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· Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
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I canNOT wait to carefully read this. Thank you, H.D.!

Okay, have read it and am letting it soak in. Great write up, H.D. I really appreciate your taking the time to do this. It's an excellent resource document.
 
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· Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
Joined
·
5,693 Posts
I’d like to reemphasize something I already addressed in post 2 of this thread.

In several threads I read that members simply readjusted the duty cycle because it was too high / low when they checked it. … Following my driving-along-the-road metaphor from post 1 that’s like loosening the steering wheel’s locknut and changing the wheel’s position because it’s not straight on a straight road, without caring about possible reasons like uneaven tyre pressure, sticking brake pistons, damaged steering mechanism, ...

Translated to the KE-Jetronic: If the duty cycle is out of tune, there’s a reason for that, and with a probability bordering on certainty it’s not related to the adjustment screw, unless someone fiddled around with it. Maybe there’s a fuel pressure problem, or a leaky CSV, or a false air leak, … … just to mention a few problems which influence the duty cycle ... and which would still be there after simply readjusting it.

The duty cycle should primarily be seen as diagnostic information ... not only when it shows a static error code, but also when it fluctuates !
While that information is too often neglected, IMO, I always wanted access to it (plus other info) at the touch of a button anytime during driving or parking, and the picture below shows a device which provides that. I built it into the ashtray of my 300CE, when it was less than half as old as it is now.

Also, IMO, too often neglected is the information fuel pressure tests (particularly lower chamber pressure tests under specific conditions) can provide … best supplemented by simultaneous EHA current tests (of course, with the EHA adjustment screw not having been fiddled with !) … and, even better, also supplemented by simultaneous closed-loop o2 sensor voltage tests.
These tests in addition to the duty cycle test, can be very informative … of course, with the duty cycle adjustment screw not having been touched, at least not after a problem started ! … :wink_2:

Look at the KE-Jetronic as a playground for diagnostic thinking, instead of replacing parts which are not diagnosed faulty … increases the enjoyment of “golden era“ MBs … and maybe you want to give a device like the one I made some thought … facilitates diagnosing problems with the OVP, FPR, CPS, o2-sensor, AFM-POT, TPS, CTS, and other parts immensely … especially if they’re intermittant. … :wink_2:

H.D.

P.S.: I apologize in advance if I don‘t notice further posts / questions, which might happen because I‘m not receiving (required) email notifications from Benzworld anymore.

H.D.

I love the idea of the feedback gauge. Do you have records or instructions of how you did it?

As if I'm going to add this to my list of 'to do's'. Well, I'd still love to see the info. It's a great idea.
 

· Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
Joined
·
5,693 Posts
Two of the most commonly made CIS-E-related mistakes...H.D.
H.D., Can't thank you enough for this info. I'm doing a lot of studying these days to get my head wrapped around this system and your comments always add to my education.

Thanks so much for taking the time and making the effort to share.
 
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