Jetronic KE expert anyone ??

[Philbask]

Running out of ideas myself, need to know why ECU would appear to work correctly at cold start / start-up / over-run but normal driving it keeps ramping EHA current to minus 10 mA ??

 

[Marku]

Only got info on the d-jetronic if its of any help will have a look through the manual.

 

[Philbask]

Thanks Marku, any info appreciated... can't for the life of me come up with a set of circumstances that would cause the ECU to drive the output to the EHA to plus 10mA or minus 10mA ?!?

 

[219]

One thing that can cause temperature related issues on these cars is failure of the heat sink compound bonding the EZL unit to the inner wing .

When this ages , heat is no longer transferred away , causing the EZL to overheat and , ultimately , fail .

The fix is just removal of the unit , cleaning of both surfaces and replace the compound .

Inner wings rotting away and leaving no metal to sink heat into doesn't help either

 

[chrisd87]

This is a total stab in the dark, but could the oxygen sensor be faulty? Could it be giving the ECU incorrect information about the mixture strength, which the system is then trying to correct using the EHA?

It probably wouldn't do any harm to test all of the system's sensors one by one. Unless the ECU itself is duff, it sounds rather like it's being fed incorrect information from somewhere - you just need to identify the source.

 

[SL300-24]

Always difficult to diagnose like this but a couple of questions for you...

Have you measured the duty cycle and what readings did you get/

Did you measure the eha current using a Mercedes break-out cable?

 

[Philbask]

Thanks for all the responses guys,

I don't think EZL / ignition issue, all works fine apart from the current being sent to the EHA at certain times.

Re O2 sensor, tbh I have not had a chance to get on the ramps yet (oh, various other things getting in my way atm!!) but I am not 100% sure it has one?! It may be running open loop, if there is one, with you on that, disconnection should prove pretty quickly, hoping for a chance to check this Thursday,,,,,

Duty cycle, no, my available meters do not measure frequency I'm afraid, the EHA current is measured with my own cable adaptation (and yes it is rock solid, 30+ years an instrument engineer )

Again, thanks for all the advice, deffo think I need to identify the existence of a Lambda sensor first and foremost ! (time is my enemy just now )

 

[SL300-24]

Pull up the drivers side carpet, you will see the connecting plug for the lambda sensor under there (you will have one), at the back near the seat. Unplug it and see if it makes any difference. You really need to be able to measure duty cycle to diagnose properly or you will be component changing. It can be done by calculating voltage this may be of help.......



http://www.landiss.com/mixture.htm

 

[Philbask]

Excellent SL300-24, many thanks, that looks really useful and I will get on it asap now! (with great hope and expectation ;-) )

 

[SL300-24]

Good luck, let us know how you get on...

 

[Philbask]

Well, possibly a breakthrough !!! With the Lambda disconnected I have seen no occurrences of the ramp to plus or minus 10mA (yet !, only been today..) So will leave as is until the weekend to prove beyond reasonable doubt and order a replacement. Still then intend to leave the EHA meter connections in place to see what happens with a good unit in place, also will try the duty/cycle measurement, will be interesting!!!
Thanks for all comments / advice given (just knowing where the O2 connector was has saved me sooooo much time