Unplug one wire engine started running even worst, two wires out its stop running at all. I guess my ECU works good.

Your engine doesn't though. With the EDS solenoid unplugged, the idle should be ~500 RPM. If the engine won't idle that low, you have some severe mechanical problems or the IP is seriously out of adjustment.

The EDS solenoid on the back of the IP is a 2-pin plug. Not sure how you unplugged one wire or another, but it's unimportant - if you unplugged EITHER of the pins on the EDS solenoid, it should have had the same effect - low RPM.

Oops! A Mistake!
 

Just a 2018 update to this thread, I made a mistake on one of the capacitor values! The 7µF is actually a 1µF!

When I originally recapped my ECU, the top was split open on most of my caps. They were those crappy brown "UK" caps that ALWAYS die (seriously, if you see one in any of your car's electronics, just replace it, they're crap!). Because the font is extremely hard to read, I assumed it was a 7µF, especially due to the size of the capacitor.

Flash forward to today, and I was reworking an ECU for a friend's SDL and noticed his was a 1µF of a different brand. Same board, same layout, same design.

I've fought an intermittent idle hunt that's been significantly worse since I tuned the injection pump....at an idle it's like someone rhythmically goosing the throttle, and it isn't always present, but will show up at some point every time the car is driven. Since changing that capacitor to a 1µF, it idles rock steady, no hunt at all!

This thread is old enough that I can't go back up and edit the original post, so hopefully future readers will make it this far and notice the update.

I have been dealing with 603 powered vehicles for many years and have had this issue on several cars and could never figure out what it was. This is great info.

This is MY SDL in question BTW guys.! :D



Late timing cover ordered. No 17 head receiving full rebuild. Guides, OE valves, springs, stem seals. This is very exciting news on my end. :D

EDS/ELR
 

Where is this solenoid and cm box on a 93 w140? Would these idle symptoms be the same ? My ac blows cold and works great but initial start up is rough idle.

The main symptom this box was giving is a lope at idle, like someone fiddling with the rack lever and goosing it in a rhythmic cycle. A rough idle when cold is unlikely to be the EDS system, you can easily enough test the theory. Unplug the 2 pin connector on the big red solenoid on the back of the injection pump and start the car. Idle speed will be ~500-550. If your roughness continues, the EDS system has nothing to do with it and you have mechanical, glow plug, injection, or compression issues.

Ok, Would smoke be in the mix with all this? #2 had a pc leak, I installed a new one but it's still not smooth,better though. Also saw lots of black liquid when I did a diesel purge. Its somewhat better but still not clear in the bottle, have to continue. I pulled the ETR pin, ng car barely ran if at all. While upon inspection I noticed oil and some coolant residue around #1 intake manifold port,coolant thermostat neck area. It's losing oil, and it's making its way down the head and block, that could be why? Also turbo at intake has oil in it, a small line. The impeller is not freewheeling more on the tight side with no play. Time for a compression test?. Sad because everything works Hvac is very nice both heat and ac. It's a florida w140 and needs very little body wise to be mint. Interior is almost perfect. If motor is ng Id like to do a 606 st with matching trans.. It would be the ultimate concrete living room.

I read page 2 of this thread bought the caps, went to replace them and found the 1µF instead of 7µF... then I went on to read page 3. Lesson learned lol. Fortunately I had a 1µF cap in my stash. No worries.

I figured that would happen to someone at some point. By the time I found the issue, the thread was old enough that it wouldn't let me change the original posting. :mad:

No worries, I really appreciate the write-up and now my idle is dead steady all the time.
:drink:

Eric is a good dude, fixed my box right up. Did my SD's also because he is just that sadistic!

I know this is an ancient thread but I was happy to see someone went through recapping the EDS. I fix 1970s stereos as a hobby so the EDS was fairly simple to do, though it is a double sided PCB so you have to be careful. I was amused to see that the caps Mercedes was using in the 80s were the same as B&O and McIntosh in their stereos, of course they're all on my list of junk-replace immediately before they fail.

That being said I replaced the 5 capacitors in mine, a few had drifted quite a bit but none were completely dead. The 4 on the bottom board and 1 on the top board.

Unfortunately the recap does not seem to have entirely fixed my idle issue. Before the capacitor replacement the ELR adjustment did absolutely nothing, now it does actually adjust idle. However once I start driving if the revs are 2k or higher when they drop back down fast the engine drops down to 500 or so RPM and comes back up to 530 or so. Only when coming off the gas slowly does the idle set by the ELR stick. It also was still occasionally sticking at a higher (800-900) RPM idle both before and after the work

I'm wondering what other components go into this idle adjust, maybe I just have a relay that's acting up or something.

Would you repair others?? I have a few.


How stiff is the throttle linkage? I had a 603 in a w140 that would actually go higher than throttle because of a stiff cruise control actuator.

I wouldn't necessarily be opposed to it, it's easy work, just 5 capacitors and some solder connectors to reflow. My only concern would be I don't have much of a way to test the board for function. I would assume back in the day Bosch had a test jig for these to test all the functions.

I'll have to take a look at the throttle linkage. I haven't done the cruise control amp yet as I am relatively new to these vehicles and afraid to tear things too far apart.

We generally have a shop so most of the mechanical work for us due to a lack of mechanical experience and time on my end. just have the skill set to replace capacitors and find bad solder joints.