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You’re welcome! … half of the thanks I passed on to my wife, who called me several times for the Sunday lunch and waited for me until I had finished it. :)

Thanks for the appreciation!
 

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Today I reread my procedure for the EHA check / adjustment (post 57) and edited it. Regrettably there was a mistake in it regarding the terms “clockwise” and “counterclockwise” in step 3, which I have corrected today.
I’m sorry for that and I hope it hasn't caused any confusion!
H.D.
 

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Well I'm glad you got that taken care of H.D. I was confused as hell!!!!

Really, thanks for taking the time to reread your excellent post, realize the error and correct it.. You can't ask for more than that.

I'll be adding it to our DIY section this week.

Jim
 

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Q. about the 2.5K ohm axial-lead resistor for replicating temp sensor resistance when testing differential pressure:

How many Watts should the resistor be calibrated for?? I mean, I found resistors handling no more than 0.25 Watts and some can take 10 Watts..

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12 volts into 2.5k ohms is about 0.005 amps, or 5 milliamps. 12 volts * 5 milliamps is 0.06 watts.... in reality, there's /less/ than 12 volts across that resistor, even a 1/10th watt resistor would be fine, but yeah, use the 1/4 watt, thats plenty.


btw, this is simply ohms and watts law.

ohms law is, volts/ohms = amps, or ohms * amps = volts, or volts / amps = ohms, all three are the same formula algebraically. usually 2 of these terms are constant in a given circuit, so you can always calculate the third.

watts law says volts * amps = watts. therefore, watts/volts = amps, or watts/amps = volts. combining these formulas, you come up with things like volts*volts/ohms = watts.

knowing these two formulas, and some simple rules for series and parallel resistances, and you can figure out what most any circult is doing.
 

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12 volts into 2.5k ohms is about 0.005 amps, or 5 milliamps. 12 volts * 5 milliamps is 0.06 watts.... in reality, there's /less/ than 12 volts across that resistor, even a 1/10th watt resistor would be fine, but yeah, use the 1/4 watt, thats plenty.
Haven't found a just the 2.5K resistor yet, 2.2K and 2.7K are the closest. Do you happen to know if one of those is in the same "temp" range as the 2.5K
 

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s/b close enough, I'd think. we're talking about b11/2, the 4-pin coolant temp sensor for both KE and EZL ? at +20C, the book says "2.28-2.72 kOhm", and at 80C, its 290-364 ohms. so a higher resistance == colder.
 

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Ok. Thanks. Yup, to replicate the 4 pin coolant sensor when testing fuel differential pressure and adjusting EHA. Replaced a leaky EHA in January with undetected air leaks in the rubber boot. Had to enrichen the new EHA way over half a turn just not to fry my cats. Was so lean the exhaust smelled rotten eggs. Adjusted the EHA so the engine run ok without ECU. Didn't have multimeter at all. Now I've replaced all rubber + potentiometer cleaned up air meter, thr.body and the manifoild oil pool and about to tune the EHA back correctly.
So both res is just in range. I'll maybe going for the "coldest" one then to be sure the ECU reads cold engine.

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In his DIY, H.D. states the duty cycle is supposed to be 50% fluct. and he suggests a final setting at 47% fluct. But in the A/F mixture DIY thread a post is refering to WIS data which says 40% at idle for CIS-E. And that it is only older CIS without EHA which is supposed to have 50% fluct. This is contradicting.
What actually is the correct idle duty cycle for a 1991 M103-3.0 (EGR-less German edition) ??

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Shoot for the 47%. Remember, only adjust after the car is at full operation temperature.

Good luck

Jayare
 

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In his DIY, H.D. states the duty cycle is supposed to be 50% fluct. and he suggests a final setting at 47% fluct. But in the A/F mixture DIY thread a post is refering to WIS data which says 40% at idle for CIS-E. And that it is only older CIS without EHA which is supposed to have 50% fluct. This is contradicting.
What actually is the correct idle duty cycle for a 1991 M103-3.0 (EGR-less German edition) ??

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Depends who you talk to, really. Clark who used to be a member here and a certified MB tech since the early 80's said that they set the duty cycle @45% on the 124's when they were new. It's so easy to change;run it for a month @45% and then run it for a month @48%. Choose which you like for acceleration & gas economy.

I run about 48%, but I have an aging, funky air-flow potentiometer.

Kevin
 

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OK. BTW, are the DC numbers the same for all M103 editions and all nations? Euro/Ger/UK/US/AUS etc.. I understand California cars has special emission requierments and some cars has EGR and air pumps..
 

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All 103 US models had the air pump and EGR. Can only speak to them. The "California" models had a code blink function built in(push button) that allows you to pull emissions codes. I suspect the DC #'s could vary a bit without the air pump and EGR. Don't some Euro cars have a retard/advance button dial you can tweak for different gas situations?

Kevin
 

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There is one particular sentence I’d like to change in post 57, but it seems that it can not be edited anymore.

In step 2) I said:
‘Then the meter should read 0 mA, fluctuating with up to +/- 3 mA both at idle and at 2000 rpm.’

I should have said:
‘Then the meter should show fluctuating current within the range of 0 +/- 3 mA both at idle and at 2000 rpm.’

At idle - with the duty cycle adjusted to fluctuating around a mean value of 50% - the EHA’s baffle plate oscillates around its currentless rest position, which should be confirmed by an EHA current fluctuating around a mean value of ‘0’ milliamps. And like the duty cycle, it will (usually) be different at 2000 rpm, but it should still be within the range of –3 to +3 milliamps. It being beyond that range calls for EHA adjustment, IF any other possible reason is ruled out!
A possible other reason for a too big (EHA current / duty cycle) difference between the two revs could for instance be a false air leak, maybe a hole in the rubber boot between the air flow meter and the throttle valve, especially if it’s a hole that’s further opened with higher revs (due to higher vacuum). That would lead the ECU to enrich the mixture by sending excessively more possitive current through the EHA’s coil (leading to an excessively higher duty cycle) at the higher rev.

The (fluctuating) duty cycle is actually just an easier to check representative of the EHA current, with the additional option of (static) error codes. The range of the fluctuating EHA current, which is generated based on the o2-sensor’s input to the ECU, determines the ECU’s square wave voltage output to the diagnostic socket, where it can be measured in 'duty cycle', 'dwell angle' or 'volt'.

Regarding the question about the most proper duty cycle:
With an otherwise healthy system, the best running behavior is given with the EHA slightly further opened at idle, which is effected by a current fluctuating around a mean value below ‘0’ milliamps, which is accompanied by a duty cycle fluctuating around a mean value below 50%. … How much below 50% depends on how healthy the system (not only the injection system) is. It can be in such a bad condition that the best running behavior is given with a duty cycle way above 50%.

H.D.
 

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Yes. The Euros has a dial which regulates the timing after fuel quality. I'll asume this is a "global feature" with fuel qualities of especially the 3.world in mind and the exception are the US and maybe Aus(?) and UK(?) The normal setting is S (Super) for 95 octane and it can be dialed down for lesser qualities and octanes

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There is one particular sentence I’d like to change in post 57, but it seems that it can not be edited anymore.

In step 2) I said:
‘Then the meter should read 0 mA, fluctuating with up to +/- 3 mA both at idle and at 2000 rpm.’

I should have said:
‘Then the meter should show fluctuating current within the range of 0 +/- 3 mA both at idle and at 2000 rpm.’

At idle - with the duty cycle adjusted to fluctuating around a mean value of 50% - the EHA’s baffle plate oscillates around its currentless rest position, which should be confirmed by an EHA current fluctuating around a mean value of ‘0’ milliamps. And like the duty cycle, it will (usually) be different at 2000 rpm, but it should still be within the range of –3 to +3 milliamps. It being beyond that range calls for EHA adjustment, IF any other possible reason is ruled out!
A possible other reason for a too big (EHA current / duty cycle) difference between the two revs could for instance be a false air leak, maybe a hole in the rubber boot between the air flow meter and the throttle valve, especially if it’s a hole that’s further opened with higher revs (due to higher vacuum). That would lead the ECU to enrich the mixture by sending excessively more possitive current through the EHA’s coil (leading to an excessively higher duty cycle) at the higher rev.

The (fluctuating) duty cycle is actually just an easier to check representative of the EHA current, with the additional option of (static) error codes. The range of the fluctuating EHA current, which is generated based on the o2-sensor’s input to the ECU, determines the ECU’s square wave voltage output to the diagnostic socket, where it can be measured in 'duty cycle', 'dwell angle' or 'volt'.

Regarding the question about the most proper duty cycle:
With an otherwise healthy system, the best running behavior is given with the EHA slightly further opened at idle, which is effected by a current fluctuating around a mean value below ‘0’ milliamps, which is accompanied by a duty cycle fluctuating around a mean value below 50%. … How much below 50% depends on how healthy the system (not only the injection system) is. It can be in such a bad condition that the best running behavior is given with a duty cycle way above 50%.

H.D.
This is really good stuff, H.D. Thank you.
 

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Great information

There is one particular sentence I’d like to change in post 57, but it seems that it can not be edited anymore.

In step 2) I said:
‘Then the meter should read 0 mA, fluctuating with up to +/- 3 mA both at idle and at 2000 rpm.’

I should have said:
‘Then the meter should show fluctuating current within the range of 0 +/- 3 mA both at idle and at 2000 rpm.’

At idle - with the duty cycle adjusted to fluctuating around a mean value of 50% - the EHA’s baffle plate oscillates around its currentless rest position, which should be confirmed by an EHA current fluctuating around a mean value of ‘0’ milliamps. And like the duty cycle, it will (usually) be different at 2000 rpm, but it should still be within the range of –3 to +3 milliamps. It being beyond that range calls for EHA adjustment, IF any other possible reason is ruled out!
A possible other reason for a too big (EHA current / duty cycle) difference between the two revs could for instance be a false air leak, maybe a hole in the rubber boot between the air flow meter and the throttle valve, especially if it’s a hole that’s further opened with higher revs (due to higher vacuum). That would lead the ECU to enrich the mixture by sending excessively more possitive current through the EHA’s coil (leading to an excessively higher duty cycle) at the higher rev.

The (fluctuating) duty cycle is actually just an easier to check representative of the EHA current, with the additional option of (static) error codes. The range of the fluctuating EHA current, which is generated based on the o2-sensor’s input to the ECU, determines the ECU’s square wave voltage output to the diagnostic socket, where it can be measured in 'duty cycle', 'dwell angle' or 'volt'.

Regarding the question about the most proper duty cycle:
With an otherwise healthy system, the best running behavior is given with the EHA slightly further opened at idle, which is effected by a current fluctuating around a mean value below ‘0’ milliamps, which is accompanied by a duty cycle fluctuating around a mean value below 50%. … How much below 50% depends on how healthy the system (not only the injection system) is. It can be in such a bad condition that the best running behavior is given with a duty cycle way above 50%.

H.D.
I must say very impressive !!
 
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