Further R107 D-Jet frustration

Thanks!

I will do my tests again later when I am in my garage.

Regards

" Hi, this sounds like something I have seen a few times: "I was now really struggling until one day I unplugged the Engine Coolant Temperature sensor (ECT). The car started and would run and drive, but excessively rich. I tracked down and bought a new ECT sensor (potentially the last one in Mercedes North America's inventory). I installed this and plugged it in and, of course, the car would not run. If I unplug it the car will again run....." Make sure the air sensor (I) and (II) coolant sensor leads are plugged  into the right places. I have seen them swapped about before.
Cheers! RonB.

Hi Ron,

This is a fair point, but I've tested through from the ECU and they are certainly pointing at the right sensor.

Interestingly, I just Googled my symptoms again (a daily routine) and one similar question was posed by a Ron B on a Mercedes forum back in 2002... I guess that must have been you!

My next step is to start cleaning every ground connection I can find. The ECT sensor is almost certainly grounding out when connected. This is all very frustrating!

Hi Jetronic.org,

I thought I should update this with a positive conclusion in case it is of any help.

I eventually found a friend with a MAP sensor I could borrow, in this instance from a Porsche 914, however to all appearances it is the same unit.

I connected this MAP sensor and re-connected the ECT sensor and the car started immediately and ran very well. This helped rule out a fault in the wiring of the ECT sensor. A replacement MAP sensor (with a warranty) was sourced from Fuel Injection Products in California and I installed it today. The car now runs properly again.

The lesson here is, as pointed out by the experts, that you can test for resistance on both coils and test for vacuum and these values may be correct, however it is difficult, or impossible, to measure the operation of the unit when the car is running and there seems to be no data to compare to even if you can rig up a test.

Thanks for all your help. I have now sold the car!

Jeff