EHA settings - PeachParts Mercedes-Benz Forum

just-n-time · #1 01-14-2007, 08:18 PM

Just-n-time here, today I spent time checking out the voltage on the eha and found it to be quite different than the settings I was told it should be at.
Settings on the digital meter 20 volts DC.
setting the meter in series with the brown wire black stripe at the EHA,I had
a reading of 4.25 cold after it began its warm up say 40C I had -7.43 and after
Eng.was warm it was -9.87 at 2000 it was 4.04 positive.
The allen screw was turned out 1/8th air mix was adjusted and the new readings were,3.89,I pulled the EHA again and turned the allen out 1/8th more
But the eng. would not restart I have moved the 3mm air mix up and down an can't get it to fire up it takes the cold start of fuel and runs till it is gone, but I cant find that spot to keep it running dose any one have any Idea of what I need to do?

1990 420sel

cool · #2 01-15-2007, 02:04 AM

whats your car? model series?

just-n-time · #3 01-15-2007, 11:13 AM

Quote:

Originally Posted by cool

whats your car? model series?

1990 420sel

300holst · #4 01-15-2007, 12:13 PM

I'm not familiar with the adjustment of the EHA (yet), However, you stated that you set the digital voltmeter to 20volts and connected it in series with one of the wires to the EHA. I believe you intended to measure the current flowing to the EHA and thus the meter should be set to a current scale (ma or A).

When the meter, set at volts is connected in series, it has a very high resistance and blocks the current to the EHA. If this is what is happening, the EHA will not be functioning and may explain your starting/ running problems.

just-n-time · #5 01-15-2007, 01:47 PM

Quote:

Originally Posted by 300holst

I'm not familiar with the adjustment of the EHA (yet), However, you stated that you set the digital voltmeter to 20volts and connected it in series with one of the wires to the EHA. I believe you intended to measure the current flowing to the EHA and thus the meter should be set to a current scale (ma or A).

When the meter, set at volts is connected in series, it has a very high resistance and blocks the current to the EHA. If this is what is happening, the EHA will not be functioning and may explain your starting/ running problems.

Well I went out and reset the meter to ma. and it sputters as if to stall so back to DC Volts and it is reading very well.
I dont know for sure but the turn ccw may have shut the fuel down to not enough to allow it to run,I went back into the EHA and turned the screw the half and one more making it a full turn cw and it started up.Then I reset the air mix to smoth it out I now have a reading of 6.2 @ x11 #3
and +9.69 at EHA. j-n-t

just-n-time · #6 01-15-2007, 02:51 PM

Quote:

Originally Posted by just-n-time

Well I went out and reset the meter to ma. and it sputters as if to stall so back to DC Volts and it is reading very well.
I dont know for sure but the turn ccw may have shut the fuel down to not enough to allow it to run,I went back into the EHA and turned the screw the half and one more making it a full turn cw and it started up.Then I reset the air mix to smooth it out I now have a reading of 6.2 @ x11 #3
and +9.69 at EHA. j-n-t

Ok,recap time,I reset the EHA,then got it to start,readjusted the air mix till a very smooth Idle tried the MA. settings again after pulling the ICV plug to get 2000 readings.it worked no sputter,these are the readings,hold on there,well
Warmed fully 80C
EHA idle -.00 to +.01
X11#3 10MA setting .2 to.5 slow rise and fall
EHA 2000 -.01 to +.08
X11#3 10MA setting .02 to.06 very slow rise and fall with a very long pause between movement.
Thats it how did I do?
next the potentiometer settings and more need for help thanks for the help.
j-n-t

garymand · #7 01-15-2007, 08:35 PM

"EHA idle -.00 to +.01" Wow, great right meter setting

"EHA 2000 -.01 to +.08" Again just about right

"X11#3 10MA setting .2 to.5 slow rise and fall" OOPS. Should be volts, about 7.0Volts

"X11#3 10MA setting .02 to.06 very slow rise and fall with a very long pause between movement." I'm surprised the meter in MA didn't short the signal and hurt something, Must be a well engineered test point. Someone must have told the designer a guy named JNT would hook a current meter up to measure volts.

"Thats it how did I do?" 50/50?

Do it again measuring the voltage at pin 3, Idle and 2000 for the 10% difference. Hopefully its close to 7V. At least, adjust it to get the 10%. Lets look around and ge the voltage right. The formula I saw was (1- (pin 3 / pin 4). ie., 7/13.8 = .5. 6/13.8=.43 1-.43=.56

just-n-time · #8 01-15-2007, 10:37 PM

Quote:

Originally Posted by garymand

"EHA idle -.00 to +.01" Wow, great right meter setting

"EHA 2000 -.01 to +.08" Again just about right

"X11#3 10MA setting .2 to.5 slow rise and fall" OOPS. Should be volts, about 7.0Volts

"X11#3 10MA setting .02 to.06 very slow rise and fall with a very long pause between movement." I'm surprised the meter in MA didn't short the signal and hurt something, Must be a well engineered test point. Someone must have told the designer a guy named JNT would hook a current meter up to measure volts.

"Thats it how did I do?" 50/50?

Do it again measuring the voltage at pin 3, Idle and 2000 for the 10% difference. Hopefully its close to 7V. At least, adjust it to get the 10%. Lets look around and ge the voltage right. The formula I saw was (1- (pin 3 / pin 4). ie., 7/13.8 = .5. 6/13.8=.43 1-.43=.56

Yes I will I may have done this my page of numbers is full of scratch marks looks like a chicken ran north south east and half way west, I have some reading here in volts DC @ 10 and it is 6 to I cant read the others so I will heat it up in the am and make sure of the job.j-n-t

just-n-time · #9 01-16-2007, 02:01 PM

Good morning, the new test took place and DC volts are as follows.
Idle p3 average of 4 to 5.4 = 4.7 .- 13.8= 66%
2000 5.2&5.8= 5.4 -. 13.8 =59.5%

reset mix got,
Idle 58%
2000 54%
So this means I am still high on my fuel pressure need to reset the EHA again?

just-n-time · #10 01-21-2007, 08:36 PM

Hi everyone,worked on the EHA today,I went back in and gave it a turn ccw 1/8th hit the spot. New reading Idle -0.00 to + 0.00 at 2000 I have the same reading. After resetting the air mixture we have Idle 7 to 8 in slow swing this is volt setting DC 10. 2000 rpm is a steady 6.2 volts this is 48 1/2% to 54% respectively.
Now on to the potentiometer, it is not responding to adjustment.after trying to get readings and I am not getting any thing like the numbers that have been posted. I tried to move the pot. and have no change in the Idle. I removed the pot and tried to get ohm readings, this is what I have,
1&3=4.5 ohm@ RX1K
1&2= INFINITY
2&3= INFINITY
pot arm and wiper 0

200K ko eo
1&3= -165.7
2&3= - 155.1
1&2= -39.6

ko e running
1&3= -166.1
2&3= -89.5 to-130.2
1&2= -78.6 to -80.3 this is again at 200k

DC volt 10
1&3=4.8v
2&3=3.2v
1&2=.7to.8v rapid fluctuation can any of the people who have worked this item give me some hints.jnt

garymand · #11 01-30-2007, 04:26 PM

Not in a great place to help, I think you said a new one is on the way. sounds good.

1--/\/\/\/\/\/\/\---2 A resistor is usually drawn kinda like this to represent a long wire resistor. The wiper is then a contact that moves along the wire. lets say pin 3.
Measuring between 1 and 2 will be a constant resistance.
Measuring from 3 to either 1 or 2 will give a number that changes as you turn the wiper.

You neede to measure with the connector off - no power. don't need to measure with volts connected.

Once you say you got 4.5 on the 1K scale so that is 4.5k ohms. And possible. but nothing between 1 & 3 nothing between the others, maybe measurement error. You should get a reading between any two - all pairs.

one pair never changes other two change.

And you say you got this I think with connector on and power on? how are you changing the wiper position?
DC volt 10 Good
1&3=4.8v Probably good this looks like the resistor
2&3=3.2v Should change as wiper moves
1&2=.7to.8v rapid fluctuation Good!! Tells me the wiper is #2 and it is at the bottom of travel maybe fluctuating with idle air movement?

Trouble is the 2,3 voltage should be fluctuating too, up at the 3.2V. I would expect the .7 to go higher toward the 3.2 as you raise the rpm.

I'm sorry, I don't know what moves the wiper. If you take it off I'm sure you will see a hole for a shaft or a shaft that goes into the air horn box. Find a way to rotate the wiper while measuring the resistance from 2 to 1.

I would expect it to go from 0 to 4.5k ohms and 2 to 3 to do the opposite.
It needs to be a smooth change, no skipping or jumps. Some one has posted pictures of the thing appart and it shows the wiper and the circular resistor made of carbon deposited on a ceramic substrate. His wiper had worn through the carbon resistor in under the wiper so he just bent the arm of the wiper to move the wiper over to good resistor and it worked. (for a while not a ling term fix)

Gary

just-n-time · #12 01-31-2007, 12:43 AM

Hi Gary, glad your back, The new pot. came in today I will not have time to do much for the next few days, have to keep a couple of date's I can't get out of.But as soon as I can I will take several readings from the new unit before I put it on,and after it is on, will keep you advised as to condition of the car, as for now it is much better in the fuel department,just a little rough idle and search on deceleration,and when you first start the car it stutters for a second be for going on to reasonable but not great idle.jnt

Oracle12345 · #13 04-16-2009, 01:49 PM

how are you guys measuring current at the eha in series?

dpetryk · #14 04-17-2009, 06:47 AM

Current measurements are taken in series.

tinypanzer · #15 04-17-2009, 10:46 PM

Me thinks you need to brush up on using a meter.

1) For voltage measurements, you connect the meter in parallel to the circuit. Hooking it up in series will add the internal resistance of the meter to the circuit, and will drastically change your readings.

2) For current measurements, you connect the meter in series. If you hook it up in parallel, the meter's low internal resistance (in this setting) will probably short circuit your car and blow a fuse or worse.