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IIRC there is a brass screw that reveals the adjustment screw once its removed. In the infantile wisdom of the designers at Botsch the adjustment screw can only be accessed after the EHA is removed from the FD.
Yes there is a brass screw. And yes it could be adjusted without a pressure test/gauges, but you could also walk all the way around the barn instead of walking straight through it.

If we're gonna stick here with the same EHA that requires 'tapping' to make it work, just assume it's a bad, un-serviceable unit.

Kevin
 

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They make the adjustment screw difficult to access...because you're not really supposed to adjust it. If the EHA is bad, it should be replaced as it has been stated in the thread already its supposed to be flow matched to the distributor. If it were easy to access, every idiot would start making adjustments while ignoring more common places to look such as poor flow rates from the pump, bad filters, vacuum leaks, old ignition components...the list goes on.

In the real world, its worth adjusting it -- however in your situation it sounds like the magnet and internals are getting jammed. You could try soaking it in vinegar overnight and see if that helps, but be prepared to replace it regardless with a NEW unit.
 

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its that way because its meant to be tamperproof. its likely calibrated once in the factory, on a test jig, then assembled, and never touched again. until it breaks and has to be replaced.
 

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"Sticky EHA"

Thanks for all the feed back. My mechanic has a trick or two remaining before I buy a new walve:smile
This engine is a Hell of a lot more complicated than a Flat head Merc or a 283 Chevy small block:grin

Thanks again and when this problem goes away I'll post the fix.
 

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...be prepared to replace it regardless with a NEW unit.
Exactly, and new = brand new OE MB or Bosch in the box, not "just like new", refurb'd, reman'd, reconditioned, rejuvinated, recommissioned, "pulled from a working car", "just picked one up at the local yard", spit & polished, "tapped till it worked", "known to be good", yada, yada, yada
 

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Exactly, and new = brand new OE MB or Bosch in the box, not "just like new", refurb'd, reman'd, reconditioned, rejuvinated, recommissioned, "pulled from a working car", "just picked one up at the local yard", spit & polished, "tapped till it worked", "known to be good", yada, yada, yada

Just going down the "re-cycle" yard road. Passenger side view mirror1983 300CDTubo. Chrome is 98% motor is "tits" Batter up!:devil
 

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If you're going to go on a seek and find mission for a good EHA in the yard, be prepared to make a lot of trips and spend some gas money.

IMO, just not worth f'ing around with. Ask forum member lowesguy, who did a similar thing by purchasing a handful or so EHA units through eBay. The end results was they were all bad, and even he ended up going with new. Some people need to learn the hard way.
 

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Hi, Mercedes Fans

I have a 300 SL R107 with the M103 KE engine Year 1986 and a 300 CE-24 C124 with the M104 KE engine Year 1990.

Last week I could smell the gasoline under the hood on my C124.
I removed the Airfilter and I had a look at the LMM and the Fuel Distributor. The EHA was wet and I saw the gasoline coming out of the small holes.
At the Mercedes Dealer I bought a new EHA A0000703962, BOSCH No 2437020007 for 244 Euro.
The Srews and O-rings where provided too. I changed the EHA after removing the fuelpressure.
After I finished the engine was startet and no more smell. According to the WIS, there is no adjustment nessessary after replacement at the M104 engine.
The EHA A 000 070 3962 fits to all engines M102, M103, M104, M116 and M117 with the KE.

Best regards from Germany
Marcel


this is the old EHA and the 2 o-rings witch are 25 years old!
 

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I could smell the gasoline under the hood on my C124.


According to the WIS, there is no adjustment nessessary after replacement at the M104 engine.
I did this too about 7 years ago on my M104. Same result: no adjustment, no problem.

Also, the replacement EHA was used and from an M103 engine.

RayH
 

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... its likely calibrated once in the factory, on a test jig, then assembled, and never touched again. until it breaks and has to be replaced.
Which is why touching this adjustment srew often does become an issue after EHA replacement.

Every time I replace an EHA I check the duty cycle and the EHA current, and usually also the pressure difference between the upper and the lower chamber of the differential pressure valves. And often it proves necessary or at least reasonable to adapt the new EHA to the old fuel distributor.
In those cases I usually do that by means of the EHA current (not by means of the pressure difference). Only after I finished the adjustment according to the current, I often finally check the pressure difference of the differential pressure valves, which almost always proves correct then.
That's usually a process of repeated disassembly – adjustment – reassembly – test, which you should not approach when you are pressed for time.
 

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... After I finished the engine was startet and no more smell. According to the WIS, there is no adjustment nessessary after replacement at the M104 engine. ...
I would at least check and if necessary adjust the duty cycle and also check the EHA current.

And all the more I would do that after installing a used EHA, like rayhennig did.
 

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I would at least check and if necessary adjust the duty cycle and also check the EHA current.

And all the more I would do that after installing a used EHA, like rayhennig did.
In fact, it was someone else that said it but, yes, I also did check the duty cycle. You should check this after any replacements, such as the O2 sensor.

RayH
 

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the EHA current test is important, too.

the CIS-E control unit reads the O2 sensor, and uses the EHA to fine tune the mixture to maintain proper lambda. when everything is operating normally, you want to make sure that the EHA is in the middle of its control range when the O2 sensor reading is 50%, which indicates the engine is balanced. if the EHA is near either extreme of its range, then it will have trouble maintaining the proper lambda under the full set of operating conditions.

grr, i'm having trouble finding the EHA adjustment procedure in the service manuals. I think its in here, but this is a whole lotta complex stuff.
http://new.freescruz.com/.priv/W124/w124CD1/Program/Engine/103/07.3-0121.pdf
 

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Exactly! ... Basically adjusting the KE-Jetronic to the correct duty cycle is only half the job. … It should always be followed by checking the EHA current.

As volvo745 mentions – the EHA should operate around the middle of its control range, which is also its currentless rest position. There the EHA works most effectively. It’s the range where it has it’s highest dosage accuracy, which is good for the engines running behavior and it’s fuel consumption.
That is the key aspect of the adjustment of the "KE-Jetronic-Grundeinstellung" ("KE-Jetronic basic setting" or "duty cycle adjustment" - as you guys usually call it).
And if you install a new or a used EHA on an old fuel distributor, quite some luck is necessary if you expect it to work within that optimal operation range without adjustment.

Generally the EHA current check provides information about the overall health of the whole system. If the mechanical condition of the fuel distributor, including the EHA is good and all other involved components work well, the EHA’s amperage around zero amps (within +/- 3 milliamps) at idle coincides with a duty cycle of 50%.

Don’t worry about finding EHA adjustment procedures, volvo745 … I’ll prepare easy to understand instructions.
 

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EHA adjustments

HD I'd like to see your adjustment procedure as I'm not totaly sold on buying a new $300.00 part.












































as you or another listed, how does one determine if the strings, valve and other internals are broken. I was forced to use my 300 TE with the intermittent starting problem, so I started the engine 3-4 times and let it site for a few minutes without problem. Put the air cleaner back on and started the car and completed my errands without incident.?? Thecar ran strong thru the gears at in town/Highway speeds.
 

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I'll prepare something, but give me some time for that please. … That only makes sense, if several details are considered in it in order to lead to a good result (beginning with the duty cycle check / adjustment, the EHA current check, the actual hydraulic adjustment of the EHA and the differential pressure check).

Anyway – the EHA adjustment should not be taken lightly … it requires carefulness, patience and cleanness … not every MB mechanic dares to touch that.
 

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EHA check / adjustment

As announced you see below my procedure for the EHA check / adjustment. Sorry for keeping you waiting … I thought I better make sure it’s as detailed as the job demands.

Your intermittent problem (car not starting), which disapears by tapping on the EHA might not be solved by adjusting the EHA. When the engine starts (for instance after tapping the EHA) you may be able to check and if necessary adjust the EHA, but that doesn’t necessarily mean that after you’ve done that you will not have to tap it anymore to get the engine started.

Please read the last sentence of my last post once again! And if you’re sure you want to do this, pls follow the procedure precisely.

It consists of 4 steps:
1) Duty cycle check / adjustment
2) EHA current check
3) Mechanical / hydraulic adjustment of the EHA
4) Differential pressure check

Minimum hardware requirements:
  • Multimeter (best analog for reading fluctuating values) for voltage, amperage, duty cycle.
  • Rev meter (or a second person as an assistant).
  • Manometer (100 psi range, fuel resistant).
  • Short piece of hose (fuel and pressure resistant), which fits on both the manometer and the fitting on the fuel distributor, to which the cold start valve line is connected.
  • 2 hose clamps.
  • Straight pipe fitting with metric “M8 x 1” srew in thred, onto which the manometer hose fits.
  • 2.5 kΩ axial lead resistor.
  • New EHA o-rings.
Preconditions:
  • All other CIS and ignition system components should work properly, especially the o2 sensor should be in good condition and there should be no false air getting into the intake system!
  • Correct ignition timing.
  • Correct zero position of air sensor plate.
  • Throttle valve in contact with it’s idle stop position.
  • Correct adjustment of throttle linkage (including idle stop and micro switch activation).
  • Engine speed at 2500 rpm must fluctuate when the micro switch is manually activated.
  • Off-load battery voltage: 12.2 – 12.6 V.
  • With engine switched off and the key in “ignition on” position:
    - duty cycle with air sensor plate in zero position: 70% (California version, IIRC: 85%)
    - duty cycle with air sensor plate deflected: 10%
    - duty cycle with throttle valve fully opened: 20%
  • The vacuum line between the throttle valve and the regeneration valve of the fuel evaporation system must be pulled off at the regeneration valve and blocked.
  • The air filter must be installed and clean.
  • The engine must be at its normal operating temperature.

1) duty cycle check / adjustment:

I presume it’s known, but I’d like to mention it anyway:
I suggest to turn the adjustment srew in small increments (about 10°). To lower the duty cycle turn it clockwise, respectively turn it counterclockwise to raise the duty cycle. After each turn let the system settle for about 10 seconds before you take readings!
And record the total angle change of the adjustment screw! … turned to far the engine will stall … and you may not get it started again if you forgot how far and to which direction you have turned it the adjustment srew … then you’re screwed! … unless you know how to set a completely misalligned KE-Jetronic back to where the engine would start again (which is not too difficult).

Adjust the duty cycle to 50% at idle (fluctuating).

Make sure the engine is not heating up too much idling all the time during the adjustments!

2) EHA current check:

After the duty cycle has been adjusted to 50% (fluctuating) at idle the EHA current is checked like this:
  • Above mentioned vacuum line of the fuel evaporation system still pulled off and blocked.
  • Pull the plug off the EHA and connect the amperemeter in series between the plug and the EHA.
    (one measuring cable connected to one of the EHA terminals and the other one connected to the corresponding terminal on the plug. The other EHA and plug terminal bridged with a short cable)
  • After turning the key to “ignition on” the meter should read +20 mA (static).
    (If the value is negative: change the polarity of the meter’s measuring cables)
  • Start the engine and let it idle.
  • Wait until the o2 sensor is warm enough and starts to work (you’ll see that by fluctuating amperage).
  • Then the current should fluctuate within 0 +/- 3 mA both at idle and at 2000 rpm.
  • If that’s the case, the EHA adjustment should not be changed and the differential pressure can be checked according to step 4).
3) mechanical / hydraulic adjustment of the EHA:

If the mean value of the amperage at 2000 rpm lies beyond the range of 0 +/- 3 mA, then - with new o-rings for the EHA provided - adjust the EHA like this:
  • Remove the EHA from the fuel distributor (best with a rag wrapped around the EHA when you loosen the bolts to prevent fuel from being sprayed around due to the fuel pressure).
  • Remove the slotted plug srew on the backside of the EHA - behind that you’ll see a small hexagon srew.
  • If the current at 2000 rpm was too far positive: turn the hexagon screw maximum 60° counterclockwise.
  • If the current at 2000 rpm was too far negative: turn the hexagon screw maximum 60° clockwise.
  • Reinsert the small slotted screw.
  • Reinstall the EHA (with the new o-rings).
  • Repeat the procedure up from step 1 with the air filter installed and the engine at its normal operating temperature, until the EHA current at 2000 rpm fluctuates within the range of 0 +/- 3 mA.
I recommend to record the total angle change of the hexagon screw.


4) differential pressure check:

If the EHA current at 2000 rpm fluctuates within the range of 0 +/- 3 mA check the fuel pressure like this:
  • The engine must be at it’s normal operating temperature.
  • Pull off the leakage hose at the fuel pressure regulator to check for fuel leakage. If fuel comes out, the membrane in the pressure regulator is damaged and a pressure test superfluous. In that case the pressure regulator must first be replaced.
  • Check the leakage hose - it should not be blocked or kinked. Although the hose plays no role in the function of the pressure regulator, it being blocked or kinked would impair it.
  • Reattach the hose.
  • Detach the cold start valve pipe from it’s port at the fuel distributor.
  • Connect the manometer to that port (make sure it's safely fixed!).
  • Start the engine and check the pressure. It should be 77 - 80 psi (system pressure)!
    If it’s higher, there is either a problem with the pressure regulator or the fuel return pipe to the fuel tank (blocked or crimped).
    If it’s lower, there’s (besides possible external leaks) either a problem with the pressure regulator, the accumulator, the filter(s) or the pump(s).
  • Stop the engine and reconnect the cold start valve pipe.
  • Remove the plug srew at the side of the fuel distributor (next to the short pipe which goes to the pressure regulator) and safely! connect the manometer to that port (tapped hole in FD: M8 x 1) to measure the differential valve’s lower chamber pressure.
  • Start the engine and let it idle.
  • Pull off the EHA plug before the o2 sensor starts to work and watch the manometer. The pressure should be 4.5 – 6.5 psi lower than the system pressure meassured before!
  • Watch the manometer while you reconnect the EHA plug. There should be no difference in pressure!
  • Briefly rise the engine’s speed to about 3000 rpm and watch the manometer during the engine’s speed decline (to about 1300 rpm). The pressure should rise to the system pressure measured before! (overrun switch-off).
  • Pull the plug of the CIS-CTS (coolant temperature sensor which gives input to the CIS-ECU) and connect a 2.5 kΩ axial-lead resistor to the plug instead of the CTS, to simulate an engine temperature of 20°C (68°F).
  • Watch the manometer and up from idle jerkily rise the engine’s speed to about 3000 rpm. During the acceleration the pressure should drop to about 55 psi! (acceleration enrichment).
  • Reinsert the plug srew into the fuel distributor.
Lower chamber pressure values different from the above-mentioned values while the system pressure is within specification doesn’t necessarily mean there is a problem with the EHA or its adjustment. That could also indicate a problem within the fuel distributor.


After the EHA adjustment is done, I suggest to set the duty cycle to fluctuating around about 47%.

Don’t forget to reconnect the hose of the fuel evaporation system!

H.D.
 

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How much is this knowledge worth?

Very detailed. Impressive

Thanks for taking the time to wiite this up.
 
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