None of the readings are correct , or even close...but I think it is the meter or your use.

The chart is listed is in OHMS .

So, go back to that first range. I believe you have been reading in K ohms.

Here is what you are looking for :

20C -2500
80-325
90-245
100- 185

Diag across...both Thermistors are the same value .. [ or should be]

Use the same setting you used for the CPS reading ..that will be the single OHM range on that meter ..
Some meter have a seperate Rx1 range..I do not see it in that meter.. [ Manual will have that info]

OR,


Go get a 100 ohm resistor @ RS and measure that KNOWN value with the meter....then you know if the meter or your setting is wrong.

I think you are on K ohms....cuz it's a cheapo meter...guys like you should buy Auto-Ranging meters....they are in-expensive and you don't have to know Range Switching .

As a side note, before starting the car when you know the condition is going to exist, turn the key On/Off for a couple of secs, two time before cranking..that will assire fuel pressure is up before start..if that remedies the condition, you have a fuel supply issue. The FP comes on for a sec at each key ON cycle. And that sig comes from OVP , thru ECU. [ which is why OVP was one of the suspect/ suggestions]
Try that test.

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A Dalton

It is a cheapo meter, and I am in K ohs, as when I have the meter set to the 200 scale I get no reading. The readings I noted are with it set to the 2K range. However, it seems like it's just a decimal point issue. I found this chart of values in the archives and it seems to match up with what I'm seeing pretty well:

Temperature °C/°F - Resistance kO
-20/-4..............15.7
-10/14...............9.2
0/32..................5.9
10/50.................3.7
20/68.................2.5
30/86.................1.7
40/104...............1.18
50/122...............0.84
60/140...............0.60
70/158..............0.435
80/176..............0.325
90/194..............0.247

Phil got the new sensor to me overnight at a very resonable $10 shipping rate. It's 78F/25.55C in the shop this morning and the new sensor measures 1.86 so that seems to match up to the above chart pretty well.

My wife has the car 'til late this afternoon. When it gets back I'll try the fuel pressure test.

__________________
2000 Mercedes S500
1990 Mercedes 560SEL
1970 Triumph Spitfire

Same chart ..I just cut it to the ones we test on the higher range ..they are the critical readings and confirm the sensors running values.
You want to use coolant temp gauge of car for comparison.

That can also be checked by using a 38 ohm resistor in place of that sensor...that will read exactly 100C if gauge is within spec. calibration.

The K ohms is why the decimal is threee off [ meaning K ohms reading]...

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A Dalton

i can think of one item that has not been replaced the fuel regulator that may effect running.

The fuel pump Relay will be on its last stages at this time along with the OVP .
replacement of the fuel relay will assure future reliability as i found out.

mak
89 300SE

As a side note, before starting the car when you know the condition is going to exist, turn the key On/Off for a couple of secs, two time before cranking..that will assire fuel pressure is up before start..if that remedies the condition, you have a fuel supply issue. The FP comes on for a sec at each key ON cycle. And that sig comes from OVP , thru ECU. [ which is why OVP was one of the suspect/ suggestions]
Try that test.
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A Dalton

Turning the key on/off for a couple of seconds made no difference.

I'm going to replace the coolant temp sensor, even though the one I have seems to test OK. I bought it, so I'd just as well put it in. Hopefully the one that's in there now has something going on that comes and goes.

Does anyone know what size socket I need, I don't have one big enough.

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2000 Mercedes S500
1990 Mercedes 560SEL
1970 Triumph Spitfire

I'm going to Sears today to find the right size socket so I can replace the coolant temp sensor.

Last night I installed the "new" airflow potentiometer. When I took it out of its package it didn't look new, though the carbon tracks did. Perhaps it's "remanufactured." Unfortunately I couldn't get it to adjust correctly. Rotating it as far CW as I could gave a reading of 1.35v + or -, nowhere near the .70v +/- .101v called for. Rotating it CCW gave even higher reading, over 2. I tried to drive it that way but it was really bad. Hard to start, stalled every time I came to a stop, the CEL came on and it smelled like it was running very rich.

Thinking the difficultly in adjusting it might have something to do with my turning the adjustment screw on the EHA 1/4 turn CW a couple of days ago, I turned the EHA back to where it was. Unfortunately this made the car run even worse and did not help in getting the AFP adjusted correctly.

I gave up and replaced the "new" airflow potentiometer with the original, was able to adjust it into spec quite easily, and the car ran fine again. By now it was past midnight and I was too tired to let it cool down a bit to see if it did its start/stall thing.

However, in order to have something to look forward to this morning, I removed the EHA and adjusted it 1/2 turn CW from where it was when I bought the car. When I turned it 1/4 turn CW earlier it did seem to help a little.

This morning it started on the first try with no sign of the start/stall problem I've been chasing so long. I let it sit about an hour, and the second start was also perfect. Fired right up, idled smoothly, ran perfectly. I let it sit about 2 hours more and it started on the first try, but did stumble slightly before settling down to a smooth idle.

I let it sit another hour and this time it took 2 try's to get it going. On the first try it started then instantly stalled; but, the on the second try it fired right up and settled to a smooth idle without stumbling.

Am I onto something here with the EHA? Should I just drive it for a few days to see what happens before trying anything else, or should I try turning the EHA adjustment a little more CW?

BTW: I see Sears has a Craftsman auto-ranging meter on sale for $20. I'll pick one of those up to go along with my new socket.

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2000 Mercedes S500
1990 Mercedes 560SEL
1970 Triumph Spitfire

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Great little meter.

make sure it has Duty/Htz..

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A Dalton

I called them, it does. Any advise re: my messing about with the EHA, and it being the source of my start/stall problem?

From what I understand, I'll probably need to adjust the mixture after doing so. I found the instructions in the archives, so I'll check it as soon as I get home with the new meter.

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2000 Mercedes S500
1990 Mercedes 560SEL
1970 Triumph Spitfire

It's a 22mm. Get a deep socket, thin wall. As thin as you can get it at least. Otherwise you might not be able to squeeze it between the valve cover.

I bought the thinnest Craftsman 22mm deep well socket (thanks Chowbow) I could find, and a new Craftsman model 82351 auto-ranging digital multimeter.

It was late when we got back and the engine was pretty hot, but I still wanted to fire up the new multimeter to see what duty cycle reading I'd get. I figured I'd be off since I turned the EHA adjustment CW (rich) 1/2 turn, But I was pretty surprised to see a reading of 99.9 to 100.0% with the red in #3 and the black in #2! Especially since the car is running very good, even the start/stall situation seems better since I adjusted the EHA, not perfect but much improved.

Does this duty cycle number make any sense, or is it more "operator error" in using the meter?

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2000 Mercedes S500
1990 Mercedes 560SEL
1970 Triumph Spitfire

Duty cycle should be around 45% to 50%.

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Allen Kroliczek
Oak Grove Autosport | Oak Grove Autosport
01 G500, 82 300TD, quite a few more.....

Was the percentage jumping around constantly? It should basically be jumping around all the time. I had a 69.9% constant reading for a while, and it was because I had an engine code triggered. Cleared the code and my duty cycle was reading fine after that.

Yes..on some versions, you have to have codes cleared and only then will the ECU output switch over to the on/off ratio mode.

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A Dalton

I went out this morning and took a reading with the key on/engine off. It was 14.9% with red-#3/black #2 & 85%, red-#2/black #3, so it looks like I have a California emmissions car. I know the archives have plenty of info regarding duty cycle so I'll work through that, then report back on where things stand.

At this point the only thing that has made a positive difference in the start/stall behavior is turning the EHA adjustment 1/4 turn CW (a little better), then a additional 1/4 turn CW for a total of 1/2 turn CW (better still). I have lots of new parts though! Undoubtedly a good thing as I bought the car with no records. Maybe that's why I was able to find such a nice one at such a low price.

The new meter is also great! Thanks for that suggestion Aurthur.

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2000 Mercedes S500
1990 Mercedes 560SEL
1970 Triumph Spitfire

intutive diagnosis suggest a replacement of the fuel pump relaay or resoldering its pcb.
mak
89 300se