Calling all D-Jet hoarders! - Page 2 - Mercedes-Benz Forum

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post #11 of 23 (permalink) Old 10-21-2014, 04:42 AM
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How is a leaner mixture adjustment carried out? Special instrument/tool?
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post #12 of 23 (permalink) Old 10-26-2014, 04:54 PM Thread Starter
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epilogue

ok - everything is better now in d-jet land

dgosh28 was nice enough to sell me a spare MPS and now the engine is running good again

I did try tweaking the adjustment screw on the broken one but that had no effect on the sensor's ability to hold vacuum. If it doesn't hold vacuum, it's not going to work. The adjustment screw can richen/lean the fuel/air mix but I would not recommend fooling around with it as it is pre-set when it's made.

So if your 4.5 l engine is spewing black smoke and all of your spark plugs look like this

Calling all D-Jet hoarders!-20141025_163600.jpg

it could be a faulty MPS. The factory manual mentions testing the sensor for electrical resistance but makes no mention regarding the vacuum test.

The takeaway here is that the MPS can go bad - they're 40 years old after all. Repairing one of these doesn't look easy to me, the rivets have to be drilled out and you'd have to rig something up to repair the cells or diaphragm and then put everything back together again -- all that effort is not worth my time. Maybe I'll tear apart the broken one to see how it works.

Now onto other things
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post #13 of 23 (permalink) Old 10-31-2014, 12:27 PM
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This seems to be a D-Jet hangout so maybe I can get the info I need here. Trying to find out at what points in the crankshaft cycle the triggering points send their pulses to the ECU. I have an M110 but the V8 should be the same just fires 4 injectors instead of 3. Any info appreciated.
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post #14 of 23 (permalink) Old 10-31-2014, 12:51 PM
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Originally Posted by 107merc View Post
This seems to be a D-Jet hangout so maybe I can get the info I need here. Trying to find out at what points in the crankshaft cycle the triggering points send their pulses to the ECU. I have an M110 but the V8 should be the same just fires 4 injectors instead of 3. Any info appreciated.
My understanding is that there are four contacts in the v8 trigger points, and the v8's inject fuel in sets of 2 cylinders/injectors that juice at the same time. My understanding is that the 6 has only two contacts, and three cylinders/injectors juice at the same time. Does that sound about right?

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post #15 of 23 (permalink) Old 10-31-2014, 01:09 PM
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D-jets have 2 sets of triggering points. 4 cylinder engines fire in 2 sets of 2, 6cyl. fire in 2 sets of 3, 8 cyl. fire in 2 sets of 4. M110 ties 1-3-5 together and 2-4-6 together. Not sure about the V8.
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post #16 of 23 (permalink) Old 10-31-2014, 01:21 PM
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D-jets have 2 sets of triggering points. 4 cylinder engines fire in 2 sets of 2, 6cyl. fire in 2 sets of 3, 8 cyl. fire in 2 sets of 4. M110 ties 1-3-5 together and 2-4-6 together. Not sure about the V8.

So I would assume there are two numbers you are seeking. But there is surely a duration that the trigger points are in contact. Just curious, are you seeking the midpoint, duration, etc?

Sounds like an interesting quest.

Maybe Porsche and Other brand forums have some info on this too.

.

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post #17 of 23 (permalink) Old 10-31-2014, 05:02 PM
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Originally Posted by Fonzi View Post
So I would assume there are two numbers you are seeking. But there is surely a duration that the trigger points are in contact. Just curious, are you seeking the midpoint, duration, etc?

Sounds like an interesting quest.

Maybe Porsche and Other brand forums have some info on this too.
Fonzi, I should have read up on 8 cylinder D-jets as they certainly do have 4 sets of triggering contacts and 4 output leads. All my D-jet books including Bosch says they fire in 2 groups, 2, 3 or 4 injectors per group. If they fire in groups of two, that would be semi-sequential, didn't think that came along till Motronic. Wonder why the 6 didn't get it?? Now I don't know what to think. As for my other question I went ahead and graphed it out. Will post as soon as I have a decent chart.
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post #18 of 23 (permalink) Old 11-11-2014, 01:05 AM
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You can use MAP # 0280100112 which is the same for M117 engines and I believe it would be little cheaper as you stay away from W 108/109/112 /113 as some guys they use these on e bay to make it better selling and more gain
cheers
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post #19 of 23 (permalink) Old 11-11-2014, 05:05 AM
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You can use MAP # 0280100112 which is the same for M117 engines and I believe it would be little cheaper as you stay away from W 108/109/112 /113 as some guys they use these on e bay to make it better selling and more gain

cheers

I suspect you mean w108/109 and w111/112 (not w113 which never came with a v8). Correct?

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post #20 of 23 (permalink) Old 11-11-2014, 06:13 AM
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you are right Fonzi what I meant here there are common parts for different MB the extreme hot expensive is W 112/113 and 100 but you can find the same in different MB models.Same the MAP for 2.8 you can search it for w 108 cheaper than searching for W 113 particular .and MAP for W 116 3.5 or 4.5 will be cheaper than searching for w 108/109 3.5 or 4.5 as an example only.
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