M103 EHA/Lambda Adjustment HELP
 

I think I've narrowed down the problem to either the EHA or Lambda adjustment (or both). I unplugged the EHA and the car ran GREAT...no hesitation, power, exhaust didn't smell so strong. Friend helped me test the Voltage to the #3 pin. With the EHA unplugged the reading was 1.7. With the EHA plugged it read 6.9. I tried adjusting the lambda both ways (push down, turn) and it didn't change the reading at all.

The 02 sensor is new, and I've replaced every sensor I can tell MIGHT have something to do with this. In the next couple of days I'm getting a meter that does duty cycle.

Does this sound like the EHA out? I'm more than willing to replace it if this hesitation will STOP...

Thanks for ANY ideas!!!

Robert,

I remembered to put the meter in the car last night. Measuring the DC voltage at pin #3 will not give you a meaningful indication. It needs to be set for 50% duty cycle.

You need to read the Steve Brotherton article about this in the DIY and maybe do a search on lambda adjustment. There was a good thread about this by Donnie a couple of years ago.

I have a customer in house today and will probably be out to lunch with her, but let me know when you would like to pick up the meter and I will try to have it ready for you.

Good luck,

TCCBass:

Sears sells a very affordable and competent digital multimeter for $30 WITH duty cycle. You need to measure the mA coming from the EHA if you find that your duty cycle is fluctuating wildly (beyond the allowable 10-15%).
If after you check your duty cycle and it fluctuates wildly you'll then need to check the mA coming from the EHA using a MB harness tool -- which I have and you're welcome to borrow it. (please email me and I'll be happy to mail it out to you)

If the EHA is not giving out the proper mA, this still doesn't mean your EHA is bad .... it could be due to improper lower chamber pressure in the fuel regulator, or a short circuit somewhere between the ECU and your EHA.

Good luck with your diagnosis... ;)

I have one of the $30 duty cycle DMM's from Sears. Actually it was $27 because I accidentally bought it on a 10% off Craftsmen Tools day.

I understand, though, that they no longer offer that meter. This is the one that TCCBass is borrowing from me.

As for the EHA harness, where did you get it? Would it be difficult to make?

Have a great day,

Here it is. I found it at Sears.com under: Craftsmen Tools/Electrical Items/Other


Sears Item #03482040000
Mfr. Model #53338


Inflation has hit, however, it is $39.99 on that site. That is still a great bargain. It wasn't long ago when the lowest price you could find for ANY DMM was over $100. This is a very good little meter.


Have a great day,

Larry,

I bought the harness from a MB dealer. Cost was $15. It would be tough for me to make, for others more electronically inclined, I doubt it. It's on loan if anyone needs it.

http://www.members.aol.com/lawnetpfm/harness.jpg

Paul,

Sorry to be a pest about this. Do you have a part number?

Thanks and have a great day,

Not a problem Larry. p/n is 102 589 04 63 00 07. On how to use it, here's a blurb from a previous post.

Good luck..

Paul, what was the verdict on your EHA. Did you ever figure out what the problem was?

Not yet Stephen :o

I really haven't had time, and the engine runs flawlessly with only a minor drop in MPG it seems, so for now, until I get more time I'll let it be.

I do have 2 new screw seals that I forgot about. Think I'll put those on and see if that solves the problem. I also need to connect that vacuum line at the base of regulator :D.

I guess one advantage of having this fuel problem and not driving the car is that it is getting to be a LOW mileage car. It's been sitting a lot. 1K miles in about 3-4 months.

I will get the meter from Larry hopefully today. I have to be up in that part of the city this afternoon.

Thanks for all the instructions...I may go to the dealer and buy one of those harnesses this afternoon. I REALLY appreciate the instructions on checking the EHA and the lambda. I drove it this morning with the EHA powered. It is driving better than it did before I started all this, but it's apparant that it's running quite rich.

Paul, you spoke of the vehicle's harness. I know where the plug is for the EHA, but where is the other harness? Will it be apparant when I start fishing around under there? Also, I assume I use the extra plug shown for testing?

I'll post results this evening. I'm ready to put some miles on this car (and get more than 10-12 MPG)!

Robert,

While I'm thinking about it, make sure you change the oil and filter as soon as you correct the rich condition. Your oil is being dilluted with fuel in this situation, not a good thing.

Have a great day,

Larry,

I'm due for an oil change...so it will get one as SOON as this issue is resolved.

Thanks for your help!

Unplug the connector from the EHA. The harness then plugs into the EHA, second connector plugs into the wire you just disconnected from EHA, and third is for testing.

You'll figure it out, none of the 3 connectors are the same.

Also this part (tool) normally isn't stocked at MB dealers. They probably will have to order it for you. :(

Good luck..

SUCCESS I think! I got the meter from Larry Bible. Tested it when I got home. Was registering at 82-84%. Got it calmed down to around 45, drove it for a bit, and adjusted it to where it ranges from 49-55% A/C off and 45-51 A/C on. I'm pleased with that for right now. It seems to fluctuate and not stay at all steady, but if it averages those I'm pleased. It perhaps could be time for a new idle valve (it's been cleaned thoroughly) but overall...after I removed the resistor for timing and with this adjustment the car runs like it did before I bought it. Needless to say I'm VERY pleased. I'll knock on some Zebrano that it stays that way!

Thanks for ALL the help...I'm once again a satisfied 124 owner!:)

Robert,

Congrats on a job well done. It sounds like you're ready for the ASE test!

Have a great day,

You lost me there, can you elaborate on that comment?:confused:

Capt...

I removed the little resistor that's attached to the A/C line. It's the one that compensates for lower octane fuel. I use ONLY 92 octane, so I removed it.

The car is driving SO well. I can pull out without fear now.

Cap'n,

Robert is referring to the ignition advance resistor that is discussed to death in the Performance Paddock.

The long and short of it is; there is a resistor ty wrapped to the a/c line near the master cylinder. When you remove it, you add 6 degrees ignition advance. On Euro cars there is a rotary switch that allows adjustment for varying octanes. On the US cars, this resistor retards the maximum ignition advance for emmissions reasons.

There is no real downside to removing it because these engines have a knock sensor that prevents preignition problems.

My $0.02,

I've been meaning to mention this with every post I've made in this thread and continue to forget.

If you don't have a duty cycle meter, but you DO have an old dwell meter, you can substitute the dwell meter for the duty cycle meter when setting the lambda adjustment. You simply look for mid scale on the dwell meter. All a dwell meter is, is a duty cycle meter marked up in degrees instead of %.

Have a great day,

Thanks Larry!
 

I had gone back in a search and found that info. On the dwell meter subject.. What numerical readings would you look for on the scale, 45-55 degrees? I have an old Sun dwell meter, let's see... I loaned to my friend Clark back in 1984 I think! :D

You will be looking for half scale which is 50% duty cycle. For example. For a four cylinder, max scale will be 90 degrees. This means that 45 degrees on the four cylinder scale will be 50% duty cycle.

I actually dug out an old Dwell meter and experimented with it. It was reading exactly center scale on my 300E pin 3. I didn't know whether or not to trust it at the time, so I bought the $27 meter. It confirmed that my lambda was set at 50%. This gave me confidence in using the dwell meter, but now I had the duty cycle meter so I didn't need it.

Hope this helps,