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Further R107 D-Jet frustration

  • jefflemons
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21 Aug 2021 23:04 #16780
von jefflemons Americas (USA / CAN) Mercedes-Benz R107 450 SL
Further R107 D-Jet frustration wurde erstellt von jefflemons
Hi Jetronic Forum,

A few months ago I reached out and received an enormous amount of excellent help when my D-Jet R107 simply stopped working. I'm still experiencing problems - perhaps the solution is here!

For some months, having previously ran fine, the car would not run. As soon as the cold start injector closed the car would die. We found that this was due to an almost fully-lean fuel condition. The injectors were getting a signal to fire, but were not open sufficiently long enough to provide sufficient fuel.

Using the troubleshoot checklist (many times), testing at the ECU end of the wiring,  I am quite confident that I confirmed that all readings were correct. I obtained (from Nordfisch) the trigger point gap tool and used this. Still no run.

I concluded that the ECU was faulty and bought a warranted refurbished unit from a reputable USA supplier. Still no start! An expensive assumption!

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. 

So, perhaps someone has an idea? The car will run (rich) with the ECT sensor unplugged but dies if it is plugged in. Is there a fault in another component which unplugging the ECT is compensating for? Shorting the two wires for the ECT has the same effect as plugging it in to the brand new ECT.

To conclude - the ECU is new, the ECT is new, the readings i take at the ECU connector seem to be within boundaries. 

Any help would be gratefully received!

 

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  • nordfisch
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22 Aug 2021 00:14 #16781
von nordfisch Europe Opel Diplomat 2.8 E
nordfisch antwortete auf Further R107 D-Jet frustration
Hi Jeff,
my only idea is the wiring could be faulty somehow. Don't know how, but it can't be the sensor itself.

Could you remove the plug from the sensor and apply a resistor (1/4 Watts will do) directly to the wire 23 (blue/white) at the ECU-plug, the other side towards 11 (brown) and try again?
You should choose the resistor following the engine temperature,
0° C 32° F 5,9 kOhm
20° C 68° F 2,5 kOhm
40° C 104° F 1,2 kOhm
60° C 140° F 600 Ohm
80° C 176° F 325 Ohm
100° C 212° F 190 Ohm
The resistor has not to be a perfect fit for this check, just don't choose a value too far away from the engine temp.

Regards
Norbert

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  • jefflemons
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22 Aug 2021 01:21 #16783
von jefflemons Americas (USA / CAN) Mercedes-Benz R107 450 SL
jefflemons antwortete auf Further R107 D-Jet frustration
Hi Norbert,

I will try this. I will probably not be able to buy an appropriate resistor until Monday, but will do so and report back.

My other idea is that some other component is at fault, sending a wildly inaccurate reading, and that by unplugging the ECT it is somehow compensating the other way. However, I am inclined to agree that this may be a wiring issue.

Thanks for the advice!

Jeff

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  • Dr-DJet
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  • Mercedes-Benz R107 450 SL, Mercedes-Benz W111 280 SE Cabrio
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22 Aug 2021 13:27 #16785
von Dr-DJet Europe Mercedes-Benz R107 450 SL, Mercedes-Benz W111 280 SE Cabrio
Dr-DJet antwortete auf Further R107 D-Jet frustration
Hi Jeff,

I have one suspicion: It is a crazy US tradition to "tune" 450 MAP sensors. That normally ends up in total failure. Even if your car's MAP sensor was not touched, it sounds similiar.

Unfortunaltely it does not seem possible to buy a MAP sensor 0 280 100 100  in the USA in proper shape. Since years I have not had a single such MAP sensor in my hands that was not completely detuned.  Second problem is that by aging they start to change behaviour. If is is now totally lean engine coolant temp sensor will help to get it running. But that makes a 3-fold richer mixture which is too much.

Just a suspicion but I guess one you should check by sqapping MAP sensor with someone who has a properly running engine.

Viele Schraubergrüße - best regards, Dr-DJet Volker
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22 Aug 2021 18:28 #16791
von jefflemons Americas (USA / CAN) Mercedes-Benz R107 450 SL
jefflemons antwortete auf Further R107 D-Jet frustration
Hi Volker,

This makes a lot of sense - finding a working D-Jet Mercedes MAP sensor to "try" here in Western Canada might be a bit of a challenge. I may speculatively buy another used item to see if any change is made, which may at least allow me to pinpoint the cause of the issue.

As with Nordfisch, I will report back!

Thank you

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  • Dr-DJet
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22 Aug 2021 18:42 #16794
von Dr-DJet Europe Mercedes-Benz R107 450 SL, Mercedes-Benz W111 280 SE Cabrio
Dr-DJet antwortete auf Further R107 D-Jet frustration
Hi Jeff,

you can forget buying a working 0 280 100 100 on eBay. They are alĺ without black cap, sold as core, ... and for sure detuned. You have to find someone nearby with a working one that you can swap for a test.

I repeat that I have not seen a single working one in last years and retuned plenty of them.

BUT: This is just suspicion!

Viele Schraubergrüße - best regards, Dr-DJet Volker
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01 Sep 2021 03:26 #16850
von jefflemons Americas (USA / CAN) Mercedes-Benz R107 450 SL
jefflemons antwortete auf Further R107 D-Jet frustration
Hi Volker,

I have (probably) located a "warranted" good MAP sensor from fuelinjectionproducts.com however, I am reluctant to spend the expected $450USD (more for me - I'm spending $CAD!!) unless I know this is the issue.

I am skeptical - this afternoon again I tested my current MAP sensor: both resistances are correct (90 and 350) and the unit holds vacuum.

I tried a little experiment: With the ECT sensor disconnected (the car will NOT run if it is connected, without exception) I disconnected the vacuum line to the MAP sensor and installed my hand-pump vacuum tester. I applied around 0.5 bar of vacuum and started the car. It ran as usual. I gently increased the vacuum to around 0.7 bar and the revolutions increased a little. At 0.7 bar it held its vacuum for a long time. Plugging the ECT sensor back in this condition of course caused the car to die.

At the ECT sensor plug one terminal goes to ground and the other does not. Am I to assume the wiring here is OK?

I realise this is all a bit confusing but I am really at a loss at what to do without throwing $100s++ at components just to see if they help!

J.

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01 Sep 2021 10:33 - 01 Sep 2021 10:38 #16851
von Dr-DJet Europe Mercedes-Benz R107 450 SL, Mercedes-Benz W111 280 SE Cabrio
Dr-DJet antwortete auf Further R107 D-Jet frustration
Hi J??? ,

if you search on this website you will find reports where this company was not praised for its performance on MAP sensor tuning and repair. Just recently a BMW case.

I really recommend you find someone with a 450 SL/C or W108 280 SE 4.5 or 450 SE / SEL around you and swap it. I have a whole pile of 0 280 100 100 MAP sensors lying here that were "raped". I recently had a case where such a MAP sensor had a strange black cap, rivets were removed and replaced by M5 screws and when I tried to adjust it I had to give up as inner components were also swapped resulting in a completely wrong curve. I will most probably see another such case next weekend during our grease monkey come together.

It is a nightmare to see what Americans do to those MAP sensors.

Just an example of a "tested" MAP sensor on ebay . God help us!

Viele Schraubergrüße - best regards, Dr-DJet Volker
Mercedes-Benz 107 SL/C in der SLpedia Sternzeit 107

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Letzte Änderung: 01 Sep 2021 10:38 von Dr-DJet.

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03 Sep 2021 19:55 - 03 Sep 2021 19:56 #16862
von jefflemons Americas (USA / CAN) Mercedes-Benz R107 450 SL
jefflemons antwortete auf Further R107 D-Jet frustration
Hi Volker,

Here in Canada (not to be confused with the USA…) we have a significant deficit of D-Jet cars available for me to borrow parts so, in the name of science, I continue to try and diagnose rather than buy parts “just in case” they work. Like you, I’m looking at MAP sensors on EBay USA and have very little confidence!

So, a quick question. At the ECU connector I find a resistance value (c. 2.5kOhm) between pin 23 (ECT) and pin 1 (air temp). In my head there should be no connectivity between the two at all. This resistance is about the same as between 23 and 11. Could this possibly be the source of an electrical short? Any ideas?

Thanks for your help so far,

Jeff
Letzte Änderung: 03 Sep 2021 19:56 von jefflemons.

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03 Sep 2021 20:11 #16863
von Dr-DJet Europe Mercedes-Benz R107 450 SL, Mercedes-Benz W111 280 SE Cabrio
Dr-DJet antwortete auf Further R107 D-Jet frustration
Hi Jeff,

as both are connected to ground (11), you measure both in series.

Viele Schraubergrüße - best regards, Dr-DJet Volker
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03 Sep 2021 21:22 #16864
von jefflemons Americas (USA / CAN) Mercedes-Benz R107 450 SL
jefflemons antwortete auf Further R107 D-Jet frustration
Hi Volker,

I'm not sure that answers my question.

Indeed I can measure Pin 1 against Pin 11, and Pin 23 against Pin 11, but in my quest to find the fault in my system I decided to try Pin 23 against all the other pins in an attempt to find a possible short/wiring fault. I measured a resistance value between (of course) Pin 11 and then again at Pin 1.

As Pins 3,4,5,6, 16 and 24 also measure measure against Pin 11 would, by your logic, I not expect to see a resistance value when testing Pin 23 against 3,4,5,6,16 and 24 also?

I try to ask as few questions as possible, and have followed very closely all troubleshooting methods detailed on this excellent site, however with all components testing within the correct range I am really struggling to get this otherwise immaculate 450SL running with the ECT sensor connected.

The MAP sensor coils both show correct resistance and the diaphragm holds vacuum with no loss. By all accounts it is OK. Is there anything else I can test for?

Thanks

Jeff

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03 Sep 2021 22:06 #16865
von Dr-DJet Europe Mercedes-Benz R107 450 SL, Mercedes-Benz W111 280 SE Cabrio
Dr-DJet antwortete auf Further R107 D-Jet frustration
Hi Jeff,

correct pins 3-6 should also show engine temp resistor when measured to pin 23. Injectors only have 2.4 ohms.

Viele Schraubergrüße - best regards, Dr-DJet Volker
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03 Sep 2021 23:23 #16867
von jefflemons Americas (USA / CAN) Mercedes-Benz R107 450 SL
jefflemons antwortete auf Further R107 D-Jet frustration
Thanks!

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

Regards

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  • BenKraft
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04 Sep 2021 02:20 - 04 Sep 2021 02:22 #16869
von BenKraft Australia Mercedes-Benz C107 350 SLC, Mercedes-Benz C107 450 SLC, Mercedes-Benz W108 280 SE/L 3.5, Mercedes-Benz W109 300 SEL 3.5, Mercedes-Benz W111 280 SE 3.5 Cabrio, Mercedes-Benz W114 280 CE, Mercedes-Benz W114 280 E, Mercedes-Benz W116 280 SE/L, Mercedes-Benz W116 450 SE/L, Volkswagen Typ 3 1600 E
BenKraft antwortete auf Further R107 D-Jet frustration
" 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.
Letzte Änderung: 04 Sep 2021 02:22 von BenKraft.

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07 Sep 2021 08:38 #16878
von jefflemons Americas (USA / CAN) Mercedes-Benz R107 450 SL
jefflemons antwortete auf Further R107 D-Jet frustration
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!

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26 Okt 2021 02:44 #17088
von jefflemons Americas (USA / CAN) Mercedes-Benz R107 450 SL
jefflemons antwortete auf Further R107 D-Jet frustration
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

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