 0.9V or so every 2 seconds. If it is not doing that, then there is something wrong with the O2 sensor or the controller on the other end.
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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2,299 Posts
Also, you are no longer reporting shaking or stalling? So what happened to that? Is that gone for now?
 

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1992 W124 260E
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Discussion Starter #35
I do not see much that is wrong with those measurements. Except the fact that the voltage should be varying a lot more than 30-40mV in any of the tests for idle. It should be more like 0.4V or 0.5V or maybe even higher.

That is only a variation of less than 1% of the full range. So my suspicion is that your lambda control is not doing much at all.

This maybe the time to pull the carpet off the passenger side floorboard and gain access to the oxygen sensor connector.
Then you wedge a skinny wire in the connector by first disconnecting, then placing the wire in and re-connecting. That is your hot. The ground is any chassis ground locally. I generally use the door strike plate.

With the engine warmed up you should see the voltage swinging from 0.15V to 0.9V or so every 2 seconds. If it is not doing that, then there is something wrong with the O2 sensor or the controller on the other end.

The positive pole of the mmeter is connected to which colour wire, black or any one of the 2 white wires? And the negative pole of the mmeter goes to any chassis ground?
Sorry, I have difficulty most times with electrical connection.. Lol

I'll do this this afternoon.

BTW, the wires are located under the carpet on the driver's side... This is a right hand drive country..
 

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1992 W124 260E
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Discussion Starter #36
I tested power from battery to connectors first. Connect black pole of mmeter to battery and red pole to wires of connectors on the engine side and got these numbers :

At battery: 12.52V
ON key:
Brown wire (1) - 0V
Black/Red/White (2) - 0V
Green - 0.44V

My conclusion is, there is no power going to the O2 sensor.

I also found in one Mercedes book that the
  • Brown (1) wire is Ground,
  • Blk/Red/Wht (2) - goes to pin 87 of Fuel Pump Relay
  • Green - goes to pin 8 of KE control unit
So, next step is to track the wires and check continuity? Advise, please
 

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1992 W124 260E
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Discussion Starter #37
But forgot to check if Ground on engine side is OK or not.. Will do that tomorrow morning
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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2,299 Posts
Your O2 sensor and connectors could be different than mine. So I will not comment on the details.
The only thing that is evident is that the Green one is the actual sensor wire and is the one that should be not be at a steady voltage when the engine is warmed up and running and should cycle between 0.15V to 1V or so. You should measure between green and the chassis. You may also have a heater element connection/supply issue from your description.

You mentioned this is at 0.44V. If it is just steady and not cycling that means the system is not in working order at the moment.
 

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1992 W124 260E
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Discussion Starter #39
Your O2 sensor and connectors could be different than mine. So I will not comment on the details.
The only thing that is evident is that the Green one is the actual sensor wire and is the one that should be not be at a steady voltage when the engine is warmed up and running and should cycle between 0.15V to 1V or so. You should measure between green and the chassis. You may also have a heater element connection/supply issue from your description.

You mentioned this is at 0.44V. If it is just steady and not cycling that means the system is not in working order at the moment.
Ok, Green, positive and Chassis, negative... And engine in warm condition. Reading should be between 0.15 ~ 1V...will do this today
 

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Discussion Starter #40
Connected the Green to positive and negative to door jamb. This is what I got:

First 2 minutes: 0.4 increasing to 7.56 V
5" - 0.819 ~ 0.841 /750 rpm
10" - 0.875 ~ 0.884
15" - 0.875 ~ 0.888 /700 @ 1.5 oil
no shakes or stalling

AC ON
15" - 0.790 ~ 0.808 /700 rpm
20" - 0.798 ~ 0.818
25" - 0.809 ~ 0.823

Noticed that AC clutch not disengaging. Previously, it disengaged frequently. That's why I could read AC clutch off reading.

Switched off AC, clutch disengaged.

Switched AC on:
30" - 0.765 ~ 0.814
35" - 0.783 ~ 0.834 AC on but AC clutch didn't disengaged throughout the 5 minutes

35" - AC OFF clutch disengaged
0.838 ~ 0.855
40" - 0.869 ~ 0.882

Look forward to hearing back from dolucasi about the readings of the O2 sensor.

So, I now noticed that the AC clutch didn't turn on/off. It wasn't like this before. It used to turn on/off rather quickly... Did I touch anything? No.
 
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