560SL "Japan" poor running engine, PROBLEM SOLVED!

A second fault was found. The temperature sensor is broken (green 2 pin-sensor with 2 round seperate plugs above intake manifold). It shows 8200ohm resistance, at 7°C watertemperature (ambient temp after 24h) which is much too high. At 90°C I still measure almost double the required resistance. (410ohm measured, 247ohm required). It means that the EHA receives a signal to enrichen the mixture at a time when it is not required.
Next tuesday I will replace, and report.

 

I have received the new temp-sensor, and installed.
Idle is very good, and stable at 750rpm, in park, but problems as described before, are not gone.

I measured the resistance between pins and ground, and it was 250ohm at 90°C.

Elsewhere, I read that you can unplug the ECU, to effectively make a k-jetronic (purely mechanical injection) out of a ke-jetronic.

So I did just that.

Car started quite difficult, but then held idle. The problem with revving was worse, but did show the same symptoms; car did rev a bit when slowly pushing the throttle, but bogged when quickly pushing the throttle.

If the problem would be elektronic, then I would think that detaching the ECU would ameliorate the running, but it did not.

So I guess the ECU and EHA are trying their best to provide a correct mixture, but, once the throttle is openend quickly and suddenly, the systems seems unable to "follow that input."

I have ordered a obd1 scanner (I have the rectangular 8 pin diagnostic port), so I will be able to measure faults.
I will also buy a multimeter with duty-cycle measurment, to see what I can measure.

And then we can start all over again....

Well, I don’t see what eventually was the problem here. In my opinion, one of the very first tasks to undertake is a smoke test. You can’t very well achieve reliability of results with one or more vacuum leaks.

Hello,
I thought this thread was sleeping
I performed a vacuum-smoke test a while ago, that uncovered a few small leaks (the most obvious was a leak at the throttle plate axle) but nothing serious.
The SL is at a specialist workshop now.
They have uncovered a substantial fuel-leak at the plunger of the air-flow plate.
The complete assembly was removed, and sent to a renovation specialist, but after new installment, the plunger still leaks.
The mechanic has now installed a replacement air-flow assembly with a non-leaking plunger, to see if that is the source of the problem.
But it has clearly been determined that the problem is mechanic, and not electronic.
furthermore, the distribution-chain and guiderails have been replaced as well. They showed a slack of 7,5 degrees, with a maximum of 9 degrees allowed by the factory manual.
 

It has taken blood, sweat and tears, not to mention a few pedantic people on this forum, but the problem with my 560SL "Japan" has been solved!
The head-mechanic at the specialist where my SL is now, decided to change out the fuel-distributor and "luftmengenmesser" (with test-examples at the garage) because the plunger in the distributor still leaked after revision. 
But not only that, he also blocked of the fuel-feed to the cold-start-injector.

Apart from fine-tuning, the bogging or refusal of the engine to rev up after warm-up has been cured!!.

It is still difficult to understand what exactly went on in the inlet-trajectory, but the leak at the plunger combined with an apparant leak at the cold-start-injector caused the mixture to become so rich that there was no combustion possible anymore, especially when entering air sucked in fuel and fuel-vapors which accumulated in the inlet. When only slightly pressing the throttle, less air was introduced, so it sucked up less accumulated fuel and vapors, and as such, the engine did rev up a bit. 

I hope that my diary write-up can be of help to some-one else whe experiences the same symptoms, and seeks advice!

To everybody on this forum, even the so-called professionals who have forgotten to think instead of following procedures, thank you very much for your help!!

Greetings

Gunter